# class String

A `String` object has an arbitrary sequence of bytes, typically representing text or binary data. A `String` object may be created using `String::new` or as literals.

`String` objects differ from `Symbol` objects in that `Symbol` objects are designed to be used as identifiers, instead of text or data.

You can create a `String` object explicitly with:

- A string literal.

- A heredoc literal.

You can convert certain objects to Strings with:

- Method `String`.

Some `String` methods modify `self`. Typically, a method whose name ends with `!` modifies `self` and returns `self`; often, a similarly named method (without the `!`) returns a new string.

In general, if both bang and non-bang versions of a method exist, the bang method mutates and the non-bang method does not. However, a method without a bang can also mutate, such as `String#replace`.

## Substitution Methods¶ ↑

These methods perform substitutions:

- `String#sub`: One substitution (or none); returns a new string.

- `String#sub!`: One substitution (or none); returns `self` if any changes, `nil` otherwise.

- `String#gsub`: Zero or more substitutions; returns a new string.

- `String#gsub!`: Zero or more substitutions; returns `self` if any changes, `nil` otherwise.

Each of these methods takes:

- A first argument, `pattern` (`String` or `Regexp`), that specifies the substring(s) to be replaced.

- Either of the following:

  - A second argument, `replacement` (`String` or `Hash`), that determines the replacing string.

  - A block that will determine the replacing string.

The examples in this section mostly use the `String#sub` and `String#gsub` methods; the principles illustrated apply to all four substitution methods.

Argument `pattern`

Argument `pattern` is commonly a regular expression:

    s = 'hello'
    s.sub(/[aeiou]/, '*') # => "h*llo"
    s.gsub(/[aeiou]/, '*') # => "h*ll*"
    s.gsub(/[aeiou]/, '')  # => "hll"
    s.sub(/ell/, 'al')     # => "halo"
    s.gsub(/xyzzy/, '*')   # => "hello"
    'THX1138'.gsub(/\d+/, '00') # => "THX00"

When `pattern` is a string, all its characters are treated as ordinary characters (not as `Regexp` special characters):

    'THX1138'.gsub('\d+', '00') # => "THX1138"

`String` `replacement`

If `replacement` is a string, that string determines the replacing string that is substituted for the matched text.

Each of the examples above uses a simple string as the replacing string.

`String` `replacement` may contain back-references to the pattern’s captures:

- `\n` (n is a non-negative integer) refers to `$n`.

- `\k<name>` refers to the named capture `name`.

See `Regexp` for details.

Note that within the string `replacement`, a character combination such as `$&` is treated as ordinary text, not as a special match variable. However, you may refer to some special match variables using these combinations:

- `\&` and `\0` correspond to `$&`, which contains the complete matched text.

- `\'` corresponds to `$'`, which contains the string after the match.

- `\`` corresponds to `$``, which contains the string before the match.

- `\+` corresponds to `$+`, which contains the last capture group.

See `Regexp` for details.

Note that `\\` is interpreted as an escape, i.e., a single backslash.

Note also that a string literal consumes backslashes. See String Literals for details about string literals.

A back-reference is typically preceded by an additional backslash. For example, if you want to write a back-reference `\&` in `replacement` with a double-quoted string literal, you need to write `"..\\&.."`.

If you want to write a non-back-reference string `\&` in `replacement`, you need to first escape the backslash to prevent this method from interpreting it as a back-reference, and then you need to escape the backslashes again to prevent a string literal from consuming them: `"..\\\\&.."`.

You may want to use the block form to avoid excessive backslashes.

Hash `replacement`

If the argument `replacement` is a hash, and `pattern` matches one of its keys, the replacing string is the value for that key:

    h = {'foo' => 'bar', 'baz' => 'bat'}
    'food'.sub('foo', h) # => "bard"

Note that a symbol key does not match:

    h = {foo: 'bar', baz: 'bat'}
    'food'.sub('foo', h) # => "d"

Block

In the block form, the current match string is passed to the block; the block’s return value becomes the replacing string:

    s = '@'
    '1234'.gsub(/\d/) { |match| s.succ! } # => "ABCD"

Special match variables such as `$1`, `$2`, `$``, `$&`, and `$'` are set appropriately.

## Whitespace in Strings¶ ↑

In the class `String`, whitespace is defined as a contiguous sequence of characters consisting of any mixture of the following:

- NL (null): `"\x00"`, `"\u0000"`.

- HT (horizontal tab): `"\x09"`, `"\t"`.

- LF (line feed): `"\x0a"`, `"\n"`.

- VT (vertical tab): `"\x0b"`, `"\v"`.

- FF (form feed): `"\x0c"`, `"\f"`.

- CR (carriage return): `"\x0d"`, `"\r"`.

- SP (space): `"\x20"`, `" "`.

Whitespace is relevant for the following methods:

- `lstrip`, `lstrip!`: Strip leading whitespace.

- `rstrip`, `rstrip!`: Strip trailing whitespace.

- `strip`, `strip!`: Strip leading and trailing whitespace.

## `String` Slices¶ ↑

A slice of a string is a substring selected by certain criteria.

These instance methods utilize slicing:

- `String#[]` (aliased as `String#slice`): Returns a slice copied from `self`.

- `String#[]=`: Mutates `self` with the slice replaced.

- `String#slice!`: Mutates `self` with the slice removed and returns the removed slice.

Each of the above methods takes arguments that determine the slice to be copied or replaced.

The arguments have several forms. For a string `string`, the forms are:

- `string[index]`

- `string[start, length]`

- `string[range]`

- `string[regexp, capture = 0]`

- `string[substring]`

`string[index]`

When a non-negative integer argument `index` is given, the slice is the 1-character substring found in `self` at character offset `index`:

    'bar'[0]      # => "b"
    'bar'[2]      # => "r"
    'bar'[20]     # => nil
    'тест'[2]     # => "с"
    'こんにちは'[4] # => "は"

When a negative integer `index` is given, the slice begins at the offset given by counting backward from the end of `self`:

    'bar'[-3]      # => "b"
    'bar'[-1]      # => "r"
    'bar'[-20]     # => nil

`string[start, length]`

When non-negative integer arguments `start` and `length` are given, the slice begins at character offset `start`, if it exists, and continues for `length` characters, if available:

    'foo'[0, 2]      # => "fo"
    'тест'[1, 2]     # => "ес"
    'こんにちは'[2, 2] # => "にち"
    # Zero length.
    'foo'[2, 0]      # => ""
    # Length not entirely available.
    'foo'[1, 200]    # => "oo"
    # Start out of range.
    'foo'[4, 2]      # => nil

Special case: if `start` equals the length of `self`, the slice is a new empty string:

    'foo'[3, 2]    # => ""
    'foo'[3, 200]  # => ""

When a negative `start` and non-negative `length` are given, the slice begins by counting backward from the end of `self`, and continues for `length` characters, if available:

    'foo'[-2, 2]     # => "oo"
    'foo'[-2, 200]   # => "oo"
    # Start out of range.
    'foo'[-4, 2]     # => nil

When a negative `length` is given, there is no slice:

    'foo'[1, -1]   # => nil
    'foo'[-2, -1]  # => nil

`string[range]`

When a `Range` argument `range` is given, it creates a substring of `string` using the indices in `range`. The slice is then determined as above:

    'foo'[0..1]     # => "fo"
    'foo'[0, 2]     # => "fo"

    'foo'[2...2]    # => ""
    'foo'[2, 0]     # => ""

    'foo'[1..200]   # => "oo"
    'foo'[1, 200]   # => "oo"

    'foo'[4..5]     # => nil
    'foo'[4, 2]     # => nil

    'foo'[-4..-3]   # => nil
    'foo'[-4, 2]    # => nil

    'foo'[3..4]     # => ""
    'foo'[3, 2]     # => ""

    'foo'[-2..-1]   # => "oo"
    'foo'[-2, 2]    # => "oo"

    'foo'[-2..197]  # => "oo"
    'foo'[-2, 200]  # => "oo"

`string[regexp, capture = 0]`

When the `Regexp` argument `regexp` is given, and the `capture` argument is `0`, the slice is the first matching substring found in `self`:

    'foo'[/o/]                # => "o"
    'foo'[/x/]                # => nil
    s = 'hello there'
    s[/[aeiou](.)\1/]        # => "ell"
    s[/[aeiou](.)\1/, 0]     # => "ell"

If the argument `capture` is provided and not `0`, it should be either a capture group index (integer) or a capture group name (`String` or `Symbol`); the slice is the specified capture (see Groups at `Regexp` and Captures):

    s = 'hello there'
    s[/[aeiou](.)\1/, 1] # => "l"
    s[/(?<vowel>[aeiou])(?<non_vowel>[^aeiou])/, "non_vowel"] # => "l"
    s[/(?<vowel>[aeiou])(?<non_vowel>[^aeiou])/, :vowel]      # => "e"

If an invalid capture group index is given, there is no slice. If an invalid capture group name is given, `IndexError` is raised.

`string[substring]`

When the single `String` argument `substring` is given, it returns the substring from `self` if found, otherwise `nil`:

    'foo'['oo'] # => "oo"
    'foo'['xx'] # => nil

## What’s Here¶ ↑

First, what’s elsewhere. Class `String`:

- Inherits from the Object class.

- Includes the Comparable module.

Here, class `String` provides methods that are useful for:

- Creating a String

- Frozen/Unfrozen Strings

- Querying

- Comparing

- Modifying a String

- Converting to New String

- Converting to Non-String

- Iterating

### Methods for Creating a `String`¶ ↑

- `::new`: Returns a new string.

- `::try_convert`: Returns a new string created from a given object.

### Methods for a Frozen/Unfrozen `String`¶ ↑

- `+@`: Returns a string that is not frozen: `self` if not frozen; `self.dup` otherwise.

- `-@` (aliased as `dedup`): Returns a string that is frozen: `self` if already frozen; `self.freeze` otherwise.

- `freeze`: Freezes `self` if not already frozen; returns `self`.

### Methods for Querying¶ ↑

Counts

- `length` (aliased as `size`): Returns the count of characters (not bytes).

- `empty?`: Returns `true` if `self.length` is zero; `false` otherwise.

- `bytesize`: Returns the count of bytes.

- `count`: Returns the count of substrings matching given strings.

Substrings

- `=~`: Returns the index of the first substring that matches a given `Regexp` or other object; returns `nil` if no match is found.

- `index`: Returns the index of the first occurrence of a given substring; returns `nil` if none found.

- `rindex`: Returns the index of the last occurrence of a given substring; returns `nil` if none found.

- `include?`: Returns `true` if the string contains a given substring; `false` otherwise.

- `match`: Returns a `MatchData` object if the string matches a given `Regexp`; `nil` otherwise.

- `match?`: Returns `true` if the string matches a given `Regexp`; `false` otherwise.

- `start_with?`: Returns `true` if the string begins with any of the given substrings.

- `end_with?`: Returns `true` if the string ends with any of the given substrings.

Encodings

- `encoding`: Returns the `Encoding` object that represents the encoding of the string.

- `unicode_normalized?`: Returns `true` if the string is in Unicode normalized form; `false` otherwise.

- `valid_encoding?`: Returns `true` if the string contains only characters that are valid for its encoding.

- `ascii_only?`: Returns `true` if the string has only ASCII characters; `false` otherwise.

Other

- `sum`: Returns a basic checksum for the string: the sum of each byte.

- `hash`: Returns the integer hash code.

### Methods for Comparing¶ ↑

- `==` (aliased as `===`): Returns `true` if a given other string has the same content as `self`.

- `eql?`: Returns `true` if the content is the same as the given other string.

- `<=>`: Returns -1, 0, or 1 as a given other string is smaller than, equal to, or larger than `self`.

- `casecmp`: Ignoring case, returns -1, 0, or 1 as a given other string is smaller than, equal to, or larger than `self`.

- `casecmp?`: Returns `true` if the string is equal to a given string after Unicode case folding; `false` otherwise.

### Methods for Modifying a `String`¶ ↑

Each of these methods modifies `self`.

Insertion

- `insert`: Returns `self` with a given string inserted at a specified offset.

- `<<`: Returns `self` concatenated with a given string or integer.

- `append_as_bytes`: Returns `self` concatenated with strings without performing any encoding validation or conversion.

Substitution

- `sub!`: Replaces the first substring that matches a given pattern with a given replacement string; returns `self` if any changes, `nil` otherwise.

- `gsub!`: Replaces each substring that matches a given pattern with a given replacement string; returns `self` if any changes, `nil` otherwise.

- `succ!` (aliased as `next!`): Returns `self` modified to become its own successor.

- `initialize_copy` (aliased as `replace`): Returns `self` with its entire content replaced by a given string.

- `reverse!`: Returns `self` with its characters in reverse order.

- `setbyte`: Sets the byte at a given integer offset to a given value; returns the argument.

- `tr!`: Replaces specified characters in `self` with specified replacement characters; returns `self` if any changes, `nil` otherwise.

- `tr_s!`: Replaces specified characters in `self` with specified replacement characters, removing duplicates from the substrings that were modified; returns `self` if any changes, `nil` otherwise.

Casing

- `capitalize!`: Upcases the initial character and downcases all others; returns `self` if any changes, `nil` otherwise.

- `downcase!`: Downcases all characters; returns `self` if any changes, `nil` otherwise.

- `upcase!`: Upcases all characters; returns `self` if any changes, `nil` otherwise.

- `swapcase!`: Upcases each downcase character and downcases each upcase character; returns `self` if any changes, `nil` otherwise.

Encoding

- `encode!`: Returns `self` with all characters transcoded from one encoding to another.

- `unicode_normalize!`: Unicode-normalizes `self`; returns `self`.

- `scrub!`: Replaces each invalid byte with a given character; returns `self`.

- `force_encoding`: Changes the encoding to a given encoding; returns `self`.

Deletion

- `clear`: Removes all content, so that `self` is empty; returns `self`.

- `slice!`, `[]=`: Removes a substring determined by a given index, start/length, range, regexp, or substring.

- `squeeze!`: Removes contiguous duplicate characters; returns `self`.

- `delete!`: Removes characters as determined by the intersection of substring arguments.

- `lstrip!`: Removes leading whitespace; returns `self` if any changes, `nil` otherwise.

- `rstrip!`: Removes trailing whitespace; returns `self` if any changes, `nil` otherwise.

- `strip!`: Removes leading and trailing whitespace; returns `self` if any changes, `nil` otherwise.

- `chomp!`: Removes the trailing record separator, if found; returns `self` if any changes, `nil` otherwise.

- `chop!`: Removes trailing newline characters if found; otherwise removes the last character; returns `self` if any changes, `nil` otherwise.

### Methods for Converting to New `String`¶ ↑

Each of these methods returns a new `String` based on `self`, often just a modified copy of `self`.

Extension

- `*`: Returns the concatenation of multiple copies of `self`.

- `+`: Returns the concatenation of `self` and a given other string.

- `center`: Returns a copy of `self` centered between pad substrings.

- `concat`: Returns the concatenation of `self` with given other strings.

- `prepend`: Returns the concatenation of a given other string with `self`.

- `ljust`: Returns a copy of `self` of a given length, right-padded with a given other string.

- `rjust`: Returns a copy of `self` of a given length, left-padded with a given other string.

Encoding

- `b`: Returns a copy of `self` with ASCII-8BIT encoding.

- `scrub`: Returns a copy of `self` with each invalid byte replaced with a given character.

- `unicode_normalize`: Returns a copy of `self` with each character Unicode-normalized.

- `encode`: Returns a copy of `self` with all characters transcoded from one encoding to another.

Substitution

- `dump`: Returns a copy of `self` with all non-printing characters replaced by xHH notation and all special characters escaped.

- `undump`: Returns a copy of `self` with all `\xNN` notations replaced by `\uNNNN` notations and all escaped characters unescaped.

- `sub`: Returns a copy of `self` with the first substring matching a given pattern replaced with a given replacement string.

- `gsub`: Returns a copy of `self` with each substring that matches a given pattern replaced with a given replacement string.

- `succ` (aliased as `next`): Returns the string that is the successor to `self`.

- `reverse`: Returns a copy of `self` with its characters in reverse order.

- `tr`: Returns a copy of `self` with specified characters replaced with specified replacement characters.

- `tr_s`: Returns a copy of `self` with specified characters replaced with specified replacement characters, removing duplicates from the substrings that were modified.

- `%`: Returns the string resulting from formatting a given object into `self`.

Casing

- `capitalize`: Returns a copy of `self` with the first character upcased and all other characters downcased.

- `downcase`: Returns a copy of `self` with all characters downcased.

- `upcase`: Returns a copy of `self` with all characters upcased.

- `swapcase`: Returns a copy of `self` with all upcase characters downcased and all downcase characters upcased.

Deletion

- `delete`: Returns a copy of `self` with characters removed.

- `delete_prefix`: Returns a copy of `self` with a given prefix removed.

- `delete_suffix`: Returns a copy of `self` with a given suffix removed.

- `lstrip`: Returns a copy of `self` with leading whitespace removed.

- `rstrip`: Returns a copy of `self` with trailing whitespace removed.

- `strip`: Returns a copy of `self` with leading and trailing whitespace removed.

- `chomp`: Returns a copy of `self` with a trailing record separator removed, if found.

- `chop`: Returns a copy of `self` with trailing newline characters or the last character removed.

- `squeeze`: Returns a copy of `self` with contiguous duplicate characters removed.

- `[]` (aliased as `slice`): Returns a substring determined by a given index, start/length, range, regexp, or string.

- `byteslice`: Returns a substring determined by a given index, start/length, or range.

- `chr`: Returns the first character.

Duplication

- `to_s` (aliased as `to_str`): If `self` is a subclass of `String`, returns `self` copied into a `String`; otherwise, returns `self`.

### Methods for Converting to Non-`String`¶ ↑

Each of these methods converts the contents of `self` to a non-`String`.

Characters, Bytes, and Clusters

- `bytes`: Returns an array of the bytes in `self`.

- `chars`: Returns an array of the characters in `self`.

- `codepoints`: Returns an array of the integer ordinals in `self`.

- `getbyte`: Returns the integer byte at the given index in `self`.

- `grapheme_clusters`: Returns an array of the grapheme clusters in `self`.

Splitting

- `lines`: Returns an array of the lines in `self`, as determined by a given record separator.

- `partition`: Returns a 3-element array determined by the first substring that matches a given substring or regexp.

- `rpartition`: Returns a 3-element array determined by the last substring that matches a given substring or regexp.

- `split`: Returns an array of substrings determined by a given delimiter – regexp or string – or, if a block is given, passes those substrings to the block.

Matching

- `scan`: Returns an array of substrings matching a given regexp or string, or, if a block is given, passes each matching substring to the block.

- `unpack`: Returns an array of substrings extracted from `self` according to a given format.

- `unpack1`: Returns the first substring extracted from `self` according to a given format.

Numerics

- `hex`: Returns the integer value of the leading characters, interpreted as hexadecimal digits.

- `oct`: Returns the integer value of the leading characters, interpreted as octal digits.

- `ord`: Returns the integer ordinal of the first character in `self`.

- `to_i`: Returns the integer value of leading characters, interpreted as an integer.

- `to_f`: Returns the floating-point value of leading characters, interpreted as a floating-point number.

Strings and Symbols

- `inspect`: Returns a copy of `self`, enclosed in double quotes, with special characters escaped.

- `intern` (aliased as `to_sym`): Returns the symbol corresponding to `self`.

### Methods for Iterating¶ ↑

- `each_byte`: Calls the given block with each successive byte in `self`.

- `each_char`: Calls the given block with each successive character in `self`.

- `each_codepoint`: Calls the given block with each successive integer codepoint in `self`.

- `each_grapheme_cluster`: Calls the given block with each successive grapheme cluster in `self`.

- `each_line`: Calls the given block with each successive line in `self`, as determined by a given record separator.

- `upto`: Calls the given block with each string value returned by successive calls to `succ`.

### Public Class Methods

new(string = '', **opts) → new_string
Source

    static VALUE
    rb_str_init(int argc, VALUE *argv, VALUE str)
    {
        static ID keyword_ids[2];
        VALUE orig, opt, venc, vcapa;
        VALUE kwargs[2];
        rb_encoding *enc = 0;
        int n;

        if (!keyword_ids[0]) {
            keyword_ids[0] = rb_id_encoding();
            CONST_ID(keyword_ids[1], "capacity");
        }

        n = rb_scan_args(argc, argv, "01:", &orig, &opt);
        if (!NIL_P(opt)) {
            rb_get_kwargs(opt, keyword_ids, 0, 2, kwargs);
            venc = kwargs[0];
            vcapa = kwargs[1];
            if (!UNDEF_P(venc) && !NIL_P(venc)) {
                enc = rb_to_encoding(venc);
            }
            if (!UNDEF_P(vcapa) && !NIL_P(vcapa)) {
                long capa = NUM2LONG(vcapa);
                long len = 0;
                int termlen = enc ? rb_enc_mbminlen(enc) : 1;

                if (capa < STR_BUF_MIN_SIZE) {
                    capa = STR_BUF_MIN_SIZE;
                }
                if (n == 1) {
                    StringValue(orig);
                    len = RSTRING_LEN(orig);
                    if (capa < len) {
                        capa = len;
                    }
                    if (orig == str) n = 0;
                }
                str_modifiable(str);
                if (STR_EMBED_P(str) || FL_TEST(str, STR_SHARED|STR_NOFREE)) {
                    /* make noembed always */
                    const size_t size = (size_t)capa + termlen;
                    const char *const old_ptr = RSTRING_PTR(str);
                    const size_t osize = RSTRING_LEN(str) + TERM_LEN(str);
                    char *new_ptr = ALLOC_N(char, size);
                    if (STR_EMBED_P(str)) RUBY_ASSERT((long)osize <= str_embed_capa(str));
                    memcpy(new_ptr, old_ptr, osize < size ? osize : size);
                    FL_UNSET_RAW(str, STR_SHARED|STR_NOFREE);
                    RSTRING(str)->as.heap.ptr = new_ptr;
                }
                else if (STR_HEAP_SIZE(str) != (size_t)capa + termlen) {
                    SIZED_REALLOC_N(RSTRING(str)->as.heap.ptr, char,
                            (size_t)capa + termlen, STR_HEAP_SIZE(str));
                }
                STR_SET_LEN(str, len);
                TERM_FILL(&RSTRING(str)->as.heap.ptr[len], termlen);
                if (n == 1) {
                    memcpy(RSTRING(str)->as.heap.ptr, RSTRING_PTR(orig), len);
                    rb_enc_cr_str_exact_copy(str, orig);
                }
                FL_SET(str, STR_NOEMBED);
                RSTRING(str)->as.heap.aux.capa = capa;
            }
            else if (n == 1) {
                rb_str_replace(str, orig);
            }
            if (enc) {
                rb_enc_associate(str, enc);
                ENC_CODERANGE_CLEAR(str);
            }
        }
        else if (n == 1) {
            rb_str_replace(str, orig);
        }
        return str;
    }

Returns a new String that is a copy of `string`.

With no arguments, returns the empty string with the `Encoding` `ASCII-8BIT`:

    s = String.new
    s # => ""
    s.encoding # => #<Encoding:ASCII-8BIT>

With optional argument `string` and no keyword arguments, returns a copy of `string` with the same encoding:

    String.new('foo')               # => "foo"
    String.new('тест')              # => "тест"
    String.new('こんにちは')          # => "こんにちは"

(Unlike String.new, a string literal like `''` or a here document literal always has script encoding.)

With optional keyword argument `encoding`, returns a copy of `string` with the specified encoding; the `encoding` may be an `Encoding` object, an encoding name, or an encoding name alias:

    String.new('foo', encoding: Encoding::US_ASCII).encoding # => #<Encoding:US-ASCII>
    String.new('foo', encoding: 'US-ASCII').encoding         # => #<Encoding:US-ASCII>
    String.new('foo', encoding: 'ASCII').encoding            # => #<Encoding:US-ASCII>

The given encoding need not be valid for the string’s content, and that validity is not checked:

    s = String.new('こんにちは', encoding: 'ascii')
    s.valid_encoding? # => false

But the given `encoding` itself is checked:

    String.new('foo', encoding: 'bar') # Raises ArgumentError.

With optional keyword argument `capacity`, returns a copy of `string` (or an empty string, if `string` is not given); the given `capacity` is advisory only, and may or may not set the size of the internal buffer, which may in turn affect performance:

    String.new(capacity: 1)
    String.new('foo', capacity: 4096)

Note that Ruby strings are null-terminated internally, so the internal buffer size will be one or more bytes larger than the requested capacity depending on the encoding.

The `string`, `encoding`, and `capacity` arguments may all be used together:

    String.new('hello', encoding: 'UTF-8', capacity: 25)

try_convert(object) → object, new_string, or nil
Source

    static VALUE
    rb_str_s_try_convert(VALUE dummy, VALUE str)
    {
        return rb_check_string_type(str);
    }

If `object` is a `String` object, returns `object`.

Otherwise if `object` responds to `:to_str`, calls `object.to_str` and returns the result.

Returns `nil` if `object` does not respond to `:to_str`.

Raises an exception unless `object.to_str` returns a `String` object.

### Public Instance Methods

string % object → new_string
Source

    static VALUE
    rb_str_format_m(VALUE str, VALUE arg)
    {
        VALUE tmp = rb_check_array_type(arg);

        if (!NIL_P(tmp)) {
            return rb_str_format(RARRAY_LENINT(tmp), RARRAY_CONST_PTR(tmp), str);
        }
        return rb_str_format(1, &arg, str);
    }

Returns the result of formatting `object` into the format specification `self` (see `Kernel#sprintf` for formatting details):

    "%05d" % 123 # => "00123"

If `self` contains multiple substitutions, `object` must be an `Array` or `Hash` containing the values to be substituted:

    "%-5s: %016x" % [ "ID", self.object_id ] # => "ID   : 00002b054ec93168"
    "foo = %{foo}" % {foo: 'bar'} # => "foo = bar"
    "foo = %{foo}, baz = %{baz}" % {foo: 'bar', baz: 'bat'} # => "foo = bar, baz = bat"

string * integer → new_string
Source

    VALUE
    rb_str_times(VALUE str, VALUE times)
    {
        VALUE str2;
        long n, len;
        char *ptr2;
        int termlen;

        if (times == INT2FIX(1)) {
            return str_duplicate(rb_cString, str);
        }
        if (times == INT2FIX(0)) {
            str2 = str_alloc_embed(rb_cString, 0);
            rb_enc_copy(str2, str);
            return str2;
        }
        len = NUM2LONG(times);
        if (len < 0) {
            rb_raise(rb_eArgError, "negative argument");
        }
        if (RSTRING_LEN(str) == 1 && RSTRING_PTR(str)[0] == 0) {
            if (STR_EMBEDDABLE_P(len, 1)) {
                str2 = str_alloc_embed(rb_cString, len + 1);
                memset(RSTRING_PTR(str2), 0, len + 1);
            }
            else {
                str2 = str_alloc_heap(rb_cString);
                RSTRING(str2)->as.heap.aux.capa = len;
                RSTRING(str2)->as.heap.ptr = ZALLOC_N(char, (size_t)len + 1);
            }
            STR_SET_LEN(str2, len);
            rb_enc_copy(str2, str);
            return str2;
        }
        if (len && LONG_MAX/len <  RSTRING_LEN(str)) {
            rb_raise(rb_eArgError, "argument too big");
        }

        len *= RSTRING_LEN(str);
        termlen = TERM_LEN(str);
        str2 = str_enc_new(rb_cString, 0, len, STR_ENC_GET(str));
        ptr2 = RSTRING_PTR(str2);
        if (len) {
            n = RSTRING_LEN(str);
            memcpy(ptr2, RSTRING_PTR(str), n);
            while (n <= len/2) {
                memcpy(ptr2 + n, ptr2, n);
                n *= 2;
            }
            memcpy(ptr2 + n, ptr2, len-n);
        }
        STR_SET_LEN(str2, len);
        TERM_FILL(&ptr2[len], termlen);
        rb_enc_cr_str_copy_for_substr(str2, str);

        return str2;
    }

Returns a new `String` containing `integer` copies of `self`:

    "Ho! " * 3 # => "Ho! Ho! Ho! "
    "Ho! " * 0 # => ""

string + other_string → new_string
Source

    VALUE
    rb_str_plus(VALUE str1, VALUE str2)
    {
        VALUE str3;
        rb_encoding *enc;
        char *ptr1, *ptr2, *ptr3;
        long len1, len2;
        int termlen;

        StringValue(str2);
        enc = rb_enc_check_str(str1, str2);
        RSTRING_GETMEM(str1, ptr1, len1);
        RSTRING_GETMEM(str2, ptr2, len2);
        termlen = rb_enc_mbminlen(enc);
        if (len1 > LONG_MAX - len2) {
            rb_raise(rb_eArgError, "string size too big");
        }
        str3 = str_enc_new(rb_cString, 0, len1+len2, enc);
        ptr3 = RSTRING_PTR(str3);
        memcpy(ptr3, ptr1, len1);
        memcpy(ptr3+len1, ptr2, len2);
        TERM_FILL(&ptr3[len1+len2], termlen);

        ENCODING_CODERANGE_SET(str3, rb_enc_to_index(enc),
                               ENC_CODERANGE_AND(ENC_CODERANGE(str1), ENC_CODERANGE(str2)));
        RB_GC_GUARD(str1);
        RB_GC_GUARD(str2);
        return str3;
    }

Returns a new `String` containing `other_string` concatenated to `self`:

    "Hello from " + self.to_s # => "Hello from main"

+string → new_string or self
Source

    static VALUE
    str_uplus(VALUE str)
    {
        if (OBJ_FROZEN(str) || CHILLED_STRING_P(str)) {
            return rb_str_dup(str);
        }
        else {
            return str;
        }
    }

Returns `self` if `self` is not frozen and can be mutated without warning issuance.

Otherwise returns `self.dup`, which is not frozen.

-string → frozen_string
Source

    static VALUE
    str_uminus(VALUE str)
    {
        if (!BARE_STRING_P(str) && !rb_obj_frozen_p(str)) {
            str = rb_str_dup(str);
        }
        return rb_fstring(str);
    }

Returns a frozen, possibly pre-existing copy of the string.

The returned `String` will be deduplicated as long as it does not have any instance variables set on it and is not a `String` subclass.

Note that `-string` variant is more convenient for defining constants:

    FILENAME = -'config/database.yml'

while `dedup` is better suitable for using the method in chains of calculations:

    @url_list.concat(urls.map(&:dedup))

Also aliased as: dedup
string << object → string
Source

    VALUE
    rb_str_concat(VALUE str1, VALUE str2)
    {
        unsigned int code;
        rb_encoding *enc = STR_ENC_GET(str1);
        int encidx;

        if (RB_INTEGER_TYPE_P(str2)) {
            if (rb_num_to_uint(str2, &code) == 0) {
            }
            else if (FIXNUM_P(str2)) {
                rb_raise(rb_eRangeError, "%ld out of char range", FIX2LONG(str2));
            }
            else {
                rb_raise(rb_eRangeError, "bignum out of char range");
            }
        }
        else {
            return rb_str_append(str1, str2);
        }

        encidx = rb_ascii8bit_appendable_encoding_index(enc, code);

        if (encidx >= 0) {
            rb_str_buf_cat_byte(str1, (unsigned char)code);
        }
        else {
            long pos = RSTRING_LEN(str1);
            int cr = ENC_CODERANGE(str1);
            int len;
            char *buf;

            switch (len = rb_enc_codelen(code, enc)) {
              case ONIGERR_INVALID_CODE_POINT_VALUE:
                rb_raise(rb_eRangeError, "invalid codepoint 0x%X in %s", code, rb_enc_name(enc));
                break;
              case ONIGERR_TOO_BIG_WIDE_CHAR_VALUE:
              case 0:
                rb_raise(rb_eRangeError, "%u out of char range", code);
                break;
            }
            buf = ALLOCA_N(char, len + 1);
            rb_enc_mbcput(code, buf, enc);
            if (rb_enc_precise_mbclen(buf, buf + len + 1, enc) != len) {
                rb_raise(rb_eRangeError, "invalid codepoint 0x%X in %s", code, rb_enc_name(enc));
            }
            rb_str_resize(str1, pos+len);
            memcpy(RSTRING_PTR(str1) + pos, buf, len);
            if (cr == ENC_CODERANGE_7BIT && code > 127) {
                cr = ENC_CODERANGE_VALID;
            }
            else if (cr == ENC_CODERANGE_BROKEN) {
                cr = ENC_CODERANGE_UNKNOWN;
            }
            ENC_CODERANGE_SET(str1, cr);
        }
        return str1;
    }

Concatenates `object` to `self` and returns `self`:

    s = 'foo'
    s << 'bar' # => "foobar"
    s          # => "foobar"

If `object` is an `Integer`, the value is considered a codepoint and converted to a character before concatenation:

    s = 'foo'
    s << 33 # => "foo!"

If that codepoint is not representable in the encoding of string, `RangeError` is raised.

    s = 'foo'
    s.encoding              # => <Encoding:UTF-8>
    s << 0x00110000         # 1114112 out of char range (RangeError)
    s = 'foo'.encode('EUC-JP')
    s << 0x00800080         # invalid codepoint 0x800080 in EUC-JP (RangeError)

If the encoding is US-ASCII and the codepoint is 0..0xff, string is automatically promoted to ASCII-8BIT.

    s = 'foo'.encode('US-ASCII')
    s << 0xff
    s.encoding              # => #<Encoding:BINARY (ASCII-8BIT)>

Related: `String#concat`, which takes multiple arguments.

string <=> other_string → -1, 0, 1, or nil
Source

    static VALUE
    rb_str_cmp_m(VALUE str1, VALUE str2)
    {
        int result;
        VALUE s = rb_check_string_type(str2);
        if (NIL_P(s)) {
            return rb_invcmp(str1, str2);
        }
        result = rb_str_cmp(str1, s);
        return INT2FIX(result);
    }

Compares `self` and `other_string`, returning:

- -1 if `other_string` is larger.

- 0 if the two are equal.

- 1 if `other_string` is smaller.

- `nil` if the two are incomparable.

Examples:

    'foo' <=> 'foo' # => 0
    'foo' <=> 'food' # => -1
    'food' <=> 'foo' # => 1
    'FOO' <=> 'foo' # => -1
    'foo' <=> 'FOO' # => 1
    'foo' <=> 1 # => nil

string == object → true or false
Source

    VALUE
    rb_str_equal(VALUE str1, VALUE str2)
    {
        if (str1 == str2) return Qtrue;
        if (!RB_TYPE_P(str2, T_STRING)) {
            if (!rb_respond_to(str2, idTo_str)) {
                return Qfalse;
            }
            return rb_equal(str2, str1);
        }
        return rb_str_eql_internal(str1, str2);
    }

Returns `true` if `object` has the same length and content; as `self`; `false` otherwise:

    s = 'foo'
    s == 'foo' # => true
    s == 'food' # => false
    s == 'FOO' # => false

Returns `false` if the two strings’ encodings are not compatible:

    "\u{e4 f6 fc}".encode("ISO-8859-1") == ("\u{c4 d6 dc}") # => false

If `object` is not an instance of `String` but responds to `to_str`, then the two strings are compared using `object.==`.

Also aliased as: ===
string === object → true or false

Returns `true` if `object` has the same length and content; as `self`; `false` otherwise:

    s = 'foo'
    s == 'foo' # => true
    s == 'food' # => false
    s == 'FOO' # => false

Returns `false` if the two strings’ encodings are not compatible:

    "\u{e4 f6 fc}".encode("ISO-8859-1") == ("\u{c4 d6 dc}") # => false

If `object` is not an instance of `String` but responds to `to_str`, then the two strings are compared using `object.==`.

Alias for: ==
string =~ regexp → integer or nil
string =~ object → integer or nil
Source

    static VALUE
    rb_str_match(VALUE x, VALUE y)
    {
        switch (OBJ_BUILTIN_TYPE(y)) {
          case T_STRING:
            rb_raise(rb_eTypeError, "type mismatch: String given");

          case T_REGEXP:
            return rb_reg_match(y, x);

          default:
            return rb_funcall(y, idEqTilde, 1, x);
        }
    }

Returns the `Integer` index of the first substring that matches the given `regexp`, or `nil` if no match found:

    'foo' =~ /f/ # => 0
    'foo' =~ /o/ # => 1
    'foo' =~ /x/ # => nil

Note: also updates Global Variables at `Regexp`.

If the given `object` is not a `Regexp`, returns the value returned by `object =~ self`.

Note that `string =~ regexp` is different from `regexp =~ string` (see `Regexp#=~`):

    number= nil
    "no. 9" =~ /(?<number>\d+)/
    number # => nil (not assigned)
    /(?<number>\d+)/ =~ "no. 9"
    number #=> "9"

string[index] → new_string or nil
string[start, length] → new_string or nil
string[range] → new_string or nil
string[regexp, capture = 0] → new_string or nil
string[substring] → new_string or nil
Source

    static VALUE
    rb_str_aref_m(int argc, VALUE *argv, VALUE str)
    {
        if (argc == 2) {
            if (RB_TYPE_P(argv[0], T_REGEXP)) {
                return rb_str_subpat(str, argv[0], argv[1]);
            }
            else {
                return rb_str_substr_two_fixnums(str, argv[0], argv[1], TRUE);
            }
        }
        rb_check_arity(argc, 1, 2);
        return rb_str_aref(str, argv[0]);
    }

Returns the substring of `self` specified by the arguments. See examples at String Slices.

Also aliased as: slice
string[index] = new_string
string[start, length] = new_string
string[range] = new_string
string[regexp, capture = 0] = new_string
string[substring] = new_string
Source

    static VALUE
    rb_str_aset_m(int argc, VALUE *argv, VALUE str)
    {
        if (argc == 3) {
            if (RB_TYPE_P(argv[0], T_REGEXP)) {
                rb_str_subpat_set(str, argv[0], argv[1], argv[2]);
            }
            else {
                rb_str_update(str, NUM2LONG(argv[0]), NUM2LONG(argv[1]), argv[2]);
            }
            return argv[2];
        }
        rb_check_arity(argc, 2, 3);
        return rb_str_aset(str, argv[0], argv[1]);
    }

Replaces all, some, or none of the contents of `self`; returns `new_string`. See String Slices.

A few examples:

    s = 'foo'
    s[2] = 'rtune'     # => "rtune"
    s                  # => "fortune"
    s[1, 5] = 'init'   # => "init"
    s                  # => "finite"
    s[3..4] = 'al'     # => "al"
    s                  # => "finale"
    s[/e$/] = 'ly'     # => "ly"
    s                  # => "finally"
    s['lly'] = 'ncial' # => "ncial"
    s                  # => "financial"

append_as_bytes(*objects) → string
Source

    VALUE
    rb_str_append_as_bytes(int argc, VALUE *argv, VALUE str)
    {
        long needed_capacity = 0;
        volatile VALUE t0;
        enum ruby_value_type *types = ALLOCV_N(enum ruby_value_type, t0, argc);

        for (int index = 0; index < argc; index++) {
            VALUE obj = argv[index];
            enum ruby_value_type type = types[index] = rb_type(obj);
            switch (type) {
              case T_FIXNUM:
              case T_BIGNUM:
                needed_capacity++;
                break;
              case T_STRING:
                needed_capacity += RSTRING_LEN(obj);
                break;
              default:
                rb_raise(
                    rb_eTypeError,
                    "wrong argument type %"PRIsVALUE" (expected String or Integer)",
                    rb_obj_class(obj)
                );
                break;
            }
        }

        str_ensure_available_capa(str, needed_capacity);
        char *sptr = RSTRING_END(str);

        for (int index = 0; index < argc; index++) {
            VALUE obj = argv[index];
            enum ruby_value_type type = types[index];
            switch (type) {
              case T_FIXNUM:
              case T_BIGNUM: {
                argv[index] = obj = rb_int_and(obj, INT2FIX(0xff));
                char byte = (char)(NUM2INT(obj) & 0xFF);
                *sptr = byte;
                sptr++;
                break;
              }
              case T_STRING: {
                const char *ptr;
                long len;
                RSTRING_GETMEM(obj, ptr, len);
                memcpy(sptr, ptr, len);
                sptr += len;
                break;
              }
              default:
                rb_bug("append_as_bytes arguments should have been validated");
            }
        }

        STR_SET_LEN(str, RSTRING_LEN(str) + needed_capacity);
        TERM_FILL(sptr, TERM_LEN(str)); /* sentinel */

        int cr = ENC_CODERANGE(str);
        switch (cr) {
          case ENC_CODERANGE_7BIT: {
            for (int index = 0; index < argc; index++) {
                VALUE obj = argv[index];
                enum ruby_value_type type = types[index];
                switch (type) {
                  case T_FIXNUM:
                  case T_BIGNUM: {
                    if (!ISASCII(NUM2INT(obj))) {
                        goto clear_cr;
                    }
                    break;
                  }
                  case T_STRING: {
                    if (ENC_CODERANGE(obj) != ENC_CODERANGE_7BIT) {
                        goto clear_cr;
                    }
                    break;
                  }
                  default:
                    rb_bug("append_as_bytes arguments should have been validated");
                }
            }
            break;
          }
          case ENC_CODERANGE_VALID:
            if (ENCODING_GET_INLINED(str) == ENCINDEX_ASCII_8BIT) {
                goto keep_cr;
            }
            else {
                goto clear_cr;
            }
            break;
          default:
            goto clear_cr;
            break;
        }

        RB_GC_GUARD(t0);

      clear_cr:
        // If no fast path was hit, we clear the coderange.
        // append_as_bytes is predominently meant to be used in
        // buffering situation, hence it's likely the coderange
        // will never be scanned, so it's not worth spending time
        // precomputing the coderange except for simple and common
        // situations.
        ENC_CODERANGE_CLEAR(str);
      keep_cr:
        return str;
    }

Concatenates each object in `objects` into `self` without any encoding validation or conversion and returns `self`:

    s = 'foo'
    s.append_as_bytes(" \xE2\x82")  # => "foo \xE2\x82"
    s.valid_encoding?               # => false
    s.append_as_bytes("\xAC 12")
    s.valid_encoding?               # => true

For each given object `object` that is an `Integer`, the value is considered a Byte. If the `Integer` is bigger than one byte, only the lower byte is considered, similar to `String#setbyte`:

    s = ""
    s.append_as_bytes(0, 257)             # =>  "\u0000\u0001"

Related: `String#<<`, `String#concat`, which do an encoding aware concatenation.

ascii_only? → true or false
Source

    static VALUE
    rb_str_is_ascii_only_p(VALUE str)
    {
        int cr = rb_enc_str_coderange(str);

        return RBOOL(cr == ENC_CODERANGE_7BIT);
    }

Returns `true` if `self` contains only ASCII characters, `false` otherwise:

    'abc'.ascii_only?         # => true
    "abc\u{6666}".ascii_only? # => false

b → string
Source

    static VALUE
    rb_str_b(VALUE str)
    {
        VALUE str2;
        if (STR_EMBED_P(str)) {
            str2 = str_alloc_embed(rb_cString, RSTRING_LEN(str) + TERM_LEN(str));
        }
        else {
            str2 = str_alloc_heap(rb_cString);
        }
        str_replace_shared_without_enc(str2, str);

        if (rb_enc_asciicompat(STR_ENC_GET(str))) {
            // BINARY strings can never be broken; they're either 7-bit ASCII or VALID.
            // If we know the receiver's code range then we know the result's code range.
            int cr = ENC_CODERANGE(str);
            switch (cr) {
              case ENC_CODERANGE_7BIT:
                ENC_CODERANGE_SET(str2, ENC_CODERANGE_7BIT);
                break;
              case ENC_CODERANGE_BROKEN:
              case ENC_CODERANGE_VALID:
                ENC_CODERANGE_SET(str2, ENC_CODERANGE_VALID);
                break;
              default:
                ENC_CODERANGE_CLEAR(str2);
                break;
            }
        }

        return str2;
    }

Returns a copy of `self` that has ASCII-8BIT encoding; the underlying bytes are not modified:

    s = "\x99"
    s.encoding   # => #<Encoding:UTF-8>
    t = s.b      # => "\x99"
    t.encoding   # => #<Encoding:ASCII-8BIT>

    s = "\u4095" # => "䂕"
    s.encoding   # => #<Encoding:UTF-8>
    s.bytes      # => [228, 130, 149]
    t = s.b      # => "\xE4\x82\x95"
    t.encoding   # => #<Encoding:ASCII-8BIT>
    t.bytes      # => [228, 130, 149]

byteindex(substring, offset = 0) → integer or nil
byteindex(regexp, offset = 0) → integer or nil
Source

    static VALUE
    rb_str_byteindex_m(int argc, VALUE *argv, VALUE str)
    {
        VALUE sub;
        VALUE initpos;
        long pos;

        if (rb_scan_args(argc, argv, "11", &sub, &initpos) == 2) {
            long slen = RSTRING_LEN(str);
            pos = NUM2LONG(initpos);
            if (pos < 0 ? (pos += slen) < 0 : pos > slen) {
                if (RB_TYPE_P(sub, T_REGEXP)) {
                    rb_backref_set(Qnil);
                }
                return Qnil;
            }
        }
        else {
            pos = 0;
        }

        str_ensure_byte_pos(str, pos);

        if (RB_TYPE_P(sub, T_REGEXP)) {
            if (rb_reg_search(sub, str, pos, 0) >= 0) {
                VALUE match = rb_backref_get();
                struct re_registers *regs = RMATCH_REGS(match);
                pos = BEG(0);
                return LONG2NUM(pos);
            }
        }
        else {
            StringValue(sub);
            pos = rb_str_byteindex(str, sub, pos);
            if (pos >= 0) return LONG2NUM(pos);
        }
        return Qnil;
    }

Returns the `Integer` byte-based index of the first occurrence of the given `substring`, or `nil` if none found:

    'foo'.byteindex('f') # => 0
    'foo'.byteindex('o') # => 1
    'foo'.byteindex('oo') # => 1
    'foo'.byteindex('ooo') # => nil

Returns the `Integer` byte-based index of the first match for the given `Regexp` `regexp`, or `nil` if none found:

    'foo'.byteindex(/f/) # => 0
    'foo'.byteindex(/o/) # => 1
    'foo'.byteindex(/oo/) # => 1
    'foo'.byteindex(/ooo/) # => nil

`Integer` argument `offset`, if given, specifies the byte-based position in the string to begin the search:

    'foo'.byteindex('o', 1) # => 1
    'foo'.byteindex('o', 2) # => 2
    'foo'.byteindex('o', 3) # => nil

If `offset` is negative, counts backward from the end of `self`:

    'foo'.byteindex('o', -1) # => 2
    'foo'.byteindex('o', -2) # => 1
    'foo'.byteindex('o', -3) # => 1
    'foo'.byteindex('o', -4) # => nil

If `offset` does not land on character (codepoint) boundary, `IndexError` is raised.

Related: `String#index`, `String#byterindex`.

byterindex(substring, offset = self.bytesize) → integer or nil
byterindex(regexp, offset = self.bytesize) → integer or nil
Source

    static VALUE
    rb_str_byterindex_m(int argc, VALUE *argv, VALUE str)
    {
        VALUE sub;
        VALUE initpos;
        long pos, len = RSTRING_LEN(str);

        if (rb_scan_args(argc, argv, "11", &sub, &initpos) == 2) {
            pos = NUM2LONG(initpos);
            if (pos < 0 && (pos += len) < 0) {
                if (RB_TYPE_P(sub, T_REGEXP)) {
                    rb_backref_set(Qnil);
                }
                return Qnil;
            }
            if (pos > len) pos = len;
        }
        else {
            pos = len;
        }

        str_ensure_byte_pos(str, pos);

        if (RB_TYPE_P(sub, T_REGEXP)) {
            if (rb_reg_search(sub, str, pos, 1) >= 0) {
                VALUE match = rb_backref_get();
                struct re_registers *regs = RMATCH_REGS(match);
                pos = BEG(0);
                return LONG2NUM(pos);
            }
        }
        else {
            StringValue(sub);
            pos = rb_str_byterindex(str, sub, pos);
            if (pos >= 0) return LONG2NUM(pos);
        }
        return Qnil;
    }

Returns the `Integer` byte-based index of the last occurrence of the given `substring`, or `nil` if none found:

    'foo'.byterindex('f') # => 0
    'foo'.byterindex('o') # => 2
    'foo'.byterindex('oo') # => 1
    'foo'.byterindex('ooo') # => nil

Returns the `Integer` byte-based index of the last match for the given `Regexp` `regexp`, or `nil` if none found:

    'foo'.byterindex(/f/) # => 0
    'foo'.byterindex(/o/) # => 2
    'foo'.byterindex(/oo/) # => 1
    'foo'.byterindex(/ooo/) # => nil

The last match means starting at the possible last position, not the last of longest matches.

    'foo'.byterindex(/o+/) # => 2
    $~ #=> #<MatchData "o">

To get the last longest match, needs to combine with negative lookbehind.

    'foo'.byterindex(/(?<!o)o+/) # => 1
    $~ #=> #<MatchData "oo">

Or `String#byteindex` with negative lookforward.

    'foo'.byteindex(/o+(?!.*o)/) # => 1
    $~ #=> #<MatchData "oo">

`Integer` argument `offset`, if given and non-negative, specifies the maximum starting byte-based position in the string to end the search:

    'foo'.byterindex('o', 0) # => nil
    'foo'.byterindex('o', 1) # => 1
    'foo'.byterindex('o', 2) # => 2
    'foo'.byterindex('o', 3) # => 2

If `offset` is a negative `Integer`, the maximum starting position in the string to end the search is the sum of the string’s length and `offset`:

    'foo'.byterindex('o', -1) # => 2
    'foo'.byterindex('o', -2) # => 1
    'foo'.byterindex('o', -3) # => nil
    'foo'.byterindex('o', -4) # => nil

If `offset` does not land on character (codepoint) boundary, `IndexError` is raised.

Related: `String#byteindex`.

bytes → array_of_bytes
Source

    static VALUE
    rb_str_bytes(VALUE str)
    {
        VALUE ary = WANTARRAY("bytes", RSTRING_LEN(str));
        return rb_str_enumerate_bytes(str, ary);
    }

Returns an array of the bytes in `self`:

    'hello'.bytes # => [104, 101, 108, 108, 111]
    'тест'.bytes  # => [209, 130, 208, 181, 209, 129, 209, 130]
    'こんにちは'.bytes
    # => [227, 129, 147, 227, 130, 147, 227, 129, 171, 227, 129, 161, 227, 129, 175]

bytesize → integer
Source

    VALUE
    rb_str_bytesize(VALUE str)
    {
        return LONG2NUM(RSTRING_LEN(str));
    }

Returns the count of bytes (not characters) in `self`:

    'foo'.bytesize        # => 3
    'тест'.bytesize       # => 8
    'こんにちは'.bytesize   # => 15

Contrast with `String#length`:

    'foo'.length       # => 3
    'тест'.length      # => 4
    'こんにちは'.length  # => 5

byteslice(index, length = 1) → string or nil
byteslice(range) → string or nil
Source

    static VALUE
    rb_str_byteslice(int argc, VALUE *argv, VALUE str)
    {
        if (argc == 2) {
            long beg = NUM2LONG(argv[0]);
            long len = NUM2LONG(argv[1]);
            return str_byte_substr(str, beg, len, TRUE);
        }
        rb_check_arity(argc, 1, 2);
        return str_byte_aref(str, argv[0]);
    }

Returns a substring of `self`, or `nil` if the substring cannot be constructed.

With integer arguments `index` and `length` given, returns the substring beginning at the given `index` of the given `length` (if possible), or `nil` if `length` is negative or `index` falls outside of `self`:

    s = '0123456789' # => "0123456789"
    s.byteslice(2)   # => "2"
    s.byteslice(200) # => nil
    s.byteslice(4, 3)  # => "456"
    s.byteslice(4, 30) # => "456789"
    s.byteslice(4, -1) # => nil
    s.byteslice(40, 2) # => nil

In either case above, counts backwards from the end of `self` if `index` is negative:

    s = '0123456789'   # => "0123456789"
    s.byteslice(-4)    # => "6"
    s.byteslice(-4, 3) # => "678"

With `Range` argument `range` given, returns `byteslice(range.begin, range.size)`:

    s = '0123456789'    # => "0123456789"
    s.byteslice(4..6)   # => "456"
    s.byteslice(-6..-4) # => "456"
    s.byteslice(5..2)   # => "" # range.size is zero.
    s.byteslice(40..42) # => nil

In all cases, a returned string has the same encoding as `self`:

    s.encoding              # => #<Encoding:UTF-8>
    s.byteslice(4).encoding # => #<Encoding:UTF-8>

bytesplice(index, length, str) → string
bytesplice(index, length, str, str_index, str_length) → string
bytesplice(range, str) → string
bytesplice(range, str, str_range) → string
Source

    static VALUE
    rb_str_bytesplice(int argc, VALUE *argv, VALUE str)
    {
        long beg, len, vbeg, vlen;
        VALUE val;
        int cr;

        rb_check_arity(argc, 2, 5);
        if (!(argc == 2 || argc == 3 || argc == 5)) {
            rb_raise(rb_eArgError, "wrong number of arguments (given %d, expected 2, 3, or 5)", argc);
        }
        if (argc == 2 || (argc == 3 && !RB_INTEGER_TYPE_P(argv[0]))) {
            if (!rb_range_beg_len(argv[0], &beg, &len, RSTRING_LEN(str), 2)) {
                rb_raise(rb_eTypeError, "wrong argument type %s (expected Range)",
                         rb_builtin_class_name(argv[0]));
            }
            val = argv[1];
            StringValue(val);
            if (argc == 2) {
                /* bytesplice(range, str) */
                vbeg = 0;
                vlen = RSTRING_LEN(val);
            }
            else {
                /* bytesplice(range, str, str_range) */
                if (!rb_range_beg_len(argv[2], &vbeg, &vlen, RSTRING_LEN(val), 2)) {
                    rb_raise(rb_eTypeError, "wrong argument type %s (expected Range)",
                             rb_builtin_class_name(argv[2]));
                }
            }
        }
        else {
            beg = NUM2LONG(argv[0]);
            len = NUM2LONG(argv[1]);
            val = argv[2];
            StringValue(val);
            if (argc == 3) {
                /* bytesplice(index, length, str) */
                vbeg = 0;
                vlen = RSTRING_LEN(val);
            }
            else {
                /* bytesplice(index, length, str, str_index, str_length) */
                vbeg = NUM2LONG(argv[3]);
                vlen = NUM2LONG(argv[4]);
            }
        }
        str_check_beg_len(str, &beg, &len);
        str_check_beg_len(val, &vbeg, &vlen);
        str_modify_keep_cr(str);

        if (RB_UNLIKELY(ENCODING_GET_INLINED(str) != ENCODING_GET_INLINED(val))) {
            rb_enc_associate(str, rb_enc_check(str, val));
        }

        rb_str_update_1(str, beg, len, val, vbeg, vlen);
        cr = ENC_CODERANGE_AND(ENC_CODERANGE(str), ENC_CODERANGE(val));
        if (cr != ENC_CODERANGE_BROKEN)
            ENC_CODERANGE_SET(str, cr);
        return str;
    }

Replaces some or all of the content of `self` with `str`, and returns `self`. The portion of the string affected is determined using the same criteria as `String#byteslice`, except that `length` cannot be omitted. If the replacement string is not the same length as the text it is replacing, the string will be adjusted accordingly.

If `str_index` and `str_length`, or `str_range` are given, the content of `self` is replaced by str.byteslice(str_index, str_length) or str.byteslice(str_range); however the substring of `str` is not allocated as a new string.

The form that take an `Integer` will raise an `IndexError` if the value is out of range; the `Range` form will raise a `RangeError`. If the beginning or ending offset does not land on character (codepoint) boundary, an `IndexError` will be raised.

capitalize(*options) → string
Source

    static VALUE
    rb_str_capitalize(int argc, VALUE *argv, VALUE str)
    {
        rb_encoding *enc;
        OnigCaseFoldType flags = ONIGENC_CASE_UPCASE | ONIGENC_CASE_TITLECASE;
        VALUE ret;

        flags = check_case_options(argc, argv, flags);
        enc = str_true_enc(str);
        if (RSTRING_LEN(str) == 0 || !RSTRING_PTR(str)) return str;
        if (flags&ONIGENC_CASE_ASCII_ONLY) {
            ret = rb_str_new(0, RSTRING_LEN(str));
            rb_str_ascii_casemap(str, ret, &flags, enc);
        }
        else {
            ret = rb_str_casemap(str, &flags, enc);
        }
        return ret;
    }

Returns a string containing the characters in `self`; the first character is upcased; the remaining characters are downcased:

    s = 'hello World!' # => "hello World!"
    s.capitalize       # => "Hello world!"

The casing may be affected by the given `options`; see Case Mapping.

Related: `String#capitalize!`.

capitalize!(*options) → self or nil
Source

    static VALUE
    rb_str_capitalize_bang(int argc, VALUE *argv, VALUE str)
    {
        rb_encoding *enc;
        OnigCaseFoldType flags = ONIGENC_CASE_UPCASE | ONIGENC_CASE_TITLECASE;

        flags = check_case_options(argc, argv, flags);
        str_modify_keep_cr(str);
        enc = str_true_enc(str);
        if (RSTRING_LEN(str) == 0 || !RSTRING_PTR(str)) return Qnil;
        if (flags&ONIGENC_CASE_ASCII_ONLY)
            rb_str_ascii_casemap(str, str, &flags, enc);
        else
            str_shared_replace(str, rb_str_casemap(str, &flags, enc));

        if (ONIGENC_CASE_MODIFIED&flags) return str;
        return Qnil;
    }

Upcases the first character in `self`; downcases the remaining characters; returns `self` if any changes were made, `nil` otherwise:

    s = 'hello World!' # => "hello World!"
    s.capitalize!      # => "Hello world!"
    s                  # => "Hello world!"
    s.capitalize!      # => nil

The casing may be affected by the given `options`; see Case Mapping.

Related: `String#capitalize`.

casecmp(other_string) → -1, 0, 1, or nil
Source

    static VALUE
    rb_str_casecmp(VALUE str1, VALUE str2)
    {
        VALUE s = rb_check_string_type(str2);
        if (NIL_P(s)) {
            return Qnil;
        }
        return str_casecmp(str1, s);
    }

Compares `self.downcase` and `other_string.downcase`; returns:

- -1 if `other_string.downcase` is larger.

- 0 if the two are equal.

- 1 if `other_string.downcase` is smaller.

- `nil` if the two are incomparable.

Examples:

    'foo'.casecmp('foo') # => 0
    'foo'.casecmp('food') # => -1
    'food'.casecmp('foo') # => 1
    'FOO'.casecmp('foo') # => 0
    'foo'.casecmp('FOO') # => 0
    'foo'.casecmp(1) # => nil

See Case Mapping.

Related: `String#casecmp?`.

casecmp?(other_string) → true, false, or nil
Source

    static VALUE
    rb_str_casecmp_p(VALUE str1, VALUE str2)
    {
        VALUE s = rb_check_string_type(str2);
        if (NIL_P(s)) {
            return Qnil;
        }
        return str_casecmp_p(str1, s);
    }

Returns `true` if `self` and `other_string` are equal after Unicode case folding, otherwise `false`:

    'foo'.casecmp?('foo') # => true
    'foo'.casecmp?('food') # => false
    'food'.casecmp?('foo') # => false
    'FOO'.casecmp?('foo') # => true
    'foo'.casecmp?('FOO') # => true

Returns `nil` if the two values are incomparable:

    'foo'.casecmp?(1) # => nil

See Case Mapping.

Related: `String#casecmp`.

center(size, pad_string = ' ') → new_string
Source

    static VALUE
    rb_str_center(int argc, VALUE *argv, VALUE str)
    {
        return rb_str_justify(argc, argv, str, 'c');
    }

Returns a centered copy of `self`.

If integer argument `size` is greater than the size (in characters) of `self`, returns a new string of length `size` that is a copy of `self`, centered and padded on both ends with `pad_string`:

    'hello'.center(10)       # => "  hello   "
    '  hello'.center(10)     # => "   hello  "
    'hello'.center(10, 'ab') # => "abhelloaba"
    'тест'.center(10)        # => "   тест   "
    'こんにちは'.center(10)    # => "  こんにちは   "

If `size` is not greater than the size of `self`, returns a copy of `self`:

    'hello'.center(5)  # => "hello"
    'hello'.center(1)  # => "hello"

Related: `String#ljust`, `String#rjust`.

chars → array_of_characters
Source

    static VALUE
    rb_str_chars(VALUE str)
    {
        VALUE ary = WANTARRAY("chars", rb_str_strlen(str));
        return rb_str_enumerate_chars(str, ary);
    }

Returns an array of the characters in `self`:

    'hello'.chars     # => ["h", "e", "l", "l", "o"]
    'тест'.chars      # => ["т", "е", "с", "т"]
    'こんにちは'.chars # => ["こ", "ん", "に", "ち", "は"]

chomp(line_sep = $/) → new_string
Source

    static VALUE
    rb_str_chomp(int argc, VALUE *argv, VALUE str)
    {
        VALUE rs = chomp_rs(argc, argv);
        if (NIL_P(rs)) return str_duplicate(rb_cString, str);
        return rb_str_subseq(str, 0, chompped_length(str, rs));
    }

Returns a new string copied from `self`, with trailing characters possibly removed:

When `line_sep` is `"\n"`, removes the last one or two characters if they are `"\r"`, `"\n"`, or `"\r\n"` (but not `"\n\r"`):

    $/                    # => "\n"
    "abc\r".chomp         # => "abc"
    "abc\n".chomp         # => "abc"
    "abc\r\n".chomp       # => "abc"
    "abc\n\r".chomp       # => "abc\n"
    "тест\r\n".chomp      # => "тест"
    "こんにちは\r\n".chomp  # => "こんにちは"

When `line_sep` is `''` (an empty string), removes multiple trailing occurrences of `"\n"` or `"\r\n"` (but not `"\r"` or `"\n\r"`):

    "abc\n\n\n".chomp('')           # => "abc"
    "abc\r\n\r\n\r\n".chomp('')     # => "abc"
    "abc\n\n\r\n\r\n\n\n".chomp('') # => "abc"
    "abc\n\r\n\r\n\r".chomp('')     # => "abc\n\r\n\r\n\r"
    "abc\r\r\r".chomp('')           # => "abc\r\r\r"

When `line_sep` is neither `"\n"` nor `''`, removes a single trailing line separator if there is one:

    'abcd'.chomp('d')  # => "abc"
    'abcdd'.chomp('d') # => "abcd"

chomp!(line_sep = $/) → self or nil
Source

    static VALUE
    rb_str_chomp_bang(int argc, VALUE *argv, VALUE str)
    {
        VALUE rs;
        str_modifiable(str);
        if (RSTRING_LEN(str) == 0 && argc < 2) return Qnil;
        rs = chomp_rs(argc, argv);
        if (NIL_P(rs)) return Qnil;
        return rb_str_chomp_string(str, rs);
    }

Like `String#chomp`, but modifies `self` in place; returns `nil` if no modification made, `self` otherwise.

chop → new_string
Source

    static VALUE
    rb_str_chop(VALUE str)
    {
        return rb_str_subseq(str, 0, chopped_length(str));
    }

Returns a new string copied from `self`, with trailing characters possibly removed.

Removes `"\r\n"` if those are the last two characters.

    "abc\r\n".chop      # => "abc"
    "тест\r\n".chop     # => "тест"
    "こんにちは\r\n".chop # => "こんにちは"

Otherwise removes the last character if it exists.

    'abcd'.chop     # => "abc"
    'тест'.chop     # => "тес"
    'こんにちは'.chop # => "こんにち"
    ''.chop         # => ""

If you only need to remove the newline separator at the end of the string, `String#chomp` is a better alternative.

chop! → self or nil
Source

    static VALUE
    rb_str_chop_bang(VALUE str)
    {
        str_modify_keep_cr(str);
        if (RSTRING_LEN(str) > 0) {
            long len;
            len = chopped_length(str);
            STR_SET_LEN(str, len);
            TERM_FILL(&RSTRING_PTR(str)[len], TERM_LEN(str));
            if (ENC_CODERANGE(str) != ENC_CODERANGE_7BIT) {
                ENC_CODERANGE_CLEAR(str);
            }
            return str;
        }
        return Qnil;
    }

Like `String#chop`, but modifies `self` in place; returns `nil` if `self` is empty, `self` otherwise.

Related: `String#chomp!`.

chr → string
Source

    static VALUE
    rb_str_chr(VALUE str)
    {
        return rb_str_substr(str, 0, 1);
    }

Returns a string containing the first character of `self`:

    s = 'foo' # => "foo"
    s.chr     # => "f"

clear → self
Source

    static VALUE
    rb_str_clear(VALUE str)
    {
        str_discard(str);
        STR_SET_EMBED(str);
        STR_SET_LEN(str, 0);
        RSTRING_PTR(str)[0] = 0;
        if (rb_enc_asciicompat(STR_ENC_GET(str)))
            ENC_CODERANGE_SET(str, ENC_CODERANGE_7BIT);
        else
            ENC_CODERANGE_SET(str, ENC_CODERANGE_VALID);
        return str;
    }

Removes the contents of `self`:

    s = 'foo' # => "foo"
    s.clear   # => ""

codepoints → array_of_integers
Source

    static VALUE
    rb_str_codepoints(VALUE str)
    {
        VALUE ary = WANTARRAY("codepoints", rb_str_strlen(str));
        return rb_str_enumerate_codepoints(str, ary);
    }

Returns an array of the codepoints in `self`; each codepoint is the integer value for a character:

    'hello'.codepoints     # => [104, 101, 108, 108, 111]
    'тест'.codepoints      # => [1090, 1077, 1089, 1090]
    'こんにちは'.codepoints # => [12371, 12435, 12395, 12385, 12399]

concat(*objects) → string
Source

    static VALUE
    rb_str_concat_multi(int argc, VALUE *argv, VALUE str)
    {
        str_modifiable(str);

        if (argc == 1) {
            return rb_str_concat(str, argv[0]);
        }
        else if (argc > 1) {
            int i;
            VALUE arg_str = rb_str_tmp_new(0);
            rb_enc_copy(arg_str, str);
            for (i = 0; i < argc; i++) {
                rb_str_concat(arg_str, argv[i]);
            }
            rb_str_buf_append(str, arg_str);
        }

        return str;
    }

Concatenates each object in `objects` to `self` and returns `self`:

    s = 'foo'
    s.concat('bar', 'baz') # => "foobarbaz"
    s                      # => "foobarbaz"

For each given object `object` that is an `Integer`, the value is considered a codepoint and converted to a character before concatenation:

    s = 'foo'
    s.concat(32, 'bar', 32, 'baz') # => "foo bar baz"

Related: `String#<<`, which takes a single argument.

count(*selectors) → integer
Source

    static VALUE
    rb_str_count(int argc, VALUE *argv, VALUE str)
    {
        char table[TR_TABLE_SIZE];
        rb_encoding *enc = 0;
        VALUE del = 0, nodel = 0, tstr;
        char *s, *send;
        int i;
        int ascompat;
        size_t n = 0;

        rb_check_arity(argc, 1, UNLIMITED_ARGUMENTS);

        tstr = argv[0];
        StringValue(tstr);
        enc = rb_enc_check(str, tstr);
        if (argc == 1) {
            const char *ptstr;
            if (RSTRING_LEN(tstr) == 1 && rb_enc_asciicompat(enc) &&
                (ptstr = RSTRING_PTR(tstr),
                 ONIGENC_IS_ALLOWED_REVERSE_MATCH(enc, (const unsigned char *)ptstr, (const unsigned char *)ptstr+1)) &&
                !is_broken_string(str)) {
                int clen;
                unsigned char c = rb_enc_codepoint_len(ptstr, ptstr+1, &clen, enc);

                s = RSTRING_PTR(str);
                if (!s || RSTRING_LEN(str) == 0) return INT2FIX(0);
                send = RSTRING_END(str);
                while (s < send) {
                    if (*(unsigned char*)s++ == c) n++;
                }
                return SIZET2NUM(n);
            }
        }

        tr_setup_table(tstr, table, TRUE, &del, &nodel, enc);
        for (i=1; i<argc; i++) {
            tstr = argv[i];
            StringValue(tstr);
            enc = rb_enc_check(str, tstr);
            tr_setup_table(tstr, table, FALSE, &del, &nodel, enc);
        }

        s = RSTRING_PTR(str);
        if (!s || RSTRING_LEN(str) == 0) return INT2FIX(0);
        send = RSTRING_END(str);
        ascompat = rb_enc_asciicompat(enc);
        while (s < send) {
            unsigned int c;

            if (ascompat && (c = *(unsigned char*)s) < 0x80) {
                if (table[c]) {
                    n++;
                }
                s++;
            }
            else {
                int clen;
                c = rb_enc_codepoint_len(s, send, &clen, enc);
                if (tr_find(c, table, del, nodel)) {
                    n++;
                }
                s += clen;
            }
        }

        return SIZET2NUM(n);
    }

Returns the total number of characters in `self` that are specified by the given `selectors` (see Multiple Character Selectors):

    a = "hello world"
    a.count "lo"                   #=> 5
    a.count "lo", "o"              #=> 2
    a.count "hello", "^l"          #=> 4
    a.count "ej-m"                 #=> 4

    "hello^world".count "\\^aeiou" #=> 4
    "hello-world".count "a\\-eo"   #=> 4

    c = "hello world\\r\\n"
    c.count "\\"                   #=> 2
    c.count "\\A"                  #=> 0
    c.count "X-\\w"                #=> 3

crypt(salt_str) → new_string
Source

    static VALUE
    rb_str_crypt(VALUE str, VALUE salt)
    {
    #ifdef HAVE_CRYPT_R
        VALUE databuf;
        struct crypt_data *data;
    #   define CRYPT_END() ALLOCV_END(databuf)
    #else
        extern char *crypt(const char *, const char *);
    #   define CRYPT_END() rb_nativethread_lock_unlock(&crypt_mutex.lock)
    #endif
        VALUE result;
        const char *s, *saltp;
        char *res;
    #ifdef BROKEN_CRYPT
        char salt_8bit_clean[3];
    #endif

        StringValue(salt);
        mustnot_wchar(str);
        mustnot_wchar(salt);
        s = StringValueCStr(str);
        saltp = RSTRING_PTR(salt);
        if (RSTRING_LEN(salt) < 2 || !saltp[0] || !saltp[1]) {
            rb_raise(rb_eArgError, "salt too short (need >=2 bytes)");
        }

    #ifdef BROKEN_CRYPT
        if (!ISASCII((unsigned char)saltp[0]) || !ISASCII((unsigned char)saltp[1])) {
            salt_8bit_clean[0] = saltp[0] & 0x7f;
            salt_8bit_clean[1] = saltp[1] & 0x7f;
            salt_8bit_clean[2] = '\0';
            saltp = salt_8bit_clean;
        }
    #endif
    #ifdef HAVE_CRYPT_R
        data = ALLOCV(databuf, sizeof(struct crypt_data));
    # ifdef HAVE_STRUCT_CRYPT_DATA_INITIALIZED
        data->initialized = 0;
    # endif
        res = crypt_r(s, saltp, data);
    #else
        crypt_mutex_initialize();
        rb_nativethread_lock_lock(&crypt_mutex.lock);
        res = crypt(s, saltp);
    #endif
        if (!res) {
            int err = errno;
            CRYPT_END();
            rb_syserr_fail(err, "crypt");
        }
        result = rb_str_new_cstr(res);
        CRYPT_END();
        return result;
    }

Returns the string generated by calling `crypt(3)` standard library function with `str` and `salt_str`, in this order, as its arguments. Please do not use this method any longer. It is legacy; provided only for backward compatibility with ruby scripts in earlier days. It is bad to use in contemporary programs for several reasons:

- Behaviour of C’s `crypt(3)` depends on the OS it is run. The generated string lacks data portability.

- On some OSes such as Mac OS, `crypt(3)` never fails (i.e. silently ends up in unexpected results).

- On some OSes such as Mac OS, `crypt(3)` is not thread safe.

- So-called “traditional” usage of `crypt(3)` is very very very weak. According to its manpage, Linux’s traditional `crypt(3)` output has only 2**56 variations; too easy to brute force today. And this is the default behaviour.

- In order to make things robust some OSes implement so-called “modular” usage. To go through, you have to do a complex build-up of the `salt_str` parameter, by hand. Failure in generation of a proper salt string tends not to yield any errors; typos in parameters are normally not detectable.

  - For instance, in the following example, the second invocation of `String#crypt` is wrong; it has a typo in “round=” (lacks “s”). However the call does not fail and something unexpected is generated.

        "foo".crypt("$5$rounds=1000$salt$") # OK, proper usage
        "foo".crypt("$5$round=1000$salt$")  # Typo not detected

- Even in the “modular” mode, some hash functions are considered archaic and no longer recommended at all; for instance module `$1$` is officially abandoned by its author: see phk.freebsd.dk/sagas/md5crypt_eol/ . For another instance module `$3$` is considered completely broken: see the manpage of FreeBSD.

- On some OS such as Mac OS, there is no modular mode. Yet, as written above, `crypt(3)` on Mac OS never fails. This means even if you build up a proper salt string it generates a traditional DES hash anyways, and there is no way for you to be aware of.

      "foo".crypt("$5$rounds=1000$salt$") # => "$5fNPQMxC5j6."

If for some reason you cannot migrate to other secure contemporary password hashing algorithms, install the string-crypt gem and `require 'string/crypt'` to continue using it.

-string → frozen_string
dedup → frozen_string

Returns a frozen, possibly pre-existing copy of the string.

The returned `String` will be deduplicated as long as it does not have any instance variables set on it and is not a `String` subclass.

Note that `-string` variant is more convenient for defining constants:

    FILENAME = -'config/database.yml'

while `dedup` is better suitable for using the method in chains of calculations:

    @url_list.concat(urls.map(&:dedup))

Alias for: -@
delete(*selectors) → new_string
Source

    static VALUE
    rb_str_delete(int argc, VALUE *argv, VALUE str)
    {
        str = str_duplicate(rb_cString, str);
        rb_str_delete_bang(argc, argv, str);
        return str;
    }

Returns a copy of `self` with characters specified by `selectors` removed (see Multiple Character Selectors):

    "hello".delete "l","lo"        #=> "heo"
    "hello".delete "lo"            #=> "he"
    "hello".delete "aeiou", "^e"   #=> "hell"
    "hello".delete "ej-m"          #=> "ho"

delete!(*selectors) → self or nil
Source

    static VALUE
    rb_str_delete_bang(int argc, VALUE *argv, VALUE str)
    {
        char squeez[TR_TABLE_SIZE];
        rb_encoding *enc = 0;
        char *s, *send, *t;
        VALUE del = 0, nodel = 0;
        int modify = 0;
        int i, ascompat, cr;

        if (RSTRING_LEN(str) == 0 || !RSTRING_PTR(str)) return Qnil;
        rb_check_arity(argc, 1, UNLIMITED_ARGUMENTS);
        for (i=0; i<argc; i++) {
            VALUE s = argv[i];

            StringValue(s);
            enc = rb_enc_check(str, s);
            tr_setup_table(s, squeez, i==0, &del, &nodel, enc);
        }

        str_modify_keep_cr(str);
        ascompat = rb_enc_asciicompat(enc);
        s = t = RSTRING_PTR(str);
        send = RSTRING_END(str);
        cr = ascompat ? ENC_CODERANGE_7BIT : ENC_CODERANGE_VALID;
        while (s < send) {
            unsigned int c;
            int clen;

            if (ascompat && (c = *(unsigned char*)s) < 0x80) {
                if (squeez[c]) {
                    modify = 1;
                }
                else {
                    if (t != s) *t = c;
                    t++;
                }
                s++;
            }
            else {
                c = rb_enc_codepoint_len(s, send, &clen, enc);

                if (tr_find(c, squeez, del, nodel)) {
                    modify = 1;
                }
                else {
                    if (t != s) rb_enc_mbcput(c, t, enc);
                    t += clen;
                    if (cr == ENC_CODERANGE_7BIT) cr = ENC_CODERANGE_VALID;
                }
                s += clen;
            }
        }
        TERM_FILL(t, TERM_LEN(str));
        STR_SET_LEN(str, t - RSTRING_PTR(str));
        ENC_CODERANGE_SET(str, cr);

        if (modify) return str;
        return Qnil;
    }

Like `String#delete`, but modifies `self` in place. Returns `self` if any changes were made, `nil` otherwise.

delete_prefix(prefix) → new_string
Source

    static VALUE
    rb_str_delete_prefix(VALUE str, VALUE prefix)
    {
        long prefixlen;

        prefixlen = deleted_prefix_length(str, prefix);
        if (prefixlen <= 0) return str_duplicate(rb_cString, str);

        return rb_str_subseq(str, prefixlen, RSTRING_LEN(str) - prefixlen);
    }

Returns a copy of `self` with leading substring `prefix` removed:

    'hello'.delete_prefix('hel')      # => "lo"
    'hello'.delete_prefix('llo')      # => "hello"
    'тест'.delete_prefix('те')        # => "ст"
    'こんにちは'.delete_prefix('こん')  # => "にちは"

Related: `String#delete_prefix!`, `String#delete_suffix`.

delete_prefix!(prefix) → self or nil
Source

    static VALUE
    rb_str_delete_prefix_bang(VALUE str, VALUE prefix)
    {
        long prefixlen;
        str_modify_keep_cr(str);

        prefixlen = deleted_prefix_length(str, prefix);
        if (prefixlen <= 0) return Qnil;

        return rb_str_drop_bytes(str, prefixlen);
    }

Like `String#delete_prefix`, except that `self` is modified in place. Returns `self` if the prefix is removed, `nil` otherwise.

delete_suffix(suffix) → new_string
Source

    static VALUE
    rb_str_delete_suffix(VALUE str, VALUE suffix)
    {
        long suffixlen;

        suffixlen = deleted_suffix_length(str, suffix);
        if (suffixlen <= 0) return str_duplicate(rb_cString, str);

        return rb_str_subseq(str, 0, RSTRING_LEN(str) - suffixlen);
    }

Returns a copy of `self` with trailing substring `suffix` removed:

    'hello'.delete_suffix('llo')      # => "he"
    'hello'.delete_suffix('hel')      # => "hello"
    'тест'.delete_suffix('ст')        # => "те"
    'こんにちは'.delete_suffix('ちは')  # => "こんに"

Related: `String#delete_suffix!`, `String#delete_prefix`.

delete_suffix!(suffix) → self or nil
Source

    static VALUE
    rb_str_delete_suffix_bang(VALUE str, VALUE suffix)
    {
        long olen, suffixlen, len;
        str_modifiable(str);

        suffixlen = deleted_suffix_length(str, suffix);
        if (suffixlen <= 0) return Qnil;

        olen = RSTRING_LEN(str);
        str_modify_keep_cr(str);
        len = olen - suffixlen;
        STR_SET_LEN(str, len);
        TERM_FILL(&RSTRING_PTR(str)[len], TERM_LEN(str));
        if (ENC_CODERANGE(str) != ENC_CODERANGE_7BIT) {
            ENC_CODERANGE_CLEAR(str);
        }
        return str;
    }

Like `String#delete_suffix`, except that `self` is modified in place. Returns `self` if the suffix is removed, `nil` otherwise.

downcase(*options) → string
Source

    static VALUE
    rb_str_downcase(int argc, VALUE *argv, VALUE str)
    {
        rb_encoding *enc;
        OnigCaseFoldType flags = ONIGENC_CASE_DOWNCASE;
        VALUE ret;

        flags = check_case_options(argc, argv, flags);
        enc = str_true_enc(str);
        if (case_option_single_p(flags, enc, str)) {
            ret = rb_str_new(RSTRING_PTR(str), RSTRING_LEN(str));
            str_enc_copy_direct(ret, str);
            downcase_single(ret);
        }
        else if (flags&ONIGENC_CASE_ASCII_ONLY) {
            ret = rb_str_new(0, RSTRING_LEN(str));
            rb_str_ascii_casemap(str, ret, &flags, enc);
        }
        else {
            ret = rb_str_casemap(str, &flags, enc);
        }

        return ret;
    }

Returns a string containing the downcased characters in `self`:

    s = 'Hello World!' # => "Hello World!"
    s.downcase         # => "hello world!"

The casing may be affected by the given `options`; see Case Mapping.

Related: `String#downcase!`, `String#upcase`, `String#upcase!`.

downcase!(*options) → self or nil
Source

    static VALUE
    rb_str_downcase_bang(int argc, VALUE *argv, VALUE str)
    {
        rb_encoding *enc;
        OnigCaseFoldType flags = ONIGENC_CASE_DOWNCASE;

        flags = check_case_options(argc, argv, flags);
        str_modify_keep_cr(str);
        enc = str_true_enc(str);
        if (case_option_single_p(flags, enc, str)) {
            if (downcase_single(str))
                flags |= ONIGENC_CASE_MODIFIED;
        }
        else if (flags&ONIGENC_CASE_ASCII_ONLY)
            rb_str_ascii_casemap(str, str, &flags, enc);
        else
            str_shared_replace(str, rb_str_casemap(str, &flags, enc));

        if (ONIGENC_CASE_MODIFIED&flags) return str;
        return Qnil;
    }

Downcases the characters in `self`; returns `self` if any changes were made, `nil` otherwise:

    s = 'Hello World!' # => "Hello World!"
    s.downcase!        # => "hello world!"
    s                  # => "hello world!"
    s.downcase!        # => nil

The casing may be affected by the given `options`; see Case Mapping.

Related: `String#downcase`, `String#upcase`, `String#upcase!`.

dump → string
Source

    VALUE
    rb_str_dump(VALUE str)
    {
        int encidx = rb_enc_get_index(str);
        rb_encoding *enc = rb_enc_from_index(encidx);
        long len;
        const char *p, *pend;
        char *q, *qend;
        VALUE result;
        int u8 = (encidx == rb_utf8_encindex());
        static const char nonascii_suffix[] = ".dup.force_encoding(\"%s\")";

        len = 2;                    /* "" */
        if (!rb_enc_asciicompat(enc)) {
            len += strlen(nonascii_suffix) - rb_strlen_lit("%s");
            len += strlen(enc->name);
        }

        p = RSTRING_PTR(str); pend = p + RSTRING_LEN(str);
        while (p < pend) {
            int clen;
            unsigned char c = *p++;

            switch (c) {
              case '"':  case '\\':
              case '\n': case '\r':
              case '\t': case '\f':
              case '\013': case '\010': case '\007': case '\033':
                clen = 2;
                break;

              case '#':
                clen = IS_EVSTR(p, pend) ? 2 : 1;
                break;

              default:
                if (ISPRINT(c)) {
                    clen = 1;
                }
                else {
                    if (u8 && c > 0x7F) {   /* \u notation */
                        int n = rb_enc_precise_mbclen(p-1, pend, enc);
                        if (MBCLEN_CHARFOUND_P(n)) {
                            unsigned int cc = rb_enc_mbc_to_codepoint(p-1, pend, enc);
                            if (cc <= 0xFFFF)
                                clen = 6;  /* \uXXXX */
                            else if (cc <= 0xFFFFF)
                                clen = 9;  /* \u{XXXXX} */
                            else
                                clen = 10; /* \u{XXXXXX} */
                            p += MBCLEN_CHARFOUND_LEN(n)-1;
                            break;
                        }
                    }
                    clen = 4;       /* \xNN */
                }
                break;
            }

            if (clen > LONG_MAX - len) {
                rb_raise(rb_eRuntimeError, "string size too big");
            }
            len += clen;
        }

        result = rb_str_new(0, len);
        p = RSTRING_PTR(str); pend = p + RSTRING_LEN(str);
        q = RSTRING_PTR(result); qend = q + len + 1;

        *q++ = '"';
        while (p < pend) {
            unsigned char c = *p++;

            if (c == '"' || c == '\\') {
                *q++ = '\\';
                *q++ = c;
            }
            else if (c == '#') {
                if (IS_EVSTR(p, pend)) *q++ = '\\';
                *q++ = '#';
            }
            else if (c == '\n') {
                *q++ = '\\';
                *q++ = 'n';
            }
            else if (c == '\r') {
                *q++ = '\\';
                *q++ = 'r';
            }
            else if (c == '\t') {
                *q++ = '\\';
                *q++ = 't';
            }
            else if (c == '\f') {
                *q++ = '\\';
                *q++ = 'f';
            }
            else if (c == '\013') {
                *q++ = '\\';
                *q++ = 'v';
            }
            else if (c == '\010') {
                *q++ = '\\';
                *q++ = 'b';
            }
            else if (c == '\007') {
                *q++ = '\\';
                *q++ = 'a';
            }
            else if (c == '\033') {
                *q++ = '\\';
                *q++ = 'e';
            }
            else if (ISPRINT(c)) {
                *q++ = c;
            }
            else {
                *q++ = '\\';
                if (u8) {
                    int n = rb_enc_precise_mbclen(p-1, pend, enc) - 1;
                    if (MBCLEN_CHARFOUND_P(n)) {
                        int cc = rb_enc_mbc_to_codepoint(p-1, pend, enc);
                        p += n;
                        if (cc <= 0xFFFF)
                            snprintf(q, qend-q, "u%04X", cc);    /* \uXXXX */
                        else
                            snprintf(q, qend-q, "u{%X}", cc);  /* \u{XXXXX} or \u{XXXXXX} */
                        q += strlen(q);
                        continue;
                    }
                }
                snprintf(q, qend-q, "x%02X", c);
                q += 3;
            }
        }
        *q++ = '"';
        *q = '\0';
        if (!rb_enc_asciicompat(enc)) {
            snprintf(q, qend-q, nonascii_suffix, enc->name);
            encidx = rb_ascii8bit_encindex();
        }
        /* result from dump is ASCII */
        rb_enc_associate_index(result, encidx);
        ENC_CODERANGE_SET(result, ENC_CODERANGE_7BIT);
        return result;
    }

Returns a printable version of `self`, enclosed in double-quotes, with special characters escaped, and with non-printing characters replaced by hexadecimal notation:

    "hello \n ''".dump    # => "\"hello \\n ''\""
    "\f\x00\xff\\\"".dump # => "\"\\f\\x00\\xFF\\\\\\\"\""

Related: `String#undump` (inverse of `String#dump`).

each_byte {|byte| ... } → self
each_byte → enumerator
Source

    static VALUE
    rb_str_each_byte(VALUE str)
    {
        RETURN_SIZED_ENUMERATOR(str, 0, 0, rb_str_each_byte_size);
        return rb_str_enumerate_bytes(str, 0);
    }

Calls the given block with each successive byte from `self`; returns `self`:

    'hello'.each_byte {|byte| print byte, ' ' }
    print "\n"
    'тест'.each_byte {|byte| print byte, ' ' }
    print "\n"
    'こんにちは'.each_byte {|byte| print byte, ' ' }
    print "\n"

Output:

    104 101 108 108 111
    209 130 208 181 209 129 209 130
    227 129 147 227 130 147 227 129 171 227 129 161 227 129 175

Returns an enumerator if no block is given.

each_char {|c| ... } → self
each_char → enumerator
Source

    static VALUE
    rb_str_each_char(VALUE str)
    {
        RETURN_SIZED_ENUMERATOR(str, 0, 0, rb_str_each_char_size);
        return rb_str_enumerate_chars(str, 0);
    }

Calls the given block with each successive character from `self`; returns `self`:

    'hello'.each_char {|char| print char, ' ' }
    print "\n"
    'тест'.each_char {|char| print char, ' ' }
    print "\n"
    'こんにちは'.each_char {|char| print char, ' ' }
    print "\n"

Output:

    h e l l o
    т е с т
    こ ん に ち は

Returns an enumerator if no block is given.

each_codepoint {|integer| ... } → self
each_codepoint → enumerator
Source

    static VALUE
    rb_str_each_codepoint(VALUE str)
    {
        RETURN_SIZED_ENUMERATOR(str, 0, 0, rb_str_each_char_size);
        return rb_str_enumerate_codepoints(str, 0);
    }

Calls the given block with each successive codepoint from `self`; each codepoint is the integer value for a character; returns `self`:

    'hello'.each_codepoint {|codepoint| print codepoint, ' ' }
    print "\n"
    'тест'.each_codepoint {|codepoint| print codepoint, ' ' }
    print "\n"
    'こんにちは'.each_codepoint {|codepoint| print codepoint, ' ' }
    print "\n"

Output:

    104 101 108 108 111
    1090 1077 1089 1090
    12371 12435 12395 12385 12399

Returns an enumerator if no block is given.

each_grapheme_cluster {|gc| ... } → self
each_grapheme_cluster → enumerator
Source

    static VALUE
    rb_str_each_grapheme_cluster(VALUE str)
    {
        RETURN_SIZED_ENUMERATOR(str, 0, 0, rb_str_each_grapheme_cluster_size);
        return rb_str_enumerate_grapheme_clusters(str, 0);
    }

Calls the given block with each successive grapheme cluster from `self` (see Unicode Grapheme Cluster Boundaries); returns `self`:

    s = "\u0061\u0308-pqr-\u0062\u0308-xyz-\u0063\u0308" # => "ä-pqr-b̈-xyz-c̈"
    s.each_grapheme_cluster {|gc| print gc, ' ' }

Output:

    ä - p q r - b̈ - x y z - c̈

Returns an enumerator if no block is given.

each_line(line_sep = $/, chomp: false) {|substring| ... } → self
each_line(line_sep = $/, chomp: false) → enumerator
Source

    static VALUE
    rb_str_each_line(int argc, VALUE *argv, VALUE str)
    {
        RETURN_SIZED_ENUMERATOR(str, argc, argv, 0);
        return rb_str_enumerate_lines(argc, argv, str, 0);
    }

With a block given, forms the substrings (“lines”) that are the result of splitting `self` at each occurrence of the given line separator `line_sep`; passes each line to the block; returns `self`:

    s = <<~EOT
    This is the first line.
    This is line two.

    This is line four.
    This is line five.
    EOT

    s.each_line {|line| p line }

Output:

    "This is the first line.\n"
    "This is line two.\n"
    "\n"
    "This is line four.\n"
    "This is line five.\n"

With a different `line_sep`:

    s.each_line(' is ') {|line| p line }

Output:

    "This is "
    "the first line.\nThis is "
    "line two.\n\nThis is "
    "line four.\nThis is "
    "line five.\n"

With `chomp` as `true`, removes the trailing `line_sep` from each line:

    s.each_line(chomp: true) {|line| p line }

Output:

    "This is the first line."
    "This is line two."
    ""
    "This is line four."
    "This is line five."

With an empty string as `line_sep`, forms and passes “paragraphs” by splitting at each occurrence of two or more newlines:

    s.each_line('') {|line| p line }

Output:

    "This is the first line.\nThis is line two.\n\n"
    "This is line four.\nThis is line five.\n"

With no block given, returns an enumerator.

empty? → true or false
Source

    static VALUE
    rb_str_empty(VALUE str)
    {
        return RBOOL(RSTRING_LEN(str) == 0);
    }

Returns `true` if the length of `self` is zero, `false` otherwise:

    "hello".empty? # => false
    " ".empty? # => false
    "".empty? # => true

encode(dst_encoding = Encoding.default_internal, **enc_opts) → string
encode(dst_encoding, src_encoding, **enc_opts) → string
Source

    static VALUE
    str_encode(int argc, VALUE *argv, VALUE str)
    {
        VALUE newstr = str;
        int encidx = str_transcode(argc, argv, &newstr);
        return encoded_dup(newstr, str, encidx);
    }

Returns a copy of `self` transcoded as determined by `dst_encoding`. By default, raises an exception if `self` contains an invalid byte or a character not defined in `dst_encoding`; that behavior may be modified by encoding options; see below.

With no arguments:

- Uses the same encoding if `Encoding.default_internal` is `nil` (the default):

      Encoding.default_internal # => nil
      s = "Ruby\x99".force_encoding('Windows-1252')
      s.encoding                # => #<Encoding:Windows-1252>
      s.bytes                   # => [82, 117, 98, 121, 153]
      t = s.encode              # => "Ruby\x99"
      t.encoding                # => #<Encoding:Windows-1252>
      t.bytes                   # => [82, 117, 98, 121, 226, 132, 162]

- Otherwise, uses the encoding `Encoding.default_internal`:

      Encoding.default_internal = 'UTF-8'
      t = s.encode              # => "Ruby™"
      t.encoding                # => #<Encoding:UTF-8>

With only argument `dst_encoding` given, uses that encoding:

    s = "Ruby\x99".force_encoding('Windows-1252')
    s.encoding            # => #<Encoding:Windows-1252>
    t = s.encode('UTF-8') # => "Ruby™"
    t.encoding            # => #<Encoding:UTF-8>

With arguments `dst_encoding` and `src_encoding` given, interprets `self` using `src_encoding`, encodes the new string using `dst_encoding`:

    s = "Ruby\x99"
    t = s.encode('UTF-8', 'Windows-1252') # => "Ruby™"
    t.encoding                            # => #<Encoding:UTF-8>

Optional keyword arguments `enc_opts` specify encoding options; see Encoding Options.

Please note that, unless `invalid: :replace` option is given, conversion from an encoding `enc` to the same encoding `enc` (independent of whether `enc` is given explicitly or implicitly) is a no-op, i.e. the string is simply copied without any changes, and no exceptions are raised, even if there are invalid bytes.

encode!(dst_encoding = Encoding.default_internal, **enc_opts) → self
encode!(dst_encoding, src_encoding, **enc_opts) → self
Source

    static VALUE
    str_encode_bang(int argc, VALUE *argv, VALUE str)
    {
        VALUE newstr;
        int encidx;

        rb_check_frozen(str);

        newstr = str;
        encidx = str_transcode(argc, argv, &newstr);

        if (encidx < 0) return str;
        if (newstr == str) {
            rb_enc_associate_index(str, encidx);
            return str;
        }
        rb_str_shared_replace(str, newstr);
        return str_encode_associate(str, encidx);
    }

Like `encode`, but applies encoding changes to `self`; returns `self`.

encoding → encoding
Source

    VALUE
    rb_obj_encoding(VALUE obj)
    {
        int idx = rb_enc_get_index(obj);
        if (idx < 0) {
            rb_raise(rb_eTypeError, "unknown encoding");
        }
        return rb_enc_from_encoding_index(idx & ENC_INDEX_MASK);
    }

Returns the `Encoding` object that represents the encoding of obj.

end_with?(*strings) → true or false
Source

    static VALUE
    rb_str_end_with(int argc, VALUE *argv, VALUE str)
    {
        int i;

        for (i=0; i<argc; i++) {
            VALUE tmp = argv[i];
            const char *p, *s, *e;
            long slen, tlen;
            rb_encoding *enc;

            StringValue(tmp);
            enc = rb_enc_check(str, tmp);
            if ((tlen = RSTRING_LEN(tmp)) == 0) return Qtrue;
            if ((slen = RSTRING_LEN(str)) < tlen) continue;
            p = RSTRING_PTR(str);
            e = p + slen;
            s = e - tlen;
            if (!at_char_boundary(p, s, e, enc))
                continue;
            if (memcmp(s, RSTRING_PTR(tmp), tlen) == 0)
                return Qtrue;
        }
        return Qfalse;
    }

Returns whether `self` ends with any of the given `strings`.

Returns `true` if any given string matches the end, `false` otherwise:

    'hello'.end_with?('ello')               #=> true
    'hello'.end_with?('heaven', 'ello')     #=> true
    'hello'.end_with?('heaven', 'paradise') #=> false
    'тест'.end_with?('т')                   # => true
    'こんにちは'.end_with?('は')              # => true

Related: `String#start_with?`.

eql?(object) → true or false
Source

    VALUE
    rb_str_eql(VALUE str1, VALUE str2)
    {
        if (str1 == str2) return Qtrue;
        if (!RB_TYPE_P(str2, T_STRING)) return Qfalse;
        return rb_str_eql_internal(str1, str2);
    }

Returns `true` if `object` has the same length and content; as `self`; `false` otherwise:

    s = 'foo'
    s.eql?('foo') # => true
    s.eql?('food') # => false
    s.eql?('FOO') # => false

Returns `false` if the two strings’ encodings are not compatible:

    "\u{e4 f6 fc}".encode("ISO-8859-1").eql?("\u{c4 d6 dc}") # => false

force_encoding(encoding) → self
Source

    static VALUE
    rb_str_force_encoding(VALUE str, VALUE enc)
    {
        str_modifiable(str);

        rb_encoding *encoding = rb_to_encoding(enc);
        int idx = rb_enc_to_index(encoding);

        // If the encoding is unchanged, we do nothing.
        if (ENCODING_GET(str) == idx) {
            return str;
        }

        rb_enc_associate_index(str, idx);

        // If the coderange was 7bit and the new encoding is ASCII-compatible
        // we can keep the coderange.
        if (ENC_CODERANGE(str) == ENC_CODERANGE_7BIT && encoding && rb_enc_asciicompat(encoding)) {
            return str;
        }

        ENC_CODERANGE_CLEAR(str);
        return str;
    }

Changes the encoding of `self` to `encoding`, which may be a string encoding name or an `Encoding` object; returns self:

    s = 'łał'
    s.bytes                   # => [197, 130, 97, 197, 130]
    s.encoding                # => #<Encoding:UTF-8>
    s.force_encoding('ascii') # => "\xC5\x82a\xC5\x82"
    s.encoding                # => #<Encoding:US-ASCII>

Does not change the underlying bytes:

    s.bytes                   # => [197, 130, 97, 197, 130]

Makes the change even if the given `encoding` is invalid for `self` (as is the change above):

    s.valid_encoding?                 # => false
    s.force_encoding(Encoding::UTF_8) # => "łał"
    s.valid_encoding?                 # => true

getbyte(index) → integer or nil
Source

    VALUE
    rb_str_getbyte(VALUE str, VALUE index)
    {
        long pos = NUM2LONG(index);

        if (pos < 0)
            pos += RSTRING_LEN(str);
        if (pos < 0 ||  RSTRING_LEN(str) <= pos)
            return Qnil;

        return INT2FIX((unsigned char)RSTRING_PTR(str)[pos]);
    }

Returns the byte at zero-based `index` as an integer, or `nil` if `index` is out of range:

    s = 'abcde'   # => "abcde"
    s.getbyte(0)  # => 97
    s.getbyte(-1) # => 101
    s.getbyte(5)  # => nil

Related: `String#setbyte`.

grapheme_clusters → array_of_grapheme_clusters
Source

    static VALUE
    rb_str_grapheme_clusters(VALUE str)
    {
        VALUE ary = WANTARRAY("grapheme_clusters", rb_str_strlen(str));
        return rb_str_enumerate_grapheme_clusters(str, ary);
    }

Returns an array of the grapheme clusters in `self` (see Unicode Grapheme Cluster Boundaries):

    s = "\u0061\u0308-pqr-\u0062\u0308-xyz-\u0063\u0308" # => "ä-pqr-b̈-xyz-c̈"
    s.grapheme_clusters
    # => ["ä", "-", "p", "q", "r", "-", "b̈", "-", "x", "y", "z", "-", "c̈"]

gsub(pattern, replacement) → new_string
gsub(pattern) {|match| ... } → new_string
gsub(pattern) → enumerator
Source

    static VALUE
    rb_str_gsub(int argc, VALUE *argv, VALUE str)
    {
        return str_gsub(argc, argv, str, 0);
    }

Returns a copy of `self` with all occurrences of the given `pattern` replaced.

See Substitution Methods.

Returns an `Enumerator` if no `replacement` and no block given.

Related: `String#sub`, `String#sub!`, `String#gsub!`.

gsub!(pattern, replacement) → self or nil
gsub!(pattern) {|match| ... } → self or nil
gsub!(pattern) → an_enumerator
Source

    static VALUE
    rb_str_gsub_bang(int argc, VALUE *argv, VALUE str)
    {
        str_modify_keep_cr(str);
        return str_gsub(argc, argv, str, 1);
    }

Performs the specified substring replacement(s) on `self`; returns `self` if any replacement occurred, `nil` otherwise.

See Substitution Methods.

Returns an `Enumerator` if no `replacement` and no block given.

Related: `String#sub`, `String#gsub`, `String#sub!`.

hash → integer
Source

    static VALUE
    rb_str_hash_m(VALUE str)
    {
        st_index_t hval = rb_str_hash(str);
        return ST2FIX(hval);
    }

Returns the integer hash value for `self`. The value is based on the length, content and encoding of `self`.

Related: `Object#hash`.

hex → integer
Source

    static VALUE
    rb_str_hex(VALUE str)
    {
        return rb_str_to_inum(str, 16, FALSE);
    }

Interprets the leading substring of `self` as a string of hexadecimal digits (with an optional sign and an optional `0x`) and returns the corresponding number; returns zero if there is no such leading substring:

    '0x0a'.hex        # => 10
    '-1234'.hex       # => -4660
    '0'.hex           # => 0
    'non-numeric'.hex # => 0

Related: `String#oct`.

include?(other_string) → true or false
Source

    VALUE
    rb_str_include(VALUE str, VALUE arg)
    {
        long i;

        StringValue(arg);
        i = rb_str_index(str, arg, 0);

        return RBOOL(i != -1);
    }

Returns `true` if `self` contains `other_string`, `false` otherwise:

    s = 'foo'
    s.include?('f')    # => true
    s.include?('fo')   # => true
    s.include?('food') # => false

index(substring, offset = 0) → integer or nil
index(regexp, offset = 0) → integer or nil
Source

    static VALUE
    rb_str_index_m(int argc, VALUE *argv, VALUE str)
    {
        VALUE sub;
        VALUE initpos;
        rb_encoding *enc = STR_ENC_GET(str);
        long pos;

        if (rb_scan_args(argc, argv, "11", &sub, &initpos) == 2) {
            long slen = str_strlen(str, enc); /* str's enc */
            pos = NUM2LONG(initpos);
            if (pos < 0 ? (pos += slen) < 0 : pos > slen) {
                if (RB_TYPE_P(sub, T_REGEXP)) {
                    rb_backref_set(Qnil);
                }
                return Qnil;
            }
        }
        else {
            pos = 0;
        }

        if (RB_TYPE_P(sub, T_REGEXP)) {
            pos = str_offset(RSTRING_PTR(str), RSTRING_END(str), pos,
                             enc, single_byte_optimizable(str));

            if (rb_reg_search(sub, str, pos, 0) >= 0) {
                VALUE match = rb_backref_get();
                struct re_registers *regs = RMATCH_REGS(match);
                pos = rb_str_sublen(str, BEG(0));
                return LONG2NUM(pos);
            }
        }
        else {
            StringValue(sub);
            pos = rb_str_index(str, sub, pos);
            if (pos >= 0) {
                pos = rb_str_sublen(str, pos);
                return LONG2NUM(pos);
            }
        }
        return Qnil;
    }

Returns the integer index of the first match for the given argument, or `nil` if none found; the search of `self` is forward, and begins at position `offset` (in characters).

With string argument `substring`, returns the index of the first matching substring in `self`:

    'foo'.index('f')         # => 0
    'foo'.index('o')         # => 1
    'foo'.index('oo')        # => 1
    'foo'.index('ooo')       # => nil
    'тест'.index('с')        # => 2
    'こんにちは'.index('ち')   # => 3

With `Regexp` argument `regexp`, returns the index of the first match in `self`:

    'foo'.index(/o./) # => 1
    'foo'.index(/.o/) # => 0

With positive integer `offset`, begins the search at position `offset`:

    'foo'.index('o', 1)        # => 1
    'foo'.index('o', 2)        # => 2
    'foo'.index('o', 3)        # => nil
    'тест'.index('с', 1)       # => 2
    'こんにちは'.index('ち', 2)  # => 3

With negative integer `offset`, selects the search position by counting backward from the end of `self`:

    'foo'.index('o', -1)  # => 2
    'foo'.index('o', -2)  # => 1
    'foo'.index('o', -3)  # => 1
    'foo'.index('o', -4)  # => nil
    'foo'.index(/o./, -2) # => 1
    'foo'.index(/.o/, -2) # => 1

Related: `String#rindex`.

initialize_copy
Source
Also aliased as: replace
insert(index, other_string) → self
Source

    static VALUE
    rb_str_insert(VALUE str, VALUE idx, VALUE str2)
    {
        long pos = NUM2LONG(idx);

        if (pos == -1) {
            return rb_str_append(str, str2);
        }
        else if (pos < 0) {
            pos++;
        }
        rb_str_update(str, pos, 0, str2);
        return str;
    }

Inserts the given `other_string` into `self`; returns `self`.

If the `Integer` `index` is positive, inserts `other_string` at offset `index`:

    'foo'.insert(1, 'bar') # => "fbaroo"

If the `Integer` `index` is negative, counts backward from the end of `self` and inserts `other_string` at offset `index+1` (that is, after `self[index]`):

    'foo'.insert(-2, 'bar') # => "fobaro"

inspect → string
Source

    VALUE
    rb_str_inspect(VALUE str)
    {
        int encidx = ENCODING_GET(str);
        rb_encoding *enc = rb_enc_from_index(encidx);
        const char *p, *pend, *prev;
        char buf[CHAR_ESC_LEN + 1];
        VALUE result = rb_str_buf_new(0);
        rb_encoding *resenc = rb_default_internal_encoding();
        int unicode_p = rb_enc_unicode_p(enc);
        int asciicompat = rb_enc_asciicompat(enc);

        if (resenc == NULL) resenc = rb_default_external_encoding();
        if (!rb_enc_asciicompat(resenc)) resenc = rb_usascii_encoding();
        rb_enc_associate(result, resenc);
        str_buf_cat2(result, "\"");

        p = RSTRING_PTR(str); pend = RSTRING_END(str);
        prev = p;
        while (p < pend) {
            unsigned int c, cc;
            int n;

            n = rb_enc_precise_mbclen(p, pend, enc);
            if (!MBCLEN_CHARFOUND_P(n)) {
                if (p > prev) str_buf_cat(result, prev, p - prev);
                n = rb_enc_mbminlen(enc);
                if (pend < p + n)
                    n = (int)(pend - p);
                while (n--) {
                    snprintf(buf, CHAR_ESC_LEN, "\\x%02X", *p & 0377);
                    str_buf_cat(result, buf, strlen(buf));
                    prev = ++p;
                }
                continue;
            }
            n = MBCLEN_CHARFOUND_LEN(n);
            c = rb_enc_mbc_to_codepoint(p, pend, enc);
            p += n;
            if ((asciicompat || unicode_p) &&
              (c == '"'|| c == '\\' ||
                (c == '#' &&
                 p < pend &&
                 MBCLEN_CHARFOUND_P(rb_enc_precise_mbclen(p,pend,enc)) &&
                 (cc = rb_enc_codepoint(p,pend,enc),
                  (cc == '$' || cc == '@' || cc == '{'))))) {
                if (p - n > prev) str_buf_cat(result, prev, p - n - prev);
                str_buf_cat2(result, "\\");
                if (asciicompat || enc == resenc) {
                    prev = p - n;
                    continue;
                }
            }
            switch (c) {
              case '\n': cc = 'n'; break;
              case '\r': cc = 'r'; break;
              case '\t': cc = 't'; break;
              case '\f': cc = 'f'; break;
              case '\013': cc = 'v'; break;
              case '\010': cc = 'b'; break;
              case '\007': cc = 'a'; break;
              case 033: cc = 'e'; break;
              default: cc = 0; break;
            }
            if (cc) {
                if (p - n > prev) str_buf_cat(result, prev, p - n - prev);
                buf[0] = '\\';
                buf[1] = (char)cc;
                str_buf_cat(result, buf, 2);
                prev = p;
                continue;
            }
            /* The special casing of 0x85 (NEXT_LINE) here is because
             * Oniguruma historically treats it as printable, but it
             * doesn't match the print POSIX bracket class or character
             * property in regexps.
             *
             * See Ruby Bug #16842 for details:
             * https://bugs.ruby-lang.org/issues/16842
             */
            if ((enc == resenc && rb_enc_isprint(c, enc) && c != 0x85) ||
                (asciicompat && rb_enc_isascii(c, enc) && ISPRINT(c))) {
                continue;
            }
            else {
                if (p - n > prev) str_buf_cat(result, prev, p - n - prev);
                rb_str_buf_cat_escaped_char(result, c, unicode_p);
                prev = p;
                continue;
            }
        }
        if (p > prev) str_buf_cat(result, prev, p - prev);
        str_buf_cat2(result, "\"");

        return result;
    }

Returns a printable version of `self`, enclosed in double-quotes, and with special characters escaped:

    s = "foo\tbar\tbaz\n"
    s.inspect
    # => "\"foo\\tbar\\tbaz\\n\""

intern → symbol
Source

    VALUE
    rb_str_intern(VALUE str)
    {
        VALUE sym;

        GLOBAL_SYMBOLS_ENTER(symbols);
        {
            sym = lookup_str_sym_with_lock(symbols, str);

            if (sym) {
                // ok
            }
            else if (USE_SYMBOL_GC) {
                rb_encoding *enc = rb_enc_get(str);
                rb_encoding *ascii = rb_usascii_encoding();
                if (enc != ascii && sym_check_asciionly(str, false)) {
                    str = rb_str_dup(str);
                    rb_enc_associate(str, ascii);
                    OBJ_FREEZE(str);
                    enc = ascii;
                }
                else {
                    str = rb_str_dup(str);
                    OBJ_FREEZE(str);
                }
                str = rb_fstring(str);
                int type = rb_str_symname_type(str, IDSET_ATTRSET_FOR_INTERN);
                if (type < 0) type = ID_JUNK;
                sym = dsymbol_alloc(symbols, rb_cSymbol, str, enc, type);
            }
            else {
                ID id = intern_str(str, 0);
                sym = ID2SYM(id);
            }
        }
        GLOBAL_SYMBOLS_LEAVE();
        return sym;
    }

Returns the `Symbol` corresponding to str, creating the symbol if it did not previously exist. See `Symbol#id2name`.

    "Koala".intern         #=> :Koala
    s = 'cat'.to_sym       #=> :cat
    s == :cat              #=> true
    s = '@cat'.to_sym      #=> :@cat
    s == :@cat             #=> true

This can also be used to create symbols that cannot be represented using the `:xxx` notation.

    'cat and dog'.to_sym   #=> :"cat and dog"

Also aliased as: to_sym
length → integer
Source

    VALUE
    rb_str_length(VALUE str)
    {
        return LONG2NUM(str_strlen(str, NULL));
    }

Returns the count of characters (not bytes) in `self`:

    'foo'.length        # => 3
    'тест'.length       # => 4
    'こんにちは'.length   # => 5

Contrast with `String#bytesize`:

    'foo'.bytesize        # => 3
    'тест'.bytesize       # => 8
    'こんにちは'.bytesize   # => 15

Also aliased as: size
lines(Line_sep = $/, chomp: false) → array_of_strings
Source

    static VALUE
    rb_str_lines(int argc, VALUE *argv, VALUE str)
    {
        VALUE ary = WANTARRAY("lines", 0);
        return rb_str_enumerate_lines(argc, argv, str, ary);
    }

Forms substrings (“lines”) of `self` according to the given arguments (see `String#each_line` for details); returns the lines in an array.

ljust(size, pad_string = ' ') → new_string
Source

    static VALUE
    rb_str_ljust(int argc, VALUE *argv, VALUE str)
    {
        return rb_str_justify(argc, argv, str, 'l');
    }

Returns a left-justified copy of `self`.

If integer argument `size` is greater than the size (in characters) of `self`, returns a new string of length `size` that is a copy of `self`, left justified and padded on the right with `pad_string`:

    'hello'.ljust(10)       # => "hello     "
    '  hello'.ljust(10)     # => "  hello   "
    'hello'.ljust(10, 'ab') # => "helloababa"
    'тест'.ljust(10)        # => "тест      "
    'こんにちは'.ljust(10)    # => "こんにちは     "

If `size` is not greater than the size of `self`, returns a copy of `self`:

    'hello'.ljust(5)  # => "hello"
    'hello'.ljust(1)  # => "hello"

Related: `String#rjust`, `String#center`.

lstrip → new_string
Source

    static VALUE
    rb_str_lstrip(VALUE str)
    {
        char *start;
        long len, loffset;
        RSTRING_GETMEM(str, start, len);
        loffset = lstrip_offset(str, start, start+len, STR_ENC_GET(str));
        if (loffset <= 0) return str_duplicate(rb_cString, str);
        return rb_str_subseq(str, loffset, len - loffset);
    }

Returns a copy of `self` with leading whitespace removed; see Whitespace in Strings:

    whitespace = "\x00\t\n\v\f\r "
    s = whitespace + 'abc' + whitespace
    s        # => "\u0000\t\n\v\f\r abc\u0000\t\n\v\f\r "
    s.lstrip # => "abc\u0000\t\n\v\f\r "

Related: `String#rstrip`, `String#strip`.

lstrip! → self or nil
Source

    static VALUE
    rb_str_lstrip_bang(VALUE str)
    {
        rb_encoding *enc;
        char *start, *s;
        long olen, loffset;

        str_modify_keep_cr(str);
        enc = STR_ENC_GET(str);
        RSTRING_GETMEM(str, start, olen);
        loffset = lstrip_offset(str, start, start+olen, enc);
        if (loffset > 0) {
            long len = olen-loffset;
            s = start + loffset;
            memmove(start, s, len);
            STR_SET_LEN(str, len);
            TERM_FILL(start+len, rb_enc_mbminlen(enc));
            return str;
        }
        return Qnil;
    }

Like `String#lstrip`, except that any modifications are made in `self`; returns `self` if any modification are made, `nil` otherwise.

Related: `String#rstrip!`, `String#strip!`.

match(pattern, offset = 0) → matchdata or nil
match(pattern, offset = 0) {|matchdata| ... } → object
Source

    static VALUE
    rb_str_match_m(int argc, VALUE *argv, VALUE str)
    {
        VALUE re, result;
        if (argc < 1)
            rb_check_arity(argc, 1, 2);
        re = argv[0];
        argv[0] = str;
        result = rb_funcallv(get_pat(re), rb_intern("match"), argc, argv);
        if (!NIL_P(result) && rb_block_given_p()) {
            return rb_yield(result);
        }
        return result;
    }

Returns a `MatchData` object (or `nil`) based on `self` and the given `pattern`.

Note: also updates Global Variables at `Regexp`.

- Computes `regexp` by converting `pattern` (if not already a `Regexp`).

      regexp = Regexp.new(pattern)

- Computes `matchdata`, which will be either a `MatchData` object or `nil` (see `Regexp#match`):

      matchdata = <tt>regexp.match(self)

With no block given, returns the computed `matchdata`:

    'foo'.match('f') # => #<MatchData "f">
    'foo'.match('o') # => #<MatchData "o">
    'foo'.match('x') # => nil

If `Integer` argument `offset` is given, the search begins at index `offset`:

    'foo'.match('f', 1) # => nil
    'foo'.match('o', 1) # => #<MatchData "o">

With a block given, calls the block with the computed `matchdata` and returns the block’s return value:

    'foo'.match(/o/) {|matchdata| matchdata } # => #<MatchData "o">
    'foo'.match(/x/) {|matchdata| matchdata } # => nil
    'foo'.match(/f/, 1) {|matchdata| matchdata } # => nil

match?(pattern, offset = 0) → true or false
Source

    static VALUE
    rb_str_match_m_p(int argc, VALUE *argv, VALUE str)
    {
        VALUE re;
        rb_check_arity(argc, 1, 2);
        re = get_pat(argv[0]);
        return rb_reg_match_p(re, str, argc > 1 ? NUM2LONG(argv[1]) : 0);
    }

Returns `true` or `false` based on whether a match is found for `self` and `pattern`.

Note: does not update Global Variables at `Regexp`.

Computes `regexp` by converting `pattern` (if not already a `Regexp`).

    regexp = Regexp.new(pattern)

Returns `true` if `self+.match(regexp)` returns a `MatchData` object, `false` otherwise:

    'foo'.match?(/o/) # => true
    'foo'.match?('o') # => true
    'foo'.match?(/x/) # => false

If `Integer` argument `offset` is given, the search begins at index `offset`:

    'foo'.match?('f', 1) # => false
    'foo'.match?('o', 1) # => true

next
Alias for: succ
next!
Alias for: succ!
oct → integer
Source

    static VALUE
    rb_str_oct(VALUE str)
    {
        return rb_str_to_inum(str, -8, FALSE);
    }

Interprets the leading substring of `self` as a string of octal digits (with an optional sign) and returns the corresponding number; returns zero if there is no such leading substring:

    '123'.oct             # => 83
    '-377'.oct            # => -255
    '0377non-numeric'.oct # => 255
    'non-numeric'.oct     # => 0

If `self` starts with `0`, radix indicators are honored; see `Kernel#Integer`.

Related: `String#hex`.

ord → integer
Source

    static VALUE
    rb_str_ord(VALUE s)
    {
        unsigned int c;

        c = rb_enc_codepoint(RSTRING_PTR(s), RSTRING_END(s), STR_ENC_GET(s));
        return UINT2NUM(c);
    }

Returns the integer ordinal of the first character of `self`:

    'h'.ord         # => 104
    'hello'.ord     # => 104
    'тест'.ord      # => 1090
    'こんにちは'.ord  # => 12371

partition(string_or_regexp) → [head, match, tail]
Source

    static VALUE
    rb_str_partition(VALUE str, VALUE sep)
    {
        long pos;

        sep = get_pat_quoted(sep, 0);
        if (RB_TYPE_P(sep, T_REGEXP)) {
            if (rb_reg_search(sep, str, 0, 0) < 0) {
                goto failed;
            }
            VALUE match = rb_backref_get();
            struct re_registers *regs = RMATCH_REGS(match);

            pos = BEG(0);
            sep = rb_str_subseq(str, pos, END(0) - pos);
        }
        else {
            pos = rb_str_index(str, sep, 0);
            if (pos < 0) goto failed;
        }
        return rb_ary_new3(3, rb_str_subseq(str, 0, pos),
                              sep,
                              rb_str_subseq(str, pos+RSTRING_LEN(sep),
                                                 RSTRING_LEN(str)-pos-RSTRING_LEN(sep)));

      failed:
        return rb_ary_new3(3, str_duplicate(rb_cString, str), str_new_empty_String(str), str_new_empty_String(str));
    }

Returns a 3-element array of substrings of `self`.

Matches a pattern against `self`, scanning from the beginning. The pattern is:

- `string_or_regexp` itself, if it is a `Regexp`.

- `Regexp.quote(string_or_regexp)`, if `string_or_regexp` is a string.

If the pattern is matched, returns pre-match, first-match, post-match:

    'hello'.partition('l')      # => ["he", "l", "lo"]
    'hello'.partition('ll')     # => ["he", "ll", "o"]
    'hello'.partition('h')      # => ["", "h", "ello"]
    'hello'.partition('o')      # => ["hell", "o", ""]
    'hello'.partition(/l+/)     #=> ["he", "ll", "o"]
    'hello'.partition('')       # => ["", "", "hello"]
    'тест'.partition('т')       # => ["", "т", "ест"]
    'こんにちは'.partition('に')  # => ["こん", "に", "ちは"]

If the pattern is not matched, returns a copy of `self` and two empty strings:

    'hello'.partition('x') # => ["hello", "", ""]

Related: `String#rpartition`, `String#split`.

prepend(*other_strings) → string
Source

    static VALUE
    rb_str_prepend_multi(int argc, VALUE *argv, VALUE str)
    {
        str_modifiable(str);

        if (argc == 1) {
            rb_str_update(str, 0L, 0L, argv[0]);
        }
        else if (argc > 1) {
            int i;
            VALUE arg_str = rb_str_tmp_new(0);
            rb_enc_copy(arg_str, str);
            for (i = 0; i < argc; i++) {
                rb_str_append(arg_str, argv[i]);
            }
            rb_str_update(str, 0L, 0L, arg_str);
        }

        return str;
    }

Prepends each string in `other_strings` to `self` and returns `self`:

    s = 'foo'
    s.prepend('bar', 'baz') # => "barbazfoo"
    s                       # => "barbazfoo"

Related: `String#concat`.

replace(other_string) → self

Replaces the contents of `self` with the contents of `other_string`:

    s = 'foo'        # => "foo"
    s.replace('bar') # => "bar"

Alias for: initialize_copy
reverse → string
Source

    static VALUE
    rb_str_reverse(VALUE str)
    {
        rb_encoding *enc;
        VALUE rev;
        char *s, *e, *p;
        int cr;

        if (RSTRING_LEN(str) <= 1) return str_duplicate(rb_cString, str);
        enc = STR_ENC_GET(str);
        rev = rb_str_new(0, RSTRING_LEN(str));
        s = RSTRING_PTR(str); e = RSTRING_END(str);
        p = RSTRING_END(rev);
        cr = ENC_CODERANGE(str);

        if (RSTRING_LEN(str) > 1) {
            if (single_byte_optimizable(str)) {
                while (s < e) {
                    *--p = *s++;
                }
            }
            else if (cr == ENC_CODERANGE_VALID) {
                while (s < e) {
                    int clen = rb_enc_fast_mbclen(s, e, enc);

                    p -= clen;
                    memcpy(p, s, clen);
                    s += clen;
                }
            }
            else {
                cr = rb_enc_asciicompat(enc) ?
                    ENC_CODERANGE_7BIT : ENC_CODERANGE_VALID;
                while (s < e) {
                    int clen = rb_enc_mbclen(s, e, enc);

                    if (clen > 1 || (*s & 0x80)) cr = ENC_CODERANGE_UNKNOWN;
                    p -= clen;
                    memcpy(p, s, clen);
                    s += clen;
                }
            }
        }
        STR_SET_LEN(rev, RSTRING_LEN(str));
        str_enc_copy_direct(rev, str);
        ENC_CODERANGE_SET(rev, cr);

        return rev;
    }

Returns a new string with the characters from `self` in reverse order.

    'stressed'.reverse # => "desserts"

reverse! → self
Source

    static VALUE
    rb_str_reverse_bang(VALUE str)
    {
        if (RSTRING_LEN(str) > 1) {
            if (single_byte_optimizable(str)) {
                char *s, *e, c;

                str_modify_keep_cr(str);
                s = RSTRING_PTR(str);
                e = RSTRING_END(str) - 1;
                while (s < e) {
                    c = *s;
                    *s++ = *e;
                    *e-- = c;
                }
            }
            else {
                str_shared_replace(str, rb_str_reverse(str));
            }
        }
        else {
            str_modify_keep_cr(str);
        }
        return str;
    }

Returns `self` with its characters reversed:

    s = 'stressed'
    s.reverse! # => "desserts"
    s          # => "desserts"

rindex(substring, offset = self.length) → integer or nil
rindex(regexp, offset = self.length) → integer or nil
Source

    static VALUE
    rb_str_rindex_m(int argc, VALUE *argv, VALUE str)
    {
        VALUE sub;
        VALUE initpos;
        rb_encoding *enc = STR_ENC_GET(str);
        long pos, len = str_strlen(str, enc); /* str's enc */

        if (rb_scan_args(argc, argv, "11", &sub, &initpos) == 2) {
            pos = NUM2LONG(initpos);
            if (pos < 0 && (pos += len) < 0) {
                if (RB_TYPE_P(sub, T_REGEXP)) {
                    rb_backref_set(Qnil);
                }
                return Qnil;
            }
            if (pos > len) pos = len;
        }
        else {
            pos = len;
        }

        if (RB_TYPE_P(sub, T_REGEXP)) {
            /* enc = rb_enc_check(str, sub); */
            pos = str_offset(RSTRING_PTR(str), RSTRING_END(str), pos,
                             enc, single_byte_optimizable(str));

            if (rb_reg_search(sub, str, pos, 1) >= 0) {
                VALUE match = rb_backref_get();
                struct re_registers *regs = RMATCH_REGS(match);
                pos = rb_str_sublen(str, BEG(0));
                return LONG2NUM(pos);
            }
        }
        else {
            StringValue(sub);
            pos = rb_str_rindex(str, sub, pos);
            if (pos >= 0) {
                pos = rb_str_sublen(str, pos);
                return LONG2NUM(pos);
            }
        }
        return Qnil;
    }

Returns the `Integer` index of the last occurrence of the given `substring`, or `nil` if none found:

    'foo'.rindex('f') # => 0
    'foo'.rindex('o') # => 2
    'foo'.rindex('oo') # => 1
    'foo'.rindex('ooo') # => nil

Returns the `Integer` index of the last match for the given `Regexp` `regexp`, or `nil` if none found:

    'foo'.rindex(/f/) # => 0
    'foo'.rindex(/o/) # => 2
    'foo'.rindex(/oo/) # => 1
    'foo'.rindex(/ooo/) # => nil

The last match means starting at the possible last position, not the last of longest matches.

    'foo'.rindex(/o+/) # => 2
    $~ #=> #<MatchData "o">

To get the last longest match, needs to combine with negative lookbehind.

    'foo'.rindex(/(?<!o)o+/) # => 1
    $~ #=> #<MatchData "oo">

Or `String#index` with negative lookforward.

    'foo'.index(/o+(?!.*o)/) # => 1
    $~ #=> #<MatchData "oo">

`Integer` argument `offset`, if given and non-negative, specifies the maximum starting position in the string to end the search:

    'foo'.rindex('o', 0) # => nil
    'foo'.rindex('o', 1) # => 1
    'foo'.rindex('o', 2) # => 2
    'foo'.rindex('o', 3) # => 2

If `offset` is a negative `Integer`, the maximum starting position in the string to end the search is the sum of the string’s length and `offset`:

    'foo'.rindex('o', -1) # => 2
    'foo'.rindex('o', -2) # => 1
    'foo'.rindex('o', -3) # => nil
    'foo'.rindex('o', -4) # => nil

Related: `String#index`.

rjust(size, pad_string = ' ') → new_string
Source

    static VALUE
    rb_str_rjust(int argc, VALUE *argv, VALUE str)
    {
        return rb_str_justify(argc, argv, str, 'r');
    }

Returns a right-justified copy of `self`.

If integer argument `size` is greater than the size (in characters) of `self`, returns a new string of length `size` that is a copy of `self`, right justified and padded on the left with `pad_string`:

    'hello'.rjust(10)       # => "     hello"
    'hello  '.rjust(10)     # => "   hello  "
    'hello'.rjust(10, 'ab') # => "ababahello"
    'тест'.rjust(10)        # => "      тест"
    'こんにちは'.rjust(10)    # => "     こんにちは"

If `size` is not greater than the size of `self`, returns a copy of `self`:

    'hello'.rjust(5, 'ab')  # => "hello"
    'hello'.rjust(1, 'ab')  # => "hello"

Related: `String#ljust`, `String#center`.

rpartition(sep) → [head, match, tail]
Source

    static VALUE
    rb_str_rpartition(VALUE str, VALUE sep)
    {
        long pos = RSTRING_LEN(str);

        sep = get_pat_quoted(sep, 0);
        if (RB_TYPE_P(sep, T_REGEXP)) {
            if (rb_reg_search(sep, str, pos, 1) < 0) {
                goto failed;
            }
            VALUE match = rb_backref_get();
            struct re_registers *regs = RMATCH_REGS(match);

            pos = BEG(0);
            sep = rb_str_subseq(str, pos, END(0) - pos);
        }
        else {
            pos = rb_str_sublen(str, pos);
            pos = rb_str_rindex(str, sep, pos);
            if (pos < 0) {
                goto failed;
            }
        }

        return rb_ary_new3(3, rb_str_subseq(str, 0, pos),
                              sep,
                              rb_str_subseq(str, pos+RSTRING_LEN(sep),
                                            RSTRING_LEN(str)-pos-RSTRING_LEN(sep)));
      failed:
        return rb_ary_new3(3, str_new_empty_String(str), str_new_empty_String(str), str_duplicate(rb_cString, str));
    }

Returns a 3-element array of substrings of `self`.

Matches a pattern against `self`, scanning backwards from the end. The pattern is:

- `string_or_regexp` itself, if it is a `Regexp`.

- `Regexp.quote(string_or_regexp)`, if `string_or_regexp` is a string.

If the pattern is matched, returns pre-match, last-match, post-match:

    'hello'.rpartition('l')      # => ["hel", "l", "o"]
    'hello'.rpartition('ll')     # => ["he", "ll", "o"]
    'hello'.rpartition('h')      # => ["", "h", "ello"]
    'hello'.rpartition('o')      # => ["hell", "o", ""]
    'hello'.rpartition(/l+/)     # => ["hel", "l", "o"]
    'hello'.rpartition('')       # => ["hello", "", ""]
    'тест'.rpartition('т')       # => ["тес", "т", ""]
    'こんにちは'.rpartition('に')  # => ["こん", "に", "ちは"]

If the pattern is not matched, returns two empty strings and a copy of `self`:

    'hello'.rpartition('x') # => ["", "", "hello"]

Related: `String#partition`, `String#split`.

rstrip → new_string
Source

    static VALUE
    rb_str_rstrip(VALUE str)
    {
        rb_encoding *enc;
        char *start;
        long olen, roffset;

        enc = STR_ENC_GET(str);
        RSTRING_GETMEM(str, start, olen);
        roffset = rstrip_offset(str, start, start+olen, enc);

        if (roffset <= 0) return str_duplicate(rb_cString, str);
        return rb_str_subseq(str, 0, olen-roffset);
    }

Returns a copy of the receiver with trailing whitespace removed; see Whitespace in Strings:

    whitespace = "\x00\t\n\v\f\r "
    s = whitespace + 'abc' + whitespace
    s        # => "\u0000\t\n\v\f\r abc\u0000\t\n\v\f\r "
    s.rstrip # => "\u0000\t\n\v\f\r abc"

Related: `String#lstrip`, `String#strip`.

rstrip! → self or nil
Source

    static VALUE
    rb_str_rstrip_bang(VALUE str)
    {
        rb_encoding *enc;
        char *start;
        long olen, roffset;

        str_modify_keep_cr(str);
        enc = STR_ENC_GET(str);
        RSTRING_GETMEM(str, start, olen);
        roffset = rstrip_offset(str, start, start+olen, enc);
        if (roffset > 0) {
            long len = olen - roffset;

            STR_SET_LEN(str, len);
            TERM_FILL(start+len, rb_enc_mbminlen(enc));
            return str;
        }
        return Qnil;
    }

Like `String#rstrip`, except that any modifications are made in `self`; returns `self` if any modification are made, `nil` otherwise.

Related: `String#lstrip!`, `String#strip!`.

scan(string_or_regexp) → array
scan(string_or_regexp) {|matches| ... } → self
Source

    static VALUE
    rb_str_scan(VALUE str, VALUE pat)
    {
        VALUE result;
        long start = 0;
        long last = -1, prev = 0;
        char *p = RSTRING_PTR(str); long len = RSTRING_LEN(str);

        pat = get_pat_quoted(pat, 1);
        mustnot_broken(str);
        if (!rb_block_given_p()) {
            VALUE ary = rb_ary_new();

            while (!NIL_P(result = scan_once(str, pat, &start, 0))) {
                last = prev;
                prev = start;
                rb_ary_push(ary, result);
            }
            if (last >= 0) rb_pat_search(pat, str, last, 1);
            else rb_backref_set(Qnil);
            return ary;
        }

        while (!NIL_P(result = scan_once(str, pat, &start, 1))) {
            last = prev;
            prev = start;
            rb_yield(result);
            str_mod_check(str, p, len);
        }
        if (last >= 0) rb_pat_search(pat, str, last, 1);
        return str;
    }

Matches a pattern against `self`; the pattern is:

- `string_or_regexp` itself, if it is a `Regexp`.

- `Regexp.quote(string_or_regexp)`, if `string_or_regexp` is a string.

Iterates through `self`, generating a collection of matching results:

- If the pattern contains no groups, each result is the matched string, `$&`.

- If the pattern contains groups, each result is an array containing one entry per group.

With no block given, returns an array of the results:

    s = 'cruel world'
    s.scan(/\w+/)      # => ["cruel", "world"]
    s.scan(/.../)      # => ["cru", "el ", "wor"]
    s.scan(/(...)/)    # => [["cru"], ["el "], ["wor"]]
    s.scan(/(..)(..)/) # => [["cr", "ue"], ["l ", "wo"]]

With a block given, calls the block with each result; returns `self`:

    s.scan(/\w+/) {|w| print "<<#{w}>> " }
    print "\n"
    s.scan(/(.)(.)/) {|x,y| print y, x }
    print "\n"

Output:

    <<cruel>> <<world>>
    rceu lowlr

scrub(replacement_string = default_replacement) → new_string
scrub{|bytes| ... } → new_string
Source

    static VALUE
    str_scrub(int argc, VALUE *argv, VALUE str)
    {
        VALUE repl = argc ? (rb_check_arity(argc, 0, 1), argv[0]) : Qnil;
        VALUE new = rb_str_scrub(str, repl);
        return NIL_P(new) ? str_duplicate(rb_cString, str): new;
    }

Returns a copy of `self` with each invalid byte sequence replaced by the given `replacement_string`.

With no block given and no argument, replaces each invalid sequence with the default replacement string (`"�"` for a Unicode encoding, `'?'` otherwise):

    s = "foo\x81\x81bar"
    s.scrub # => "foo��bar"

With no block given and argument `replacement_string` given, replaces each invalid sequence with that string:

    "foo\x81\x81bar".scrub('xyzzy') # => "fooxyzzyxyzzybar"

With a block given, replaces each invalid sequence with the value of the block:

    "foo\x81\x81bar".scrub {|bytes| p bytes; 'XYZZY' }
    # => "fooXYZZYXYZZYbar"

Output:

    "\x81"
    "\x81"

scrub! → self
scrub!(replacement_string = default_replacement) → self
scrub!{|bytes| ... } → self
Source

    static VALUE
    str_scrub_bang(int argc, VALUE *argv, VALUE str)
    {
        VALUE repl = argc ? (rb_check_arity(argc, 0, 1), argv[0]) : Qnil;
        VALUE new = rb_str_scrub(str, repl);
        if (!NIL_P(new)) rb_str_replace(str, new);
        return str;
    }

Like `String#scrub`, except that any replacements are made in `self`.

setbyte(index, integer) → integer
Source

    VALUE
    rb_str_setbyte(VALUE str, VALUE index, VALUE value)
    {
        long pos = NUM2LONG(index);
        long len = RSTRING_LEN(str);
        char *ptr, *head, *left = 0;
        rb_encoding *enc;
        int cr = ENC_CODERANGE_UNKNOWN, width, nlen;

        if (pos < -len || len <= pos)
            rb_raise(rb_eIndexError, "index %ld out of string", pos);
        if (pos < 0)
            pos += len;

        VALUE v = rb_to_int(value);
        VALUE w = rb_int_and(v, INT2FIX(0xff));
        char byte = (char)(NUM2INT(w) & 0xFF);

        if (!str_independent(str))
            str_make_independent(str);
        enc = STR_ENC_GET(str);
        head = RSTRING_PTR(str);
        ptr = &head[pos];
        if (!STR_EMBED_P(str)) {
            cr = ENC_CODERANGE(str);
            switch (cr) {
              case ENC_CODERANGE_7BIT:
                left = ptr;
                *ptr = byte;
                if (ISASCII(byte)) goto end;
                nlen = rb_enc_precise_mbclen(left, head+len, enc);
                if (!MBCLEN_CHARFOUND_P(nlen))
                    ENC_CODERANGE_SET(str, ENC_CODERANGE_BROKEN);
                else
                    ENC_CODERANGE_SET(str, ENC_CODERANGE_VALID);
                goto end;
              case ENC_CODERANGE_VALID:
                left = rb_enc_left_char_head(head, ptr, head+len, enc);
                width = rb_enc_precise_mbclen(left, head+len, enc);
                *ptr = byte;
                nlen = rb_enc_precise_mbclen(left, head+len, enc);
                if (!MBCLEN_CHARFOUND_P(nlen))
                    ENC_CODERANGE_SET(str, ENC_CODERANGE_BROKEN);
                else if (MBCLEN_CHARFOUND_LEN(nlen) != width || ISASCII(byte))
                    ENC_CODERANGE_CLEAR(str);
                goto end;
            }
        }
        ENC_CODERANGE_CLEAR(str);
        *ptr = byte;

      end:
        return value;
    }

Sets the byte at zero-based `index` to `integer`; returns `integer`:

    s = 'abcde'      # => "abcde"
    s.setbyte(0, 98) # => 98
    s                # => "bbcde"

Related: `String#getbyte`.

shellescape → string
Source

    # File lib/shellwords.rb, line 238
    def shellescape
      Shellwords.escape(self)
    end

Escapes `str` so that it can be safely used in a Bourne shell command line.

See `Shellwords.shellescape` for details.

shellsplit → array
Source

    # File lib/shellwords.rb, line 227
    def shellsplit
      Shellwords.split(self)
    end

Splits `str` into an array of tokens in the same way the UNIX Bourne shell does.

See `Shellwords.shellsplit` for details.

size
Alias for: length
slice
Alias for: []
slice!(index) → new_string or nil
slice!(start, length) → new_string or nil
slice!(range) → new_string or nil
slice!(regexp, capture = 0) → new_string or nil
slice!(substring) → new_string or nil
Source

    static VALUE
    rb_str_slice_bang(int argc, VALUE *argv, VALUE str)
    {
        VALUE result = Qnil;
        VALUE indx;
        long beg, len = 1;
        char *p;

        rb_check_arity(argc, 1, 2);
        str_modify_keep_cr(str);
        indx = argv[0];
        if (RB_TYPE_P(indx, T_REGEXP)) {
            if (rb_reg_search(indx, str, 0, 0) < 0) return Qnil;
            VALUE match = rb_backref_get();
            struct re_registers *regs = RMATCH_REGS(match);
            int nth = 0;
            if (argc > 1 && (nth = rb_reg_backref_number(match, argv[1])) < 0) {
                if ((nth += regs->num_regs) <= 0) return Qnil;
            }
            else if (nth >= regs->num_regs) return Qnil;
            beg = BEG(nth);
            len = END(nth) - beg;
            goto subseq;
        }
        else if (argc == 2) {
            beg = NUM2LONG(indx);
            len = NUM2LONG(argv[1]);
            goto num_index;
        }
        else if (FIXNUM_P(indx)) {
            beg = FIX2LONG(indx);
            if (!(p = rb_str_subpos(str, beg, &len))) return Qnil;
            if (!len) return Qnil;
            beg = p - RSTRING_PTR(str);
            goto subseq;
        }
        else if (RB_TYPE_P(indx, T_STRING)) {
            beg = rb_str_index(str, indx, 0);
            if (beg == -1) return Qnil;
            len = RSTRING_LEN(indx);
            result = str_duplicate(rb_cString, indx);
            goto squash;
        }
        else {
            switch (rb_range_beg_len(indx, &beg, &len, str_strlen(str, NULL), 0)) {
              case Qnil:
                return Qnil;
              case Qfalse:
                beg = NUM2LONG(indx);
                if (!(p = rb_str_subpos(str, beg, &len))) return Qnil;
                if (!len) return Qnil;
                beg = p - RSTRING_PTR(str);
                goto subseq;
              default:
                goto num_index;
            }
        }

      num_index:
        if (!(p = rb_str_subpos(str, beg, &len))) return Qnil;
        beg = p - RSTRING_PTR(str);

      subseq:
        result = rb_str_new(RSTRING_PTR(str)+beg, len);
        rb_enc_cr_str_copy_for_substr(result, str);

      squash:
        if (len > 0) {
            if (beg == 0) {
                rb_str_drop_bytes(str, len);
            }
            else {
                char *sptr = RSTRING_PTR(str);
                long slen = RSTRING_LEN(str);
                if (beg + len > slen) /* pathological check */
                    len = slen - beg;
                memmove(sptr + beg,
                        sptr + beg + len,
                        slen - (beg + len));
                slen -= len;
                STR_SET_LEN(str, slen);
                TERM_FILL(&sptr[slen], TERM_LEN(str));
            }
        }
        return result;
    }

Removes and returns the substring of `self` specified by the arguments. See String Slices.

A few examples:

    string = "This is a string"
    string.slice!(2)        #=> "i"
    string.slice!(3..6)     #=> " is "
    string.slice!(/s.*t/)   #=> "sa st"
    string.slice!("r")      #=> "r"
    string                  #=> "Thing"

split(field_sep = $;, limit = 0) → array
split(field_sep = $;, limit = 0) {|substring| ... } → self
Source

    static VALUE
    rb_str_split_m(int argc, VALUE *argv, VALUE str)
    {
        rb_encoding *enc;
        VALUE spat;
        VALUE limit;
        split_type_t split_type;
        long beg, end, i = 0, empty_count = -1;
        int lim = 0;
        VALUE result, tmp;

        result = rb_block_given_p() ? Qfalse : Qnil;
        if (rb_scan_args(argc, argv, "02", &spat, &limit) == 2) {
            lim = NUM2INT(limit);
            if (lim <= 0) limit = Qnil;
            else if (lim == 1) {
                if (RSTRING_LEN(str) == 0)
                    return result ? rb_ary_new2(0) : str;
                tmp = str_duplicate(rb_cString, str);
                if (!result) {
                    rb_yield(tmp);
                    return str;
                }
                return rb_ary_new3(1, tmp);
            }
            i = 1;
        }
        if (NIL_P(limit) && !lim) empty_count = 0;

        enc = STR_ENC_GET(str);
        split_type = SPLIT_TYPE_REGEXP;
        if (!NIL_P(spat)) {
            spat = get_pat_quoted(spat, 0);
        }
        else if (NIL_P(spat = rb_fs)) {
            split_type = SPLIT_TYPE_AWK;
        }
        else if (!(spat = rb_fs_check(spat))) {
            rb_raise(rb_eTypeError, "value of $; must be String or Regexp");
        }
        else {
            rb_category_warn(RB_WARN_CATEGORY_DEPRECATED, "$; is set to non-nil value");
        }
        if (split_type != SPLIT_TYPE_AWK) {
            switch (BUILTIN_TYPE(spat)) {
              case T_REGEXP:
                rb_reg_options(spat); /* check if uninitialized */
                tmp = RREGEXP_SRC(spat);
                split_type = literal_split_pattern(tmp, SPLIT_TYPE_REGEXP);
                if (split_type == SPLIT_TYPE_AWK) {
                    spat = tmp;
                    split_type = SPLIT_TYPE_STRING;
                }
                break;

              case T_STRING:
                mustnot_broken(spat);
                split_type = literal_split_pattern(spat, SPLIT_TYPE_STRING);
                break;

              default:
                UNREACHABLE_RETURN(Qnil);
            }
        }

    #define SPLIT_STR(beg, len) (empty_count = split_string(result, str, beg, len, empty_count))

        beg = 0;
        char *ptr = RSTRING_PTR(str);
        char *eptr = RSTRING_END(str);
        if (split_type == SPLIT_TYPE_AWK) {
            char *bptr = ptr;
            int skip = 1;
            unsigned int c;

            if (result) result = rb_ary_new();
            end = beg;
            if (is_ascii_string(str)) {
                while (ptr < eptr) {
                    c = (unsigned char)*ptr++;
                    if (skip) {
                        if (ascii_isspace(c)) {
                            beg = ptr - bptr;
                        }
                        else {
                            end = ptr - bptr;
                            skip = 0;
                            if (!NIL_P(limit) && lim <= i) break;
                        }
                    }
                    else if (ascii_isspace(c)) {
                        SPLIT_STR(beg, end-beg);
                        skip = 1;
                        beg = ptr - bptr;
                        if (!NIL_P(limit)) ++i;
                    }
                    else {
                        end = ptr - bptr;
                    }
                }
            }
            else {
                while (ptr < eptr) {
                    int n;

                    c = rb_enc_codepoint_len(ptr, eptr, &n, enc);
                    ptr += n;
                    if (skip) {
                        if (rb_isspace(c)) {
                            beg = ptr - bptr;
                        }
                        else {
                            end = ptr - bptr;
                            skip = 0;
                            if (!NIL_P(limit) && lim <= i) break;
                        }
                    }
                    else if (rb_isspace(c)) {
                        SPLIT_STR(beg, end-beg);
                        skip = 1;
                        beg = ptr - bptr;
                        if (!NIL_P(limit)) ++i;
                    }
                    else {
                        end = ptr - bptr;
                    }
                }
            }
        }
        else if (split_type == SPLIT_TYPE_STRING) {
            char *str_start = ptr;
            char *substr_start = ptr;
            char *sptr = RSTRING_PTR(spat);
            long slen = RSTRING_LEN(spat);

            if (result) result = rb_ary_new();
            mustnot_broken(str);
            enc = rb_enc_check(str, spat);
            while (ptr < eptr &&
                   (end = rb_memsearch(sptr, slen, ptr, eptr - ptr, enc)) >= 0) {
                /* Check we are at the start of a char */
                char *t = rb_enc_right_char_head(ptr, ptr + end, eptr, enc);
                if (t != ptr + end) {
                    ptr = t;
                    continue;
                }
                SPLIT_STR(substr_start - str_start, (ptr+end) - substr_start);
                ptr += end + slen;
                substr_start = ptr;
                if (!NIL_P(limit) && lim <= ++i) break;
            }
            beg = ptr - str_start;
        }
        else if (split_type == SPLIT_TYPE_CHARS) {
            char *str_start = ptr;
            int n;

            if (result) result = rb_ary_new_capa(RSTRING_LEN(str));
            mustnot_broken(str);
            enc = rb_enc_get(str);
            while (ptr < eptr &&
                   (n = rb_enc_precise_mbclen(ptr, eptr, enc)) > 0) {
                SPLIT_STR(ptr - str_start, n);
                ptr += n;
                if (!NIL_P(limit) && lim <= ++i) break;
            }
            beg = ptr - str_start;
        }
        else {
            if (result) result = rb_ary_new();
            long len = RSTRING_LEN(str);
            long start = beg;
            long idx;
            int last_null = 0;
            struct re_registers *regs;
            VALUE match = 0;

            for (; rb_reg_search(spat, str, start, 0) >= 0;
                 (match ? (rb_match_unbusy(match), rb_backref_set(match)) : (void)0)) {
                match = rb_backref_get();
                if (!result) rb_match_busy(match);
                regs = RMATCH_REGS(match);
                end = BEG(0);
                if (start == end && BEG(0) == END(0)) {
                    if (!ptr) {
                        SPLIT_STR(0, 0);
                        break;
                    }
                    else if (last_null == 1) {
                        SPLIT_STR(beg, rb_enc_fast_mbclen(ptr+beg, eptr, enc));
                        beg = start;
                    }
                    else {
                        if (start == len)
                            start++;
                        else
                            start += rb_enc_fast_mbclen(ptr+start,eptr,enc);
                        last_null = 1;
                        continue;
                    }
                }
                else {
                    SPLIT_STR(beg, end-beg);
                    beg = start = END(0);
                }
                last_null = 0;

                for (idx=1; idx < regs->num_regs; idx++) {
                    if (BEG(idx) == -1) continue;
                    SPLIT_STR(BEG(idx), END(idx)-BEG(idx));
                }
                if (!NIL_P(limit) && lim <= ++i) break;
            }
            if (match) rb_match_unbusy(match);
        }
        if (RSTRING_LEN(str) > 0 && (!NIL_P(limit) || RSTRING_LEN(str) > beg || lim < 0)) {
            SPLIT_STR(beg, RSTRING_LEN(str)-beg);
        }

        return result ? result : str;
    }

Returns an array of substrings of `self` that are the result of splitting `self` at each occurrence of the given field separator `field_sep`.

When `field_sep` is `$;`:

- If `$;` is `nil` (its default value), the split occurs just as if `field_sep` were given as a space character (see below).

- If `$;` is a string, the split occurs just as if `field_sep` were given as that string (see below).

When `field_sep` is `' '` and `limit` is `0` (its default value), the split occurs at each sequence of whitespace:

    'abc def ghi'.split(' ')         => ["abc", "def", "ghi"]
    "abc \n\tdef\t\n  ghi".split(' ') # => ["abc", "def", "ghi"]
    'abc  def   ghi'.split(' ')      => ["abc", "def", "ghi"]
    ''.split(' ')                    => []

When `field_sep` is a string different from `' '` and `limit` is `0`, the split occurs at each occurrence of `field_sep`; trailing empty substrings are not returned:

    'abracadabra'.split('ab')  => ["", "racad", "ra"]
    'aaabcdaaa'.split('a')     => ["", "", "", "bcd"]
    ''.split('a')              => []
    '3.14159'.split('1')       => ["3.", "4", "59"]
    '!@#$%^$&*($)_+'.split('$') # => ["!@#", "%^", "&*(", ")_+"]
    'тест'.split('т')          => ["", "ес"]
    'こんにちは'.split('に')     => ["こん", "ちは"]

When `field_sep` is a `Regexp` and `limit` is `0`, the split occurs at each occurrence of a match; trailing empty substrings are not returned:

    'abracadabra'.split(/ab/) # => ["", "racad", "ra"]
    'aaabcdaaa'.split(/a/)   => ["", "", "", "bcd"]
    'aaabcdaaa'.split(//)    => ["a", "a", "a", "b", "c", "d", "a", "a", "a"]
    '1 + 1 == 2'.split(/\W+/) # => ["1", "1", "2"]

If the Regexp contains groups, their matches are also included in the returned array:

    '1:2:3'.split(/(:)()()/, 2) # => ["1", ":", "", "", "2:3"]

As seen above, if `limit` is `0`, trailing empty substrings are not returned:

    'aaabcdaaa'.split('a')   => ["", "", "", "bcd"]

If `limit` is positive integer `n`, no more than `n - 1-` splits occur, so that at most `n` substrings are returned, and trailing empty substrings are included:

    'aaabcdaaa'.split('a', 1) # => ["aaabcdaaa"]
    'aaabcdaaa'.split('a', 2) # => ["", "aabcdaaa"]
    'aaabcdaaa'.split('a', 5) # => ["", "", "", "bcd", "aa"]
    'aaabcdaaa'.split('a', 7) # => ["", "", "", "bcd", "", "", ""]
    'aaabcdaaa'.split('a', 8) # => ["", "", "", "bcd", "", "", ""]

Note that if `field_sep` is a Regexp containing groups, their matches are in the returned array, but do not count toward the limit.

If `limit` is negative, it behaves the same as if `limit` was zero, meaning that there is no limit, and trailing empty substrings are included:

    'aaabcdaaa'.split('a', -1) # => ["", "", "", "bcd", "", "", ""]

If a block is given, it is called with each substring:

    'abc def ghi'.split(' ') {|substring| p substring }

Output:

    "abc"
    "def"
    "ghi"

Related: `String#partition`, `String#rpartition`.

squeeze(*selectors) → new_string
Source

    static VALUE
    rb_str_squeeze(int argc, VALUE *argv, VALUE str)
    {
        str = str_duplicate(rb_cString, str);
        rb_str_squeeze_bang(argc, argv, str);
        return str;
    }

Returns a copy of `self` with characters specified by `selectors` “squeezed” (see Multiple Character Selectors):

“Squeezed” means that each multiple-character run of a selected character is squeezed down to a single character; with no arguments given, squeezes all characters:

    "yellow moon".squeeze                  #=> "yelow mon"
    "  now   is  the".squeeze(" ")         #=> " now is the"
    "putters shoot balls".squeeze("m-z")   #=> "puters shot balls"

squeeze!(*selectors) → self or nil
Source

    static VALUE
    rb_str_squeeze_bang(int argc, VALUE *argv, VALUE str)
    {
        char squeez[TR_TABLE_SIZE];
        rb_encoding *enc = 0;
        VALUE del = 0, nodel = 0;
        unsigned char *s, *send, *t;
        int i, modify = 0;
        int ascompat, singlebyte = single_byte_optimizable(str);
        unsigned int save;

        if (argc == 0) {
            enc = STR_ENC_GET(str);
        }
        else {
            for (i=0; i<argc; i++) {
                VALUE s = argv[i];

                StringValue(s);
                enc = rb_enc_check(str, s);
                if (singlebyte && !single_byte_optimizable(s))
                    singlebyte = 0;
                tr_setup_table(s, squeez, i==0, &del, &nodel, enc);
            }
        }

        str_modify_keep_cr(str);
        s = t = (unsigned char *)RSTRING_PTR(str);
        if (!s || RSTRING_LEN(str) == 0) return Qnil;
        send = (unsigned char *)RSTRING_END(str);
        save = -1;
        ascompat = rb_enc_asciicompat(enc);

        if (singlebyte) {
            while (s < send) {
                unsigned int c = *s++;
                if (c != save || (argc > 0 && !squeez[c])) {
                    *t++ = save = c;
                }
            }
        }
        else {
            while (s < send) {
                unsigned int c;
                int clen;

                if (ascompat && (c = *s) < 0x80) {
                    if (c != save || (argc > 0 && !squeez[c])) {
                        *t++ = save = c;
                    }
                    s++;
                }
                else {
                    c = rb_enc_codepoint_len((char *)s, (char *)send, &clen, enc);

                    if (c != save || (argc > 0 && !tr_find(c, squeez, del, nodel))) {
                        if (t != s) rb_enc_mbcput(c, t, enc);
                        save = c;
                        t += clen;
                    }
                    s += clen;
                }
            }
        }

        TERM_FILL((char *)t, TERM_LEN(str));
        if ((char *)t - RSTRING_PTR(str) != RSTRING_LEN(str)) {
            STR_SET_LEN(str, (char *)t - RSTRING_PTR(str));
            modify = 1;
        }

        if (modify) return str;
        return Qnil;
    }

Like `String#squeeze`, but modifies `self` in place. Returns `self` if any changes were made, `nil` otherwise.

start_with?(*string_or_regexp) → true or false
Source

    static VALUE
    rb_str_start_with(int argc, VALUE *argv, VALUE str)
    {
        int i;

        for (i=0; i<argc; i++) {
            VALUE tmp = argv[i];
            if (RB_TYPE_P(tmp, T_REGEXP)) {
                if (rb_reg_start_with_p(tmp, str))
                    return Qtrue;
            }
            else {
                const char *p, *s, *e;
                long slen, tlen;
                rb_encoding *enc;

                StringValue(tmp);
                enc = rb_enc_check(str, tmp);
                if ((tlen = RSTRING_LEN(tmp)) == 0) return Qtrue;
                if ((slen = RSTRING_LEN(str)) < tlen) continue;
                p = RSTRING_PTR(str);
                e = p + slen;
                s = p + tlen;
                if (!at_char_right_boundary(p, s, e, enc))
                    continue;
                if (memcmp(p, RSTRING_PTR(tmp), tlen) == 0)
                    return Qtrue;
            }
        }
        return Qfalse;
    }

Returns whether `self` starts with any of the given `string_or_regexp`.

Matches patterns against the beginning of `self`. For each given `string_or_regexp`, the pattern is:

- `string_or_regexp` itself, if it is a `Regexp`.

- `Regexp.quote(string_or_regexp)`, if `string_or_regexp` is a string.

Returns `true` if any pattern matches the beginning, `false` otherwise:

    'hello'.start_with?('hell')               # => true
    'hello'.start_with?(/H/i)                 # => true
    'hello'.start_with?('heaven', 'hell')     # => true
    'hello'.start_with?('heaven', 'paradise') # => false
    'тест'.start_with?('т')                   # => true
    'こんにちは'.start_with?('こ')              # => true

Related: `String#end_with?`.

strip → new_string
Source

    static VALUE
    rb_str_strip(VALUE str)
    {
        char *start;
        long olen, loffset, roffset;
        rb_encoding *enc = STR_ENC_GET(str);

        RSTRING_GETMEM(str, start, olen);
        loffset = lstrip_offset(str, start, start+olen, enc);
        roffset = rstrip_offset(str, start+loffset, start+olen, enc);

        if (loffset <= 0 && roffset <= 0) return str_duplicate(rb_cString, str);
        return rb_str_subseq(str, loffset, olen-loffset-roffset);
    }

Returns a copy of the receiver with leading and trailing whitespace removed; see Whitespace in Strings:

    whitespace = "\x00\t\n\v\f\r "
    s = whitespace + 'abc' + whitespace
    s       # => "\u0000\t\n\v\f\r abc\u0000\t\n\v\f\r "
    s.strip # => "abc"

Related: `String#lstrip`, `String#rstrip`.

strip! → self or nil
Source

    static VALUE
    rb_str_strip_bang(VALUE str)
    {
        char *start;
        long olen, loffset, roffset;
        rb_encoding *enc;

        str_modify_keep_cr(str);
        enc = STR_ENC_GET(str);
        RSTRING_GETMEM(str, start, olen);
        loffset = lstrip_offset(str, start, start+olen, enc);
        roffset = rstrip_offset(str, start+loffset, start+olen, enc);

        if (loffset > 0 || roffset > 0) {
            long len = olen-roffset;
            if (loffset > 0) {
                len -= loffset;
                memmove(start, start + loffset, len);
            }
            STR_SET_LEN(str, len);
            TERM_FILL(start+len, rb_enc_mbminlen(enc));
            return str;
        }
        return Qnil;
    }

Like `String#strip`, except that any modifications are made in `self`; returns `self` if any modification are made, `nil` otherwise.

Related: `String#lstrip!`, `String#strip!`.

sub(pattern, replacement) → new_string
sub(pattern) {|match| ... } → new_string
Source

    static VALUE
    rb_str_sub(int argc, VALUE *argv, VALUE str)
    {
        str = str_duplicate(rb_cString, str);
        rb_str_sub_bang(argc, argv, str);
        return str;
    }

Returns a copy of `self` with only the first occurrence (not all occurrences) of the given `pattern` replaced.

See Substitution Methods.

Related: `String#sub!`, `String#gsub`, `String#gsub!`.

sub!(pattern, replacement) → self or nil
sub!(pattern) {|match| ... } → self or nil
Source

    static VALUE
    rb_str_sub_bang(int argc, VALUE *argv, VALUE str)
    {
        VALUE pat, repl, hash = Qnil;
        int iter = 0;
        long plen;
        int min_arity = rb_block_given_p() ? 1 : 2;
        long beg;

        rb_check_arity(argc, min_arity, 2);
        if (argc == 1) {
            iter = 1;
        }
        else {
            repl = argv[1];
            hash = rb_check_hash_type(argv[1]);
            if (NIL_P(hash)) {
                StringValue(repl);
            }
        }

        pat = get_pat_quoted(argv[0], 1);

        str_modifiable(str);
        beg = rb_pat_search(pat, str, 0, 1);
        if (beg >= 0) {
            rb_encoding *enc;
            int cr = ENC_CODERANGE(str);
            long beg0, end0;
            VALUE match, match0 = Qnil;
            struct re_registers *regs;
            char *p, *rp;
            long len, rlen;

            match = rb_backref_get();
            regs = RMATCH_REGS(match);
            if (RB_TYPE_P(pat, T_STRING)) {
                beg0 = beg;
                end0 = beg0 + RSTRING_LEN(pat);
                match0 = pat;
            }
            else {
                beg0 = BEG(0);
                end0 = END(0);
                if (iter) match0 = rb_reg_nth_match(0, match);
            }

            if (iter || !NIL_P(hash)) {
                p = RSTRING_PTR(str); len = RSTRING_LEN(str);

                if (iter) {
                    repl = rb_obj_as_string(rb_yield(match0));
                }
                else {
                    repl = rb_hash_aref(hash, rb_str_subseq(str, beg0, end0 - beg0));
                    repl = rb_obj_as_string(repl);
                }
                str_mod_check(str, p, len);
                rb_check_frozen(str);
            }
            else {
                repl = rb_reg_regsub(repl, str, regs, RB_TYPE_P(pat, T_STRING) ? Qnil : pat);
            }

            enc = rb_enc_compatible(str, repl);
            if (!enc) {
                rb_encoding *str_enc = STR_ENC_GET(str);
                p = RSTRING_PTR(str); len = RSTRING_LEN(str);
                if (coderange_scan(p, beg0, str_enc) != ENC_CODERANGE_7BIT ||
                    coderange_scan(p+end0, len-end0, str_enc) != ENC_CODERANGE_7BIT) {
                    rb_raise(rb_eEncCompatError, "incompatible character encodings: %s and %s",
                             rb_enc_inspect_name(str_enc),
                             rb_enc_inspect_name(STR_ENC_GET(repl)));
                }
                enc = STR_ENC_GET(repl);
            }
            rb_str_modify(str);
            rb_enc_associate(str, enc);
            if (ENC_CODERANGE_UNKNOWN < cr && cr < ENC_CODERANGE_BROKEN) {
                int cr2 = ENC_CODERANGE(repl);
                if (cr2 == ENC_CODERANGE_BROKEN ||
                    (cr == ENC_CODERANGE_VALID && cr2 == ENC_CODERANGE_7BIT))
                    cr = ENC_CODERANGE_UNKNOWN;
                else
                    cr = cr2;
            }
            plen = end0 - beg0;
            rlen = RSTRING_LEN(repl);
            len = RSTRING_LEN(str);
            if (rlen > plen) {
                RESIZE_CAPA(str, len + rlen - plen);
            }
            p = RSTRING_PTR(str);
            if (rlen != plen) {
                memmove(p + beg0 + rlen, p + beg0 + plen, len - beg0 - plen);
            }
            rp = RSTRING_PTR(repl);
            memmove(p + beg0, rp, rlen);
            len += rlen - plen;
            STR_SET_LEN(str, len);
            TERM_FILL(&RSTRING_PTR(str)[len], TERM_LEN(str));
            ENC_CODERANGE_SET(str, cr);

            RB_GC_GUARD(match);

            return str;
        }
        return Qnil;
    }

Replaces the first occurrence (not all occurrences) of the given `pattern` on `self`; returns `self` if a replacement occurred, `nil` otherwise.

See Substitution Methods.

Related: `String#sub`, `String#gsub`, `String#gsub!`.

succ → new_str
Source

    VALUE
    rb_str_succ(VALUE orig)
    {
        VALUE str;
        str = rb_str_new(RSTRING_PTR(orig), RSTRING_LEN(orig));
        rb_enc_cr_str_copy_for_substr(str, orig);
        return str_succ(str);
    }

Returns the successor to `self`. The successor is calculated by incrementing characters.

The first character to be incremented is the rightmost alphanumeric: or, if no alphanumerics, the rightmost character:

    'THX1138'.succ # => "THX1139"
    '<<koala>>'.succ # => "<<koalb>>"
    '***'.succ # => '**+'

The successor to a digit is another digit, “carrying” to the next-left character for a “rollover” from 9 to 0, and prepending another digit if necessary:

    '00'.succ # => "01"
    '09'.succ # => "10"
    '99'.succ # => "100"

The successor to a letter is another letter of the same case, carrying to the next-left character for a rollover, and prepending another same-case letter if necessary:

    'aa'.succ # => "ab"
    'az'.succ # => "ba"
    'zz'.succ # => "aaa"
    'AA'.succ # => "AB"
    'AZ'.succ # => "BA"
    'ZZ'.succ # => "AAA"

The successor to a non-alphanumeric character is the next character in the underlying character set’s collating sequence, carrying to the next-left character for a rollover, and prepending another character if necessary:

    s = 0.chr * 3
    s # => "\x00\x00\x00"
    s.succ # => "\x00\x00\x01"
    s = 255.chr * 3
    s # => "\xFF\xFF\xFF"
    s.succ # => "\x01\x00\x00\x00"

Carrying can occur between and among mixtures of alphanumeric characters:

    s = 'zz99zz99'
    s.succ # => "aaa00aa00"
    s = '99zz99zz'
    s.succ # => "100aa00aa"

The successor to an empty `String` is a new empty `String`:

    ''.succ # => ""

Also aliased as: next
succ! → self
Source

    static VALUE
    rb_str_succ_bang(VALUE str)
    {
        rb_str_modify(str);
        str_succ(str);
        return str;
    }

Equivalent to `String#succ`, but modifies `self` in place; returns `self`.

Also aliased as: next!
sum(n = 16) → integer
Source

    static VALUE
    rb_str_sum(int argc, VALUE *argv, VALUE str)
    {
        int bits = 16;
        char *ptr, *p, *pend;
        long len;
        VALUE sum = INT2FIX(0);
        unsigned long sum0 = 0;

        if (rb_check_arity(argc, 0, 1) && (bits = NUM2INT(argv[0])) < 0) {
            bits = 0;
        }
        ptr = p = RSTRING_PTR(str);
        len = RSTRING_LEN(str);
        pend = p + len;

        while (p < pend) {
            if (FIXNUM_MAX - UCHAR_MAX < sum0) {
                sum = rb_funcall(sum, '+', 1, LONG2FIX(sum0));
                str_mod_check(str, ptr, len);
                sum0 = 0;
            }
            sum0 += (unsigned char)*p;
            p++;
        }

        if (bits == 0) {
            if (sum0) {
                sum = rb_funcall(sum, '+', 1, LONG2FIX(sum0));
            }
        }
        else {
            if (sum == INT2FIX(0)) {
                if (bits < (int)sizeof(long)*CHAR_BIT) {
                    sum0 &= (((unsigned long)1)<<bits)-1;
                }
                sum = LONG2FIX(sum0);
            }
            else {
                VALUE mod;

                if (sum0) {
                    sum = rb_funcall(sum, '+', 1, LONG2FIX(sum0));
                }

                mod = rb_funcall(INT2FIX(1), idLTLT, 1, INT2FIX(bits));
                mod = rb_funcall(mod, '-', 1, INT2FIX(1));
                sum = rb_funcall(sum, '&', 1, mod);
            }
        }
        return sum;
    }

Returns a basic `n`-bit checksum of the characters in `self`; the checksum is the sum of the binary value of each byte in `self`, modulo `2**n - 1`:

    'hello'.sum     # => 532
    'hello'.sum(4)  # => 4
    'hello'.sum(64) # => 532
    'тест'.sum      # => 1405
    'こんにちは'.sum  # => 2582

This is not a particularly strong checksum.

swapcase(*options) → string
Source

    static VALUE
    rb_str_swapcase(int argc, VALUE *argv, VALUE str)
    {
        rb_encoding *enc;
        OnigCaseFoldType flags = ONIGENC_CASE_UPCASE | ONIGENC_CASE_DOWNCASE;
        VALUE ret;

        flags = check_case_options(argc, argv, flags);
        enc = str_true_enc(str);
        if (RSTRING_LEN(str) == 0 || !RSTRING_PTR(str)) return str_duplicate(rb_cString, str);
        if (flags&ONIGENC_CASE_ASCII_ONLY) {
            ret = rb_str_new(0, RSTRING_LEN(str));
            rb_str_ascii_casemap(str, ret, &flags, enc);
        }
        else {
            ret = rb_str_casemap(str, &flags, enc);
        }
        return ret;
    }

Returns a string containing the characters in `self`, with cases reversed; each uppercase character is downcased; each lowercase character is upcased:

    s = 'Hello World!' # => "Hello World!"
    s.swapcase         # => "hELLO wORLD!"

The casing may be affected by the given `options`; see Case Mapping.

Related: `String#swapcase!`.

swapcase!(*options) → self or nil
Source

    static VALUE
    rb_str_swapcase_bang(int argc, VALUE *argv, VALUE str)
    {
        rb_encoding *enc;
        OnigCaseFoldType flags = ONIGENC_CASE_UPCASE | ONIGENC_CASE_DOWNCASE;

        flags = check_case_options(argc, argv, flags);
        str_modify_keep_cr(str);
        enc = str_true_enc(str);
        if (flags&ONIGENC_CASE_ASCII_ONLY)
            rb_str_ascii_casemap(str, str, &flags, enc);
        else
            str_shared_replace(str, rb_str_casemap(str, &flags, enc));

        if (ONIGENC_CASE_MODIFIED&flags) return str;
        return Qnil;
    }

Upcases each lowercase character in `self`; downcases uppercase character; returns `self` if any changes were made, `nil` otherwise:

    s = 'Hello World!' # => "Hello World!"
    s.swapcase!        # => "hELLO wORLD!"
    s                  # => "hELLO wORLD!"
    ''.swapcase!       # => nil

The casing may be affected by the given `options`; see Case Mapping.

Related: `String#swapcase`.

to_c → complex
Source

    static VALUE
    string_to_c(VALUE self)
    {
        VALUE num;

        rb_must_asciicompat(self);

        (void)parse_comp(rb_str_fill_terminator(self, 1), FALSE, &num);

        return num;
    }

Returns `self` interpreted as a `Complex` object; leading whitespace and trailing garbage are ignored:

    '9'.to_c                 # => (9+0i)
    '2.5'.to_c               # => (2.5+0i)
    '2.5/1'.to_c             # => ((5/2)+0i)
    '-3/2'.to_c              # => ((-3/2)+0i)
    '-i'.to_c                # => (0-1i)
    '45i'.to_c               # => (0+45i)
    '3-4i'.to_c              # => (3-4i)
    '-4e2-4e-2i'.to_c        # => (-400.0-0.04i)
    '-0.0-0.0i'.to_c         # => (-0.0-0.0i)
    '1/2+3/4i'.to_c          # => ((1/2)+(3/4)*i)
    '1.0@0'.to_c             # => (1+0.0i)
    "1.0@#{Math::PI/2}".to_c # => (0.0+1i)
    "1.0@#{Math::PI}".to_c   # => (-1+0.0i)

Returns Complex zero if the string cannot be converted:

    'ruby'.to_c        # => (0+0i)

See `Kernel#Complex`.

to_f → float
Source

    static VALUE
    rb_str_to_f(VALUE str)
    {
        return DBL2NUM(rb_str_to_dbl(str, FALSE));
    }

Returns the result of interpreting leading characters in `self` as a Float:

    '3.14159'.to_f  # => 3.14159
    '1.234e-2'.to_f # => 0.01234

Characters past a leading valid number (in the given `base`) are ignored:

    '3.14 (pi to two places)'.to_f # => 3.14

Returns zero if there is no leading valid number:

    'abcdef'.to_f # => 0.0

to_i(base = 10) → integer
Source

    static VALUE
    rb_str_to_i(int argc, VALUE *argv, VALUE str)
    {
        int base = 10;

        if (rb_check_arity(argc, 0, 1) && (base = NUM2INT(argv[0])) < 0) {
            rb_raise(rb_eArgError, "invalid radix %d", base);
        }
        return rb_str_to_inum(str, base, FALSE);
    }

Returns the result of interpreting leading characters in `self` as an integer in the given `base` (which must be in (0, 2..36)):

    '123456'.to_i     # => 123456
    '123def'.to_i(16) # => 1195503

With `base` zero, string `object` may contain leading characters to specify the actual base:

    '123def'.to_i(0)   # => 123
    '0123def'.to_i(0)  # => 83
    '0b123def'.to_i(0) # => 1
    '0o123def'.to_i(0) # => 83
    '0d123def'.to_i(0) # => 123
    '0x123def'.to_i(0) # => 1195503

Characters past a leading valid number (in the given `base`) are ignored:

    '12.345'.to_i   # => 12
    '12345'.to_i(2) # => 1

Returns zero if there is no leading valid number:

    'abcdef'.to_i # => 0
    '2'.to_i(2)   # => 0

to_r → rational
Source

    static VALUE
    string_to_r(VALUE self)
    {
        VALUE num;

        rb_must_asciicompat(self);

        num = parse_rat(RSTRING_PTR(self), RSTRING_END(self), 0, TRUE);

        if (RB_FLOAT_TYPE_P(num) && !FLOAT_ZERO_P(num))
            rb_raise(rb_eFloatDomainError, "Infinity");
        return num;
    }

Returns the result of interpreting leading characters in `str` as a rational. Leading whitespace and extraneous characters past the end of a valid number are ignored. Digit sequences can be separated by an underscore. If there is not a valid number at the start of `str`, zero is returned. This method never raises an exception.

    '  2  '.to_r       #=> (2/1)
    '300/2'.to_r       #=> (150/1)
    '-9.2'.to_r        #=> (-46/5)
    '-9.2e2'.to_r      #=> (-920/1)
    '1_234_567'.to_r   #=> (1234567/1)
    '21 June 09'.to_r  #=> (21/1)
    '21/06/09'.to_r    #=> (7/2)
    'BWV 1079'.to_r    #=> (0/1)

NOTE: “0.3”.to_r isn’t the same as 0.3.to_r. The former is equivalent to “3/10”.to_r, but the latter isn’t so.

    "0.3".to_r == 3/10r  #=> true
    0.3.to_r   == 3/10r  #=> false

See also `Kernel#Rational`.

to_s → self or string
Source

    static VALUE
    rb_str_to_s(VALUE str)
    {
        if (rb_obj_class(str) != rb_cString) {
            return str_duplicate(rb_cString, str);
        }
        return str;
    }

Returns `self` if `self` is a `String`, or `self` converted to a `String` if `self` is a subclass of `String`.

Also aliased as: to_str
to_str
Alias for: to_s
to_sym → symbol

Returns the `Symbol` corresponding to str, creating the symbol if it did not previously exist. See `Symbol#id2name`.

    "Koala".intern         #=> :Koala
    s = 'cat'.to_sym       #=> :cat
    s == :cat              #=> true
    s = '@cat'.to_sym      #=> :@cat
    s == :@cat             #=> true

This can also be used to create symbols that cannot be represented using the `:xxx` notation.

    'cat and dog'.to_sym   #=> :"cat and dog"

Alias for: intern
tr(selector, replacements) → new_string
Source

    static VALUE
    rb_str_tr(VALUE str, VALUE src, VALUE repl)
    {
        str = str_duplicate(rb_cString, str);
        tr_trans(str, src, repl, 0);
        return str;
    }

Returns a copy of `self` with each character specified by string `selector` translated to the corresponding character in string `replacements`. The correspondence is positional:

- Each occurrence of the first character specified by `selector` is translated to the first character in `replacements`.

- Each occurrence of the second character specified by `selector` is translated to the second character in `replacements`.

- And so on.

Example:

    'hello'.tr('el', 'ip') #=> "hippo"

If `replacements` is shorter than `selector`, it is implicitly padded with its own last character:

    'hello'.tr('aeiou', '-')   # => "h-ll-"
    'hello'.tr('aeiou', 'AA-') # => "hAll-"

Arguments `selector` and `replacements` must be valid character selectors (see Character Selectors), and may use any of its valid forms, including negation, ranges, and escaping:

    # Negation.
    'hello'.tr('^aeiou', '-') # => "-e--o"
    # Ranges.
    'ibm'.tr('b-z', 'a-z') # => "hal"
    # Escapes.
    'hel^lo'.tr('\^aeiou', '-')     # => "h-l-l-"    # Escaped leading caret.
    'i-b-m'.tr('b\-z', 'a-z')       # => "ibabm"     # Escaped embedded hyphen.
    'foo\\bar'.tr('ab\\', 'XYZ')    # => "fooZYXr"   # Escaped backslash.

tr!(selector, replacements) → self or nil
Source

    static VALUE
    rb_str_tr_bang(VALUE str, VALUE src, VALUE repl)
    {
        return tr_trans(str, src, repl, 0);
    }

Like `String#tr`, but modifies `self` in place. Returns `self` if any changes were made, `nil` otherwise.

tr_s(selector, replacements) → string
Source

    static VALUE
    rb_str_tr_s(VALUE str, VALUE src, VALUE repl)
    {
        str = str_duplicate(rb_cString, str);
        tr_trans(str, src, repl, 1);
        return str;
    }

Like `String#tr`, but also squeezes the modified portions of the translated string; returns a new string (translated and squeezed).

    'hello'.tr_s('l', 'r')   #=> "hero"
    'hello'.tr_s('el', '-')  #=> "h-o"
    'hello'.tr_s('el', 'hx') #=> "hhxo"

Related: `String#squeeze`.

tr_s!(selector, replacements) → self or nil
Source

    static VALUE
    rb_str_tr_s_bang(VALUE str, VALUE src, VALUE repl)
    {
        return tr_trans(str, src, repl, 1);
    }

Like `String#tr_s`, but modifies `self` in place. Returns `self` if any changes were made, `nil` otherwise.

Related: `String#squeeze!`.

undump → string
Source

    static VALUE
    str_undump(VALUE str)
    {
        const char *s = RSTRING_PTR(str);
        const char *s_end = RSTRING_END(str);
        rb_encoding *enc = rb_enc_get(str);
        VALUE undumped = rb_enc_str_new(s, 0L, enc);
        bool utf8 = false;
        bool binary = false;
        int w;

        rb_must_asciicompat(str);
        if (rb_str_is_ascii_only_p(str) == Qfalse) {
            rb_raise(rb_eRuntimeError, "non-ASCII character detected");
        }
        if (!str_null_check(str, &w)) {
            rb_raise(rb_eRuntimeError, "string contains null byte");
        }
        if (RSTRING_LEN(str) < 2) goto invalid_format;
        if (*s != '"') goto invalid_format;

        /* strip '"' at the start */
        s++;

        for (;;) {
            if (s >= s_end) {
                rb_raise(rb_eRuntimeError, "unterminated dumped string");
            }

            if (*s == '"') {
                /* epilogue */
                s++;
                if (s == s_end) {
                    /* ascii compatible dumped string */
                    break;
                }
                else {
                    static const char force_encoding_suffix[] = ".force_encoding(\""; /* "\")" */
                    static const char dup_suffix[] = ".dup";
                    const char *encname;
                    int encidx;
                    ptrdiff_t size;

                    /* check separately for strings dumped by older versions */
                    size = sizeof(dup_suffix) - 1;
                    if (s_end - s > size && memcmp(s, dup_suffix, size) == 0) s += size;

                    size = sizeof(force_encoding_suffix) - 1;
                    if (s_end - s <= size) goto invalid_format;
                    if (memcmp(s, force_encoding_suffix, size) != 0) goto invalid_format;
                    s += size;

                    if (utf8) {
                        rb_raise(rb_eRuntimeError, "dumped string contained Unicode escape but used force_encoding");
                    }

                    encname = s;
                    s = memchr(s, '"', s_end-s);
                    size = s - encname;
                    if (!s) goto invalid_format;
                    if (s_end - s != 2) goto invalid_format;
                    if (s[0] != '"' || s[1] != ')') goto invalid_format;

                    encidx = rb_enc_find_index2(encname, (long)size);
                    if (encidx < 0) {
                        rb_raise(rb_eRuntimeError, "dumped string has unknown encoding name");
                    }
                    rb_enc_associate_index(undumped, encidx);
                }
                break;
            }

            if (*s == '\\') {
                s++;
                if (s >= s_end) {
                    rb_raise(rb_eRuntimeError, "invalid escape");
                }
                undump_after_backslash(undumped, &s, s_end, &enc, &utf8, &binary);
            }
            else {
                rb_str_cat(undumped, s++, 1);
            }
        }

        RB_GC_GUARD(str);

        return undumped;
    invalid_format:
        rb_raise(rb_eRuntimeError, "invalid dumped string; not wrapped with '\"' nor '\"...\".force_encoding(\"...\")' form");
    }

Returns an unescaped version of `self`:

    s_orig = "\f\x00\xff\\\""    # => "\f\u0000\xFF\\\""
    s_dumped = s_orig.dump       # => "\"\\f\\x00\\xFF\\\\\\\"\""
    s_undumped = s_dumped.undump # => "\f\u0000\xFF\\\""
    s_undumped == s_orig         # => true

Related: `String#dump` (inverse of `String#undump`).

unicode_normalize(form = :nfc) → string
Source

    static VALUE
    rb_str_unicode_normalize(int argc, VALUE *argv, VALUE str)
    {
        return unicode_normalize_common(argc, argv, str, id_normalize);
    }

Returns a copy of `self` with Unicode normalization applied.

Argument `form` must be one of the following symbols (see Unicode normalization forms):

- `:nfc`: Canonical decomposition, followed by canonical composition.

- `:nfd`: Canonical decomposition.

- `:nfkc`: Compatibility decomposition, followed by canonical composition.

- `:nfkd`: Compatibility decomposition.

The encoding of `self` must be one of:

- Encoding::UTF_8

- Encoding::UTF_16BE

- Encoding::UTF_16LE

- Encoding::UTF_32BE

- Encoding::UTF_32LE

- Encoding::GB18030

- Encoding::UCS_2BE

- Encoding::UCS_4BE

Examples:

    "a\u0300".unicode_normalize      # => "a"
    "\u00E0".unicode_normalize(:nfd) # => "a "

Related: `String#unicode_normalize!`, `String#unicode_normalized?`.

unicode_normalize!(form = :nfc) → self
Source

    static VALUE
    rb_str_unicode_normalize_bang(int argc, VALUE *argv, VALUE str)
    {
        return rb_str_replace(str, unicode_normalize_common(argc, argv, str, id_normalize));
    }

Like `String#unicode_normalize`, except that the normalization is performed on `self`.

Related `String#unicode_normalized?`.

unicode_normalized?(form = :nfc) → true or false
Source

    static VALUE
    rb_str_unicode_normalized_p(int argc, VALUE *argv, VALUE str)
    {
        return unicode_normalize_common(argc, argv, str, id_normalized_p);
    }

Returns `true` if `self` is in the given `form` of Unicode normalization, `false` otherwise. The `form` must be one of `:nfc`, `:nfd`, `:nfkc`, or `:nfkd`.

Examples:

    "a\u0300".unicode_normalized?       # => false
    "a\u0300".unicode_normalized?(:nfd) # => true
    "\u00E0".unicode_normalized?        # => true
    "\u00E0".unicode_normalized?(:nfd)  # => false

Raises an exception if `self` is not in a Unicode encoding:

    s = "\xE0".force_encoding('ISO-8859-1')
    s.unicode_normalized? # Raises Encoding::CompatibilityError.

Related: `String#unicode_normalize`, `String#unicode_normalize!`.

unpack(template, offset: 0, &block) → array
Source

    # File pack.rb, line 23
    def unpack(fmt, offset: 0)
      Primitive.attr! :use_block
      Primitive.pack_unpack(fmt, offset)
    end

Extracts data from `self`.

If `block` is not given, forming objects that become the elements of a new array, and returns that array. Otherwise, yields each object.

See Packed Data.

unpack1(template, offset: 0) → object
Source

    # File pack.rb, line 33
    def unpack1(fmt, offset: 0)
      Primitive.pack_unpack1(fmt, offset)
    end

Like `String#unpack`, but unpacks and returns only the first extracted object. See Packed Data.

upcase(*options) → string
Source

    static VALUE
    rb_str_upcase(int argc, VALUE *argv, VALUE str)
    {
        rb_encoding *enc;
        OnigCaseFoldType flags = ONIGENC_CASE_UPCASE;
        VALUE ret;

        flags = check_case_options(argc, argv, flags);
        enc = str_true_enc(str);
        if (case_option_single_p(flags, enc, str)) {
            ret = rb_str_new(RSTRING_PTR(str), RSTRING_LEN(str));
            str_enc_copy_direct(ret, str);
            upcase_single(ret);
        }
        else if (flags&ONIGENC_CASE_ASCII_ONLY) {
            ret = rb_str_new(0, RSTRING_LEN(str));
            rb_str_ascii_casemap(str, ret, &flags, enc);
        }
        else {
            ret = rb_str_casemap(str, &flags, enc);
        }

        return ret;
    }

Returns a string containing the upcased characters in `self`:

    s = 'Hello World!' # => "Hello World!"
    s.upcase           # => "HELLO WORLD!"

The casing may be affected by the given `options`; see Case Mapping.

Related: `String#upcase!`, `String#downcase`, `String#downcase!`.

upcase!(*options) → self or nil
Source

    static VALUE
    rb_str_upcase_bang(int argc, VALUE *argv, VALUE str)
    {
        rb_encoding *enc;
        OnigCaseFoldType flags = ONIGENC_CASE_UPCASE;

        flags = check_case_options(argc, argv, flags);
        str_modify_keep_cr(str);
        enc = str_true_enc(str);
        if (case_option_single_p(flags, enc, str)) {
            if (upcase_single(str))
                flags |= ONIGENC_CASE_MODIFIED;
        }
        else if (flags&ONIGENC_CASE_ASCII_ONLY)
            rb_str_ascii_casemap(str, str, &flags, enc);
        else
            str_shared_replace(str, rb_str_casemap(str, &flags, enc));

        if (ONIGENC_CASE_MODIFIED&flags) return str;
        return Qnil;
    }

Upcases the characters in `self`; returns `self` if any changes were made, `nil` otherwise:

    s = 'Hello World!' # => "Hello World!"
    s.upcase!          # => "HELLO WORLD!"
    s                  # => "HELLO WORLD!"
    s.upcase!          # => nil

The casing may be affected by the given `options`; see Case Mapping.

Related: `String#upcase`, `String#downcase`, `String#downcase!`.

upto(other_string, exclusive = false) {|string| ... } → self
upto(other_string, exclusive = false) → new_enumerator
Source

    static VALUE
    rb_str_upto(int argc, VALUE *argv, VALUE beg)
    {
        VALUE end, exclusive;

        rb_scan_args(argc, argv, "11", &end, &exclusive);
        RETURN_ENUMERATOR(beg, argc, argv);
        return rb_str_upto_each(beg, end, RTEST(exclusive), str_upto_i, Qnil);
    }

With a block given, calls the block with each `String` value returned by successive calls to `String#succ`; the first value is `self`, the next is `self.succ`, and so on; the sequence terminates when value `other_string` is reached; returns `self`:

    'a8'.upto('b6') {|s| print s, ' ' } # => "a8"

Output:

    a8 a9 b0 b1 b2 b3 b4 b5 b6

If argument `exclusive` is given as a truthy object, the last value is omitted:

    'a8'.upto('b6', true) {|s| print s, ' ' } # => "a8"

Output:

    a8 a9 b0 b1 b2 b3 b4 b5

If `other_string` would not be reached, does not call the block:

    '25'.upto('5') {|s| fail s }
    'aa'.upto('a') {|s| fail s }

With no block given, returns a new Enumerator:

    'a8'.upto('b6') # => #<Enumerator: "a8":upto("b6")>

valid_encoding? → true or false
Source

    static VALUE
    rb_str_valid_encoding_p(VALUE str)
    {
        int cr = rb_enc_str_coderange(str);

        return RBOOL(cr != ENC_CODERANGE_BROKEN);
    }

Returns `true` if `self` is encoded correctly, `false` otherwise:

    "\xc2\xa1".force_encoding("UTF-8").valid_encoding? # => true
    "\xc2".force_encoding("UTF-8").valid_encoding?     # => false
    "\x80".force_encoding("UTF-8").valid_encoding?     # => false