# class IO

An instance of class IO (commonly called a stream) represents an input/output stream in the underlying operating system. Class IO is the basis for input and output in Ruby.

Class `File` is the only class in the Ruby core that is a subclass of IO. Some classes in the Ruby standard library are also subclasses of IO; these include `TCPSocket` and `UDPSocket`.

The global constant `ARGF` (also accessible as `$<`) provides an IO-like stream that allows access to all file paths found in ARGV (or found in STDIN if ARGV is empty). `ARGF` is not itself a subclass of IO.

Class `StringIO` provides an IO-like stream that handles a `String`. `StringIO` is not itself a subclass of IO.

Important objects based on IO include:

- $stdin.

- $stdout.

- $stderr.

- Instances of class `File`.

An instance of IO may be created using:

- `IO.new`: returns a new IO object for the given integer file descriptor.

- `IO.open`: passes a new IO object to the given block.

- `IO.popen`: returns a new IO object that is connected to the $stdin and $stdout of a newly-launched subprocess.

- `Kernel#open`: Returns a new IO object connected to a given source: stream, file, or subprocess.

Like a `File` stream, an IO stream has:

- A read/write mode, which may be read-only, write-only, or read/write; see Read/Write Mode.

- A data mode, which may be text-only or binary; see Data Mode.

- Internal and external encodings; see Encodings.

And like other IO streams, it has:

- A position, which determines where in the stream the next read or write is to occur; see Position.

- A line number, which is a special, line-oriented, “position” (different from the position mentioned above); see Line Number.

## Extension `io/console`¶ ↑

Extension `io/console` provides numerous methods for interacting with the console; requiring it adds numerous methods to class IO.

## Example Files¶ ↑

Many examples here use these variables:

    # English text with newlines.
    text = <<~EOT
      First line
      Second line

      Fourth line
      Fifth line
    EOT

    # Russian text.
    russian = "\u{442 435 441 442}" # => "тест"

    # Binary data.
    data = "\u9990\u9991\u9992\u9993\u9994"

    # Text file.
    File.write('t.txt', text)

    # File with Russian text.
    File.write('t.rus', russian)

    # File with binary data.
    f = File.new('t.dat', 'wb:UTF-16')
    f.write(data)
    f.close

## Open Options¶ ↑

A number of IO methods accept optional keyword arguments that determine how a new stream is to be opened:

- `:mode`: Stream mode.

- `:flags`: `Integer` file open flags; If `mode` is also given, the two are bitwise-ORed.

- `:external_encoding`: External encoding for the stream.

- `:internal_encoding`: Internal encoding for the stream. `'-'` is a synonym for the default internal encoding. If the value is `nil` no conversion occurs.

- `:encoding`: Specifies external and internal encodings as `'extern:intern'`.

- `:textmode`: If a truthy value, specifies the mode as text-only, binary otherwise.

- `:binmode`: If a truthy value, specifies the mode as binary, text-only otherwise.

- `:autoclose`: If a truthy value, specifies that the `fd` will close when the stream closes; otherwise it remains open.

- `:path:` If a string value is provided, it is used in `inspect` and is available as `path` method.

Also available are the options offered in `String#encode`, which may control conversion between external and internal encoding.

## Basic IO¶ ↑

You can perform basic stream IO with these methods, which typically operate on multi-byte strings:

- `IO#read`: Reads and returns some or all of the remaining bytes from the stream.

- `IO#write`: Writes zero or more strings to the stream; each given object that is not already a string is converted via `to_s`.

### Position¶ ↑

An IO stream has a nonnegative integer position, which is the byte offset at which the next read or write is to occur. A new stream has position zero (and line number zero); method `rewind` resets the position (and line number) to zero.

These methods discard buffers and the `Encoding::Converter` instances used for that IO.

The relevant methods:

- `IO#tell` (aliased as `pos`): Returns the current position (in bytes) in the stream.

- `IO#pos=`: Sets the position of the stream to a given integer `new_position` (in bytes).

- `IO#seek`: Sets the position of the stream to a given integer `offset` (in bytes), relative to a given position `whence` (indicating the beginning, end, or current position).

- `IO#rewind`: Positions the stream at the beginning (also resetting the line number).

### Open and Closed Streams¶ ↑

A new IO stream may be open for reading, open for writing, or both.

A stream is automatically closed when claimed by the garbage collector.

Attempted reading or writing on a closed stream raises an exception.

The relevant methods:

- `IO#close`: Closes the stream for both reading and writing.

- `IO#close_read`: Closes the stream for reading.

- `IO#close_write`: Closes the stream for writing.

- `IO#closed?`: Returns whether the stream is closed.

### End-of-Stream¶ ↑

You can query whether a stream is positioned at its end:

- `IO#eof?` (also aliased as `eof`): Returns whether the stream is at end-of-stream.

You can reposition to end-of-stream by using method `IO#seek`:

    f = File.new('t.txt')
    f.eof? # => false
    f.seek(0, :END)
    f.eof? # => true
    f.close

Or by reading all stream content (which is slower than using `IO#seek`):

    f.rewind
    f.eof? # => false
    f.read # => "First line\nSecond line\n\nFourth line\nFifth line\n"
    f.eof? # => true

## Line IO¶ ↑

Class IO supports line-oriented input and output

### Line Input¶ ↑

Class IO supports line-oriented input for files and IO streams

#### File Line Input¶ ↑

You can read lines from a file using these methods:

- `IO.foreach`: Reads each line and passes it to the given block.

- `IO.readlines`: Reads and returns all lines in an array.

For each of these methods:

- You can specify open options.

- Line parsing depends on the effective line separator; see Line Separator.

- The length of each returned line depends on the effective line limit; see Line Limit.

#### Stream Line Input¶ ↑

You can read lines from an IO stream using these methods:

- `IO#each_line`: Reads each remaining line, passing it to the given block.

- `IO#gets`: Returns the next line.

- `IO#readline`: Like `gets`, but raises an exception at end-of-stream.

- `IO#readlines`: Returns all remaining lines in an array.

For each of these methods:

- Reading may begin mid-line, depending on the stream’s position; see Position.

- Line parsing depends on the effective line separator; see Line Separator.

- The length of each returned line depends on the effective line limit; see Line Limit.

##### Line Separator¶ ↑

Each of the line input methods uses a line separator: the string that determines what is considered a line; it is sometimes called the input record separator.

The default line separator is taken from global variable `$/`, whose initial value is `"\n"`.

Generally, the line to be read next is all data from the current position to the next line separator (but see Special Line Separator Values):

    f = File.new('t.txt')
    # Method gets with no sep argument returns the next line, according to $/.
    f.gets # => "First line\n"
    f.gets # => "Second line\n"
    f.gets # => "\n"
    f.gets # => "Fourth line\n"
    f.gets # => "Fifth line\n"
    f.close

You can use a different line separator by passing argument `sep`:

    f = File.new('t.txt')
    f.gets('l')   # => "First l"
    f.gets('li')  # => "ine\nSecond li"
    f.gets('lin') # => "ne\n\nFourth lin"
    f.gets        # => "e\n"
    f.close

Or by setting global variable `$/`:

    f = File.new('t.txt')
    $/ = 'l'
    f.gets # => "First l"
    f.gets # => "ine\nSecond l"
    f.gets # => "ine\n\nFourth l"
    f.close

##### Special Line Separator Values¶ ↑

Each of the line input methods accepts two special values for parameter `sep`:

- `nil`: The entire stream is to be read (“slurped”) into a single string:

      f = File.new('t.txt')
      f.gets(nil) # => "First line\nSecond line\n\nFourth line\nFifth line\n"
      f.close

- `''` (the empty string): The next “paragraph” is to be read (paragraphs being separated by two consecutive line separators):

      f = File.new('t.txt')
      f.gets('') # => "First line\nSecond line\n\n"
      f.gets('') # => "Fourth line\nFifth line\n"
      f.close

##### Line Limit¶ ↑

Each of the line input methods uses an integer line limit, which restricts the number of bytes that may be returned. (A multi-byte character will not be split, and so a returned line may be slightly longer than the limit).

The default limit value is `-1`; any negative limit value means that there is no limit.

If there is no limit, the line is determined only by `sep`.

    # Text with 1-byte characters.
    File.open('t.txt') {|f| f.gets(1) }  # => "F"
    File.open('t.txt') {|f| f.gets(2) }  # => "Fi"
    File.open('t.txt') {|f| f.gets(3) }  # => "Fir"
    File.open('t.txt') {|f| f.gets(4) }  # => "Firs"
    # No more than one line.
    File.open('t.txt') {|f| f.gets(10) } # => "First line"
    File.open('t.txt') {|f| f.gets(11) } # => "First line\n"
    File.open('t.txt') {|f| f.gets(12) } # => "First line\n"

    # Text with 2-byte characters, which will not be split.
    File.open('t.rus') {|f| f.gets(1).size } # => 1
    File.open('t.rus') {|f| f.gets(2).size } # => 1
    File.open('t.rus') {|f| f.gets(3).size } # => 2
    File.open('t.rus') {|f| f.gets(4).size } # => 2

##### Line Separator and Line Limit¶ ↑

With arguments `sep` and `limit` given, combines the two behaviors:

- Returns the next line as determined by line separator `sep`.

- But returns no more bytes than are allowed by the limit `limit`.

Example:

    File.open('t.txt') {|f| f.gets('li', 20) } # => "First li"
    File.open('t.txt') {|f| f.gets('li', 2) }  # => "Fi"

##### Line Number¶ ↑

A readable IO stream has a non-negative integer line number:

- `IO#lineno`: Returns the line number.

- `IO#lineno=`: Resets and returns the line number.

Unless modified by a call to method `IO#lineno=`, the line number is the number of lines read by certain line-oriented methods, according to the effective line separator:

- `IO.foreach`: Increments the line number on each call to the block.

- `IO#each_line`: Increments the line number on each call to the block.

- `IO#gets`: Increments the line number.

- `IO#readline`: Increments the line number.

- `IO#readlines`: Increments the line number for each line read.

A new stream is initially has line number zero (and position zero); method `rewind` resets the line number (and position) to zero:

    f = File.new('t.txt')
    f.lineno # => 0
    f.gets   # => "First line\n"
    f.lineno # => 1
    f.rewind
    f.lineno # => 0
    f.close

Reading lines from a stream usually changes its line number:

    f = File.new('t.txt', 'r')
    f.lineno   # => 0
    f.readline # => "This is line one.\n"
    f.lineno   # => 1
    f.readline # => "This is the second line.\n"
    f.lineno   # => 2
    f.readline # => "Here's the third line.\n"
    f.lineno   # => 3
    f.eof?     # => true
    f.close

Iterating over lines in a stream usually changes its line number:

    File.open('t.txt') do |f|
      f.each_line do |line|
        p "position=#{f.pos} eof?=#{f.eof?} lineno=#{f.lineno}"
      end
    end

Output:

    "position=11 eof?=false lineno=1"
    "position=23 eof?=false lineno=2"
    "position=24 eof?=false lineno=3"
    "position=36 eof?=false lineno=4"
    "position=47 eof?=true lineno=5"

Unlike the stream’s position, the line number does not affect where the next read or write will occur:

    f = File.new('t.txt')
    f.lineno = 1000
    f.lineno # => 1000
    f.gets   # => "First line\n"
    f.lineno # => 1001
    f.close

Associated with the line number is the global variable `$.`:

- When a stream is opened, `$.` is not set; its value is left over from previous activity in the process:

      $. = 41
      f = File.new('t.txt')
      $. = 41
      # => 41
      f.close

- When a stream is read, `$.` is set to the line number for that stream:

      f0 = File.new('t.txt')
      f1 = File.new('t.dat')
      f0.readlines # => ["First line\n", "Second line\n", "\n", "Fourth line\n", "Fifth line\n"]
      $.           # => 5
      f1.readlines # => ["\xFE\xFF\x99\x90\x99\x91\x99\x92\x99\x93\x99\x94"]
      $.           # => 1
      f0.close
      f1.close

- Methods `IO#rewind` and `IO#seek` do not affect `$.`:

      f = File.new('t.txt')
      f.readlines # => ["First line\n", "Second line\n", "\n", "Fourth line\n", "Fifth line\n"]
      $.          # => 5
      f.rewind
      f.seek(0, :SET)
      $.          # => 5
      f.close

### Line Output¶ ↑

You can write to an IO stream line-by-line using this method:

- `IO#puts`: Writes objects to the stream.

## Character IO¶ ↑

You can process an IO stream character-by-character using these methods:

- `IO#getc`: Reads and returns the next character from the stream.

- `IO#readchar`: Like `getc`, but raises an exception at end-of-stream.

- `IO#ungetc`: Pushes back (“unshifts”) a character or integer onto the stream.

- `IO#putc`: Writes a character to the stream.

- `IO#each_char`: Reads each remaining character in the stream, passing the character to the given block.

## Byte IO¶ ↑

You can process an IO stream byte-by-byte using these methods:

- `IO#getbyte`: Returns the next 8-bit byte as an integer in range 0..255.

- `IO#readbyte`: Like `getbyte`, but raises an exception if at end-of-stream.

- `IO#ungetbyte`: Pushes back (“unshifts”) a byte back onto the stream.

- `IO#each_byte`: Reads each remaining byte in the stream, passing the byte to the given block.

## Codepoint IO¶ ↑

You can process an IO stream codepoint-by-codepoint:

- `IO#each_codepoint`: Reads each remaining codepoint, passing it to the given block.

## What’s Here¶ ↑

First, what’s elsewhere. Class IO:

- Inherits from class Object.

- Includes module Enumerable, which provides dozens of additional methods.

Here, class IO provides methods that are useful for:

- Creating

- Reading

- Writing

- Positioning

- Iterating

- Settings

- Querying

- Buffering

- Low-Level Access

- Other

### Creating¶ ↑

- `::new` (aliased as `::for_fd`): Creates and returns a new IO object for the given integer file descriptor.

- `::open`: Creates a new IO object.

- `::pipe`: Creates a connected pair of reader and writer IO objects.

- `::popen`: Creates an IO object to interact with a subprocess.

- `::select`: Selects which given IO instances are ready for reading, writing, or have pending exceptions.

### Reading¶ ↑

- `::binread`: Returns a binary string with all or a subset of bytes from the given file.

- `::read`: Returns a string with all or a subset of bytes from the given file.

- `::readlines`: Returns an array of strings, which are the lines from the given file.

- `getbyte`: Returns the next 8-bit byte read from `self` as an integer.

- `getc`: Returns the next character read from `self` as a string.

- `gets`: Returns the line read from `self`.

- `pread`: Returns all or the next n bytes read from `self`, not updating the receiver’s offset.

- `read`: Returns all remaining or the next n bytes read from `self` for a given n.

- `read_nonblock`: the next n bytes read from `self` for a given n, in non-block mode.

- `readbyte`: Returns the next byte read from `self`; same as `getbyte`, but raises an exception on end-of-stream.

- `readchar`: Returns the next character read from `self`; same as `getc`, but raises an exception on end-of-stream.

- `readline`: Returns the next line read from `self`; same as getline, but raises an exception of end-of-stream.

- `readlines`: Returns an array of all lines read read from `self`.

- `readpartial`: Returns up to the given number of bytes from `self`.

### Writing¶ ↑

- `::binwrite`: Writes the given string to the file at the given filepath, in binary mode.

- `::write`: Writes the given string to `self`.

- `<<`: Appends the given string to `self`.

- `print`: Prints last read line or given objects to `self`.

- `printf`: Writes to `self` based on the given format string and objects.

- `putc`: Writes a character to `self`.

- `puts`: Writes lines to `self`, making sure line ends with a newline.

- `pwrite`: Writes the given string at the given offset, not updating the receiver’s offset.

- `write`: Writes one or more given strings to `self`.

- `write_nonblock`: Writes one or more given strings to `self` in non-blocking mode.

### Positioning¶ ↑

- `lineno`: Returns the current line number in `self`.

- `lineno=`: Sets the line number is `self`.

- `pos` (aliased as `tell`): Returns the current byte offset in `self`.

- `pos=`: Sets the byte offset in `self`.

- `reopen`: Reassociates `self` with a new or existing IO stream.

- `rewind`: Positions `self` to the beginning of input.

- `seek`: Sets the offset for `self` relative to given position.

### Iterating¶ ↑

- `::foreach`: Yields each line of given file to the block.

- `each` (aliased as `each_line`): Calls the given block with each successive line in `self`.

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

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

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

### Settings¶ ↑

- `autoclose=`: Sets whether `self` auto-closes.

- `binmode`: Sets `self` to binary mode.

- `close`: Closes `self`.

- `close_on_exec=`: Sets the close-on-exec flag.

- `close_read`: Closes `self` for reading.

- `close_write`: Closes `self` for writing.

- `set_encoding`: Sets the encoding for `self`.

- `set_encoding_by_bom`: Sets the encoding for `self`, based on its Unicode byte-order-mark.

- `sync=`: Sets the sync-mode to the given value.

### Querying¶ ↑

- `autoclose?`: Returns whether `self` auto-closes.

- `binmode?`: Returns whether `self` is in binary mode.

- `close_on_exec?`: Returns the close-on-exec flag for `self`.

- `closed?`: Returns whether `self` is closed.

- `eof?` (aliased as `eof`): Returns whether `self` is at end-of-stream.

- `external_encoding`: Returns the external encoding object for `self`.

- `fileno` (aliased as `to_i`): Returns the integer file descriptor for `self`

- `internal_encoding`: Returns the internal encoding object for `self`.

- `pid`: Returns the process ID of a child process associated with `self`, if `self` was created by `::popen`.

- `stat`: Returns the `File::Stat` object containing status information for `self`.

- `sync`: Returns whether `self` is in sync-mode.

- `tty?` (aliased as `isatty`): Returns whether `self` is a terminal.

### Buffering¶ ↑

- `fdatasync`: Immediately writes all buffered data in `self` to disk.

- `flush`: Flushes any buffered data within `self` to the underlying operating system.

- `fsync`: Immediately writes all buffered data and attributes in `self` to disk.

- `ungetbyte`: Prepends buffer for `self` with given integer byte or string.

- `ungetc`: Prepends buffer for `self` with given string.

### Low-Level Access¶ ↑

- `::sysopen`: Opens the file given by its path, returning the integer file descriptor.

- `advise`: Announces the intention to access data from `self` in a specific way.

- `fcntl`: Passes a low-level command to the file specified by the given file descriptor.

- `ioctl`: Passes a low-level command to the device specified by the given file descriptor.

- `sysread`: Returns up to the next n bytes read from self using a low-level read.

- `sysseek`: Sets the offset for `self`.

- `syswrite`: Writes the given string to `self` using a low-level write.

### Other¶ ↑

- `::copy_stream`: Copies data from a source to a destination, each of which is a filepath or an IO-like object.

- `::try_convert`: Returns a new IO object resulting from converting the given object.

- `inspect`: Returns the string representation of `self`.

### Constants

EWOULDBLOCKWaitReadable

  same as `IO::EAGAINWaitReadable`

EWOULDBLOCKWaitWritable

  same as `IO::EAGAINWaitWritable`

PRIORITY

  Priority event mask for `IO#wait`.

READABLE

  Readable event mask for `IO#wait`.

SEEK_CUR

  `Set` I/O position from the current position

SEEK_DATA

  `Set` I/O position to the next location containing data

SEEK_END

  `Set` I/O position from the end

SEEK_HOLE

  `Set` I/O position to the next hole

SEEK_SET

  `Set` I/O position from the beginning

WRITABLE

  Writable event mask for `IO#wait`.

### Public Class Methods

binread(path, length = nil, offset = 0) → string or nil
Source

    static VALUE
    rb_io_s_binread(int argc, VALUE *argv, VALUE io)
    {
        VALUE offset;
        struct foreach_arg arg;
        enum {
            fmode = FMODE_READABLE|FMODE_BINMODE,
            oflags = O_RDONLY
    #ifdef O_BINARY
                    |O_BINARY
    #endif
        };
        struct rb_io_encoding convconfig = {NULL, NULL, 0, Qnil};

        rb_scan_args(argc, argv, "12", NULL, NULL, &offset);
        FilePathValue(argv[0]);
        convconfig.enc = rb_ascii8bit_encoding();
        arg.io = rb_io_open_generic(io, argv[0], oflags, fmode, &convconfig, 0);
        if (NIL_P(arg.io)) return Qnil;
        arg.argv = argv+1;
        arg.argc = (argc > 1) ? 1 : 0;
        if (!NIL_P(offset)) {
            struct seek_arg sarg;
            int state = 0;
            sarg.io = arg.io;
            sarg.offset = offset;
            sarg.mode = SEEK_SET;
            rb_protect(seek_before_access, (VALUE)&sarg, &state);
            if (state) {
                rb_io_close(arg.io);
                rb_jump_tag(state);
            }
        }
        return rb_ensure(io_s_read, (VALUE)&arg, rb_io_close, arg.io);
    }

Behaves like `IO.read`, except that the stream is opened in binary mode with ASCII-8BIT encoding.

When called from class IO (but not subclasses of IO), this method has potential security vulnerabilities if called with untrusted input; see Command Injection.

binwrite(path, string, offset = 0) → integer
Source

    static VALUE
    rb_io_s_binwrite(int argc, VALUE *argv, VALUE io)
    {
        return io_s_write(argc, argv, io, 1);
    }

Behaves like `IO.write`, except that the stream is opened in binary mode with ASCII-8BIT encoding.

When called from class IO (but not subclasses of IO), this method has potential security vulnerabilities if called with untrusted input; see Command Injection.

console → #<File:/dev/tty>
console(sym, *args)
Source

    static VALUE
    console_dev(int argc, VALUE *argv, VALUE klass)
    {
        VALUE con = 0;
        VALUE sym = 0;

        rb_check_arity(argc, 0, UNLIMITED_ARGUMENTS);

        if (argc) {
            Check_Type(sym = argv[0], T_SYMBOL);
        }

        // Force the class to be File.
        if (klass == rb_cIO) klass = rb_cFile;

        if (console_dev_get(klass, &con)) {
            if (!RB_TYPE_P(con, T_FILE) || RTEST(rb_io_closed_p(con))) {
                console_dev_remove(klass);
                con = 0;
            }
        }

        if (sym) {
            if (sym == ID2SYM(id_close) && argc == 1) {
                if (con) {
                    rb_io_close(con);
                    console_dev_remove(klass);
                    con = 0;
                }
                return Qnil;
            }
        }

        if (!con) {
    #if defined HAVE_TERMIOS_H || defined HAVE_TERMIO_H || defined HAVE_SGTTY_H
    # define CONSOLE_DEVICE "/dev/tty"
    #elif defined _WIN32
    # define CONSOLE_DEVICE "con$"
    # define CONSOLE_DEVICE_FOR_READING "conin$"
    # define CONSOLE_DEVICE_FOR_WRITING "conout$"
    #endif
    #ifndef CONSOLE_DEVICE_FOR_READING
    # define CONSOLE_DEVICE_FOR_READING CONSOLE_DEVICE
    #endif
    #ifdef CONSOLE_DEVICE_FOR_WRITING
            VALUE out;
    #endif
            int fd;
            VALUE path = rb_obj_freeze(rb_str_new2(CONSOLE_DEVICE));

    #ifdef CONSOLE_DEVICE_FOR_WRITING
            fd = rb_cloexec_open(CONSOLE_DEVICE_FOR_WRITING, O_RDWR, 0);
            if (fd < 0) return Qnil;
            out = rb_io_open_descriptor(klass, fd, FMODE_WRITABLE | FMODE_SYNC, path, Qnil, NULL);
    #endif
            fd = rb_cloexec_open(CONSOLE_DEVICE_FOR_READING, O_RDWR, 0);
            if (fd < 0) {
    #ifdef CONSOLE_DEVICE_FOR_WRITING
                rb_io_close(out);
    #endif
                return Qnil;
            }

            con = rb_io_open_descriptor(klass, fd, FMODE_READWRITE | FMODE_SYNC, path, Qnil, NULL);
    #ifdef CONSOLE_DEVICE_FOR_WRITING
            rb_io_set_write_io(con, out);
    #endif
            console_dev_set(klass, con);
        }

        if (sym) {
            return rb_f_send(argc, argv, con);
        }

        return con;
    }

Returns an `File` instance opened console.

If `sym` is given, it will be sent to the opened console with `args` and the result will be returned instead of the console `IO` itself.

You must require ‘io/console’ to use this method.

copy_stream(src, dst, src_length = nil, src_offset = 0) → integer
Source

    static VALUE
    rb_io_s_copy_stream(int argc, VALUE *argv, VALUE io)
    {
        VALUE src, dst, length, src_offset;
        struct copy_stream_struct st;

        MEMZERO(&st, struct copy_stream_struct, 1);

        rb_scan_args(argc, argv, "22", &src, &dst, &length, &src_offset);

        st.src = src;
        st.dst = dst;

        st.src_fptr = NULL;
        st.dst_fptr = NULL;

        if (NIL_P(length))
            st.copy_length = (rb_off_t)-1;
        else
            st.copy_length = NUM2OFFT(length);

        if (NIL_P(src_offset))
            st.src_offset = (rb_off_t)-1;
        else
            st.src_offset = NUM2OFFT(src_offset);

        rb_ensure(copy_stream_body, (VALUE)&st, copy_stream_finalize, (VALUE)&st);

        return OFFT2NUM(st.total);
    }

Copies from the given `src` to the given `dst`, returning the number of bytes copied.

- The given `src` must be one of the following:

  - The path to a readable file, from which source data is to be read.

  - An IO-like object, opened for reading and capable of responding to method `:readpartial` or method `:read`.

- The given `dst` must be one of the following:

  - The path to a writable file, to which data is to be written.

  - An IO-like object, opened for writing and capable of responding to method `:write`.

The examples here use file `t.txt` as source:

    File.read('t.txt')
    # => "First line\nSecond line\n\nThird line\nFourth line\n"
    File.read('t.txt').size # => 47

If only arguments `src` and `dst` are given, the entire source stream is copied:

    # Paths.
    IO.copy_stream('t.txt', 't.tmp')  # => 47

    # IOs (recall that a File is also an IO).
    src_io = File.open('t.txt', 'r') # => #<File:t.txt>
    dst_io = File.open('t.tmp', 'w') # => #<File:t.tmp>
    IO.copy_stream(src_io, dst_io)   # => 47
    src_io.close
    dst_io.close

With argument `src_length` a non-negative integer, no more than that many bytes are copied:

    IO.copy_stream('t.txt', 't.tmp', 10) # => 10
    File.read('t.tmp')                   # => "First line"

With argument `src_offset` also given, the source stream is read beginning at that offset:

    IO.copy_stream('t.txt', 't.tmp', 11, 11) # => 11
    IO.read('t.tmp')                         # => "Second line"

for_fd(fd, mode = 'r', **opts) → io
Source

    static VALUE
    rb_io_s_for_fd(int argc, VALUE *argv, VALUE klass)
    {
        VALUE io = rb_obj_alloc(klass);
        rb_io_initialize(argc, argv, io);
        return io;
    }

Synonym for `IO.new`.

foreach(path, sep = $/, **opts) {|line| block } → nil
foreach(path, limit, **opts) {|line| block } → nil
foreach(path, sep, limit, **opts) {|line| block } → nil
foreach(...) → an_enumerator
Source

    static VALUE
    rb_io_s_foreach(int argc, VALUE *argv, VALUE self)
    {
        VALUE opt;
        int orig_argc = argc;
        struct foreach_arg arg;
        struct getline_arg garg;

        argc = rb_scan_args(argc, argv, "12:", NULL, NULL, NULL, &opt);
        RETURN_ENUMERATOR(self, orig_argc, argv);
        extract_getline_args(argc-1, argv+1, &garg);
        open_key_args(self, argc, argv, opt, &arg);
        if (NIL_P(arg.io)) return Qnil;
        extract_getline_opts(opt, &garg);
        check_getline_args(&garg.rs, &garg.limit, garg.io = arg.io);
        return rb_ensure(io_s_foreach, (VALUE)&garg, rb_io_close, arg.io);
    }

Calls the block with each successive line read from the stream.

When called from class IO (but not subclasses of IO), this method has potential security vulnerabilities if called with untrusted input; see Command Injection.

The first argument must be a string that is the path to a file.

With only argument `path` given, parses lines from the file at the given `path`, as determined by the default line separator, and calls the block with each successive line:

    File.foreach('t.txt') {|line| p line }

Output: the same as above.

For both forms, command and path, the remaining arguments are the same.

With argument `sep` given, parses lines as determined by that line separator (see Line Separator):

    File.foreach('t.txt', 'li') {|line| p line }

Output:

    "First li"
    "ne\nSecond li"
    "ne\n\nThird li"
    "ne\nFourth li"
    "ne\n"

Each paragraph:

    File.foreach('t.txt', '') {|paragraph| p paragraph }

Output:

    "First line\nSecond line\n\n"
    "Third line\nFourth line\n"

With argument `limit` given, parses lines as determined by the default line separator and the given line-length limit (see Line Separator and Line Limit):

    File.foreach('t.txt', 7) {|line| p line }

Output:

    "First l"
    "ine\n"
    "Second "
    "line\n"
    "\n"
    "Third l"
    "ine\n"
    "Fourth l"
    "line\n"

With arguments `sep` and `limit` given, combines the two behaviors (see Line Separator and Line Limit).

Optional keyword arguments `opts` specify:

- Open Options.

- Encoding options.

- Line Options.

Returns an `Enumerator` if no block is given.

new(fd, mode = 'r', **opts) → io
Source

    static VALUE
    rb_io_initialize(int argc, VALUE *argv, VALUE io)
    {
        VALUE fnum, vmode;
        VALUE opt;

        rb_scan_args(argc, argv, "11:", &fnum, &vmode, &opt);
        return io_initialize(io, fnum, vmode, opt);
    }

Creates and returns a new IO object (file stream) from a file descriptor.

IO.new may be useful for interaction with low-level libraries. For higher-level interactions, it may be simpler to create the file stream using `File.open`.

Argument `fd` must be a valid file descriptor (integer):

    path = 't.tmp'
    fd = IO.sysopen(path) # => 3
    IO.new(fd)            # => #<IO:fd 3>

The new IO object does not inherit encoding (because the integer file descriptor does not have an encoding):

    fd = IO.sysopen('t.rus', 'rb')
    io = IO.new(fd)
    io.external_encoding # => #<Encoding:UTF-8> # Not ASCII-8BIT.

Optional argument `mode` (defaults to ‘r’) must specify a valid mode; see Access Modes:

    IO.new(fd, 'w')         # => #<IO:fd 3>
    IO.new(fd, File::WRONLY) # => #<IO:fd 3>

Optional keyword arguments `opts` specify:

- Open Options.

- Encoding options.

Examples:

    IO.new(fd, internal_encoding: nil) # => #<IO:fd 3>
    IO.new(fd, autoclose: true)        # => #<IO:fd 3>

open(fd, mode = 'r', **opts) → io
open(fd, mode = 'r', **opts) {|io| ... } → object
Source

    static VALUE
    rb_io_s_open(int argc, VALUE *argv, VALUE klass)
    {
        VALUE io = rb_class_new_instance_kw(argc, argv, klass, RB_PASS_CALLED_KEYWORDS);

        if (rb_block_given_p()) {
            return rb_ensure(rb_yield, io, io_close, io);
        }

        return io;
    }

Creates a new IO object, via `IO.new` with the given arguments.

With no block given, returns the IO object.

With a block given, calls the block with the IO object and returns the block’s value.

pipe(**opts) → [read_io, write_io]
pipe(enc, **opts) → [read_io, write_io]
pipe(ext_enc, int_enc, **opts) → [read_io, write_io]
pipe(**opts) {|read_io, write_io| ...} → object
pipe(enc, **opts) {|read_io, write_io| ...} → object
pipe(ext_enc, int_enc, **opts) {|read_io, write_io| ...} → object
Source

    static VALUE
    rb_io_s_pipe(int argc, VALUE *argv, VALUE klass)
    {
        int pipes[2], state;
        VALUE r, w, args[3], v1, v2;
        VALUE opt;
        rb_io_t *fptr, *fptr2;
        struct io_encoding_set_args ies_args;
        int fmode = 0;
        VALUE ret;

        argc = rb_scan_args(argc, argv, "02:", &v1, &v2, &opt);
        if (rb_pipe(pipes) < 0)
            rb_sys_fail(0);

        args[0] = klass;
        args[1] = INT2NUM(pipes[0]);
        args[2] = INT2FIX(O_RDONLY);
        r = rb_protect(io_new_instance, (VALUE)args, &state);
        if (state) {
            close(pipes[0]);
            close(pipes[1]);
            rb_jump_tag(state);
        }
        GetOpenFile(r, fptr);

        ies_args.fptr = fptr;
        ies_args.v1 = v1;
        ies_args.v2 = v2;
        ies_args.opt = opt;
        rb_protect(io_encoding_set_v, (VALUE)&ies_args, &state);
        if (state) {
            close(pipes[1]);
            io_close(r);
            rb_jump_tag(state);
        }

        args[1] = INT2NUM(pipes[1]);
        args[2] = INT2FIX(O_WRONLY);
        w = rb_protect(io_new_instance, (VALUE)args, &state);
        if (state) {
            close(pipes[1]);
            if (!NIL_P(r)) rb_io_close(r);
            rb_jump_tag(state);
        }
        GetOpenFile(w, fptr2);
        rb_io_synchronized(fptr2);

        extract_binmode(opt, &fmode);

        if ((fmode & FMODE_BINMODE) && NIL_P(v1)) {
            rb_io_ascii8bit_binmode(r);
            rb_io_ascii8bit_binmode(w);
        }

    #if DEFAULT_TEXTMODE
        if ((fptr->mode & FMODE_TEXTMODE) && (fmode & FMODE_BINMODE)) {
            fptr->mode &= ~FMODE_TEXTMODE;
            setmode(fptr->fd, O_BINARY);
        }
    #if RUBY_CRLF_ENVIRONMENT
        if (fptr->encs.ecflags & ECONV_DEFAULT_NEWLINE_DECORATOR) {
            fptr->encs.ecflags |= ECONV_UNIVERSAL_NEWLINE_DECORATOR;
        }
    #endif
    #endif
        fptr->mode |= fmode;
    #if DEFAULT_TEXTMODE
        if ((fptr2->mode & FMODE_TEXTMODE) && (fmode & FMODE_BINMODE)) {
            fptr2->mode &= ~FMODE_TEXTMODE;
            setmode(fptr2->fd, O_BINARY);
        }
    #endif
        fptr2->mode |= fmode;

        ret = rb_assoc_new(r, w);
        if (rb_block_given_p()) {
            VALUE rw[2];
            rw[0] = r;
            rw[1] = w;
            return rb_ensure(rb_yield, ret, pipe_pair_close, (VALUE)rw);
        }
        return ret;
    }

Creates a pair of pipe endpoints, `read_io` and `write_io`, connected to each other.

If argument `enc_string` is given, it must be a string containing one of:

- The name of the encoding to be used as the external encoding.

- The colon-separated names of two encodings to be used as the external and internal encodings.

If argument `int_enc` is given, it must be an `Encoding` object or encoding name string that specifies the internal encoding to be used; if argument `ext_enc` is also given, it must be an `Encoding` object or encoding name string that specifies the external encoding to be used.

The string read from `read_io` is tagged with the external encoding; if an internal encoding is also specified, the string is converted to, and tagged with, that encoding.

If any encoding is specified, optional hash arguments specify the conversion option.

Optional keyword arguments `opts` specify:

- Open Options.

- Encoding Options.

With no block given, returns the two endpoints in an array:

    IO.pipe # => [#<IO:fd 4>, #<IO:fd 5>]

With a block given, calls the block with the two endpoints; closes both endpoints and returns the value of the block:

    IO.pipe {|read_io, write_io| p read_io; p write_io }

Output:

    #<IO:fd 6>
    #<IO:fd 7>

Not available on all platforms.

In the example below, the two processes close the ends of the pipe that they are not using. This is not just a cosmetic nicety. The read end of a pipe will not generate an end of file condition if there are any writers with the pipe still open. In the case of the parent process, the `rd.read` will never return if it does not first issue a `wr.close`:

    rd, wr = IO.pipe

    if fork
      wr.close
      puts "Parent got: <#{rd.read}>"
      rd.close
      Process.wait
    else
      rd.close
      puts 'Sending message to parent'
      wr.write "Hi Dad"
      wr.close
    end

produces:

    Sending message to parent
    Parent got: <Hi Dad>

popen(env = {}, cmd, mode = 'r', **opts) → io
popen(env = {}, cmd, mode = 'r', **opts) {|io| ... } → object
Source

    static VALUE
    rb_io_s_popen(int argc, VALUE *argv, VALUE klass)
    {
        VALUE pname, pmode = Qnil, opt = Qnil, env = Qnil;

        if (argc > 1 && !NIL_P(opt = rb_check_hash_type(argv[argc-1]))) --argc;
        if (argc > 1 && !NIL_P(env = rb_check_hash_type(argv[0]))) --argc, ++argv;
        switch (argc) {
          case 2:
            pmode = argv[1];
          case 1:
            pname = argv[0];
            break;
          default:
            {
                int ex = !NIL_P(opt);
                rb_error_arity(argc + ex, 1 + ex, 2 + ex);
            }
        }
        return popen_finish(rb_io_popen(pname, pmode, env, opt), klass);
    }

Executes the given command `cmd` as a subprocess whose $stdin and $stdout are connected to a new stream `io`.

This method has potential security vulnerabilities if called with untrusted input; see Command Injection.

If no block is given, returns the new stream, which depending on given `mode` may be open for reading, writing, or both. The stream should be explicitly closed (eventually) to avoid resource leaks.

If a block is given, the stream is passed to the block (again, open for reading, writing, or both); when the block exits, the stream is closed, and the block’s value is assigned to global variable `$?` and returned.

Optional argument `mode` may be any valid IO mode. See Access Modes.

Required argument `cmd` determines which of the following occurs:

- The process forks.

- A specified program runs in a shell.

- A specified program runs with specified arguments.

- A specified program runs with specified arguments and a specified `argv0`.

Each of these is detailed below.

The optional hash argument `env` specifies name/value pairs that are to be added to the environment variables for the subprocess:

    IO.popen({'FOO' => 'bar'}, 'ruby', 'r+') do |pipe|
      pipe.puts 'puts ENV["FOO"]'
      pipe.close_write
      pipe.gets
    end => "bar\n"

Optional keyword arguments `opts` specify:

- Open options.

- Encoding options.

- Options for `Kernel#spawn`.

Forked Process

When argument `cmd` is the 1-character string `'-'`, causes the process to fork:

    IO.popen('-') do |pipe|
      if pipe
        $stderr.puts "In parent, child pid is #{pipe.pid}\n"
      else
        $stderr.puts "In child, pid is #{$$}\n"
      end
    end

Output:

    In parent, child pid is 26253
    In child, pid is 26253

Note that this is not supported on all platforms.

Shell Subprocess

When argument `cmd` is a single string (but not `'-'`), the program named `cmd` is run as a shell command:

    IO.popen('uname') do |pipe|
      pipe.readlines
    end

Output:

    ["Linux\n"]

Another example:

    IO.popen('/bin/sh', 'r+') do |pipe|
      pipe.puts('ls')
      pipe.close_write
      $stderr.puts pipe.readlines.size
    end

Output:

    213

Program Subprocess

When argument `cmd` is an array of strings, the program named `cmd[0]` is run with all elements of `cmd` as its arguments:

    IO.popen(['du', '..', '.']) do |pipe|
      $stderr.puts pipe.readlines.size
    end

Output:

    1111

Program Subprocess with `argv0`

When argument `cmd` is an array whose first element is a 2-element string array and whose remaining elements (if any) are strings:

- `cmd[0][0]` (the first string in the nested array) is the name of a program that is run.

- `cmd[0][1]` (the second string in the nested array) is set as the program’s `argv[0]`.

- `cmd[1..-1]` (the strings in the outer array) are the program’s arguments.

Example (sets `$0` to ‘foo’):

    IO.popen([['/bin/sh', 'foo'], '-c', 'echo $0']).read # => "foo\n"

Some Special Examples

    # Set IO encoding.
    IO.popen("nkf -e filename", :external_encoding=>"EUC-JP") {|nkf_io|
      euc_jp_string = nkf_io.read
    }

    # Merge standard output and standard error using Kernel#spawn option. See Kernel#spawn.
    IO.popen(["ls", "/", :err=>[:child, :out]]) do |io|
      ls_result_with_error = io.read
    end

    # Use mixture of spawn options and IO options.
    IO.popen(["ls", "/"], :err=>[:child, :out]) do |io|
      ls_result_with_error = io.read
    end

     f = IO.popen("uname")
     p f.readlines
     f.close
     puts "Parent is #{Process.pid}"
     IO.popen("date") {|f| puts f.gets }
     IO.popen("-") {|f| $stderr.puts "#{Process.pid} is here, f is #{f.inspect}"}
     p $?
     IO.popen(%w"sed -e s|^|<foo>| -e s&$&;zot;&", "r+") {|f|
       f.puts "bar"; f.close_write; puts f.gets
     }

Output (from last section):

    ["Linux\n"]
    Parent is 21346
    Thu Jan 15 22:41:19 JST 2009
    21346 is here, f is #<IO:fd 3>
    21352 is here, f is nil
    #<Process::Status: pid 21352 exit 0>
    <foo>bar;zot;

Raises exceptions that `IO.pipe` and `Kernel.spawn` raise.

read(path, length = nil, offset = 0, **opts) → string or nil
Source

    static VALUE
    rb_io_s_read(int argc, VALUE *argv, VALUE io)
    {
        VALUE opt, offset;
        long off;
        struct foreach_arg arg;

        argc = rb_scan_args(argc, argv, "13:", NULL, NULL, &offset, NULL, &opt);
        if (!NIL_P(offset) && (off = NUM2LONG(offset)) < 0) {
            rb_raise(rb_eArgError, "negative offset %ld given", off);
        }
        open_key_args(io, argc, argv, opt, &arg);
        if (NIL_P(arg.io)) return Qnil;
        if (!NIL_P(offset)) {
            struct seek_arg sarg;
            int state = 0;
            sarg.io = arg.io;
            sarg.offset = offset;
            sarg.mode = SEEK_SET;
            rb_protect(seek_before_access, (VALUE)&sarg, &state);
            if (state) {
                rb_io_close(arg.io);
                rb_jump_tag(state);
            }
            if (arg.argc == 2) arg.argc = 1;
        }
        return rb_ensure(io_s_read, (VALUE)&arg, rb_io_close, arg.io);
    }

Opens the stream, reads and returns some or all of its content, and closes the stream; returns `nil` if no bytes were read.

When called from class IO (but not subclasses of IO), this method has potential security vulnerabilities if called with untrusted input; see Command Injection.

The first argument must be a string that is the path to a file.

With only argument `path` given, reads in text mode and returns the entire content of the file at the given path:

    IO.read('t.txt')
    # => "First line\nSecond line\n\nThird line\nFourth line\n"

On Windows, text mode can terminate reading and leave bytes in the file unread when encountering certain special bytes. Consider using `IO.binread` if all bytes in the file should be read.

With argument `length`, returns `length` bytes if available:

    IO.read('t.txt', 7) # => "First l"
    IO.read('t.txt', 700)
    # => "First line\r\nSecond line\r\n\r\nFourth line\r\nFifth line\r\n"

With arguments `length` and `offset`, returns `length` bytes if available, beginning at the given `offset`:

    IO.read('t.txt', 10, 2)   # => "rst line\nS"
    IO.read('t.txt', 10, 200) # => nil

Optional keyword arguments `opts` specify:

- Open Options.

- Encoding options.

readlines(path, sep = $/, **opts) → array
readlines(path, limit, **opts) → array
readlines(path, sep, limit, **opts) → array
Source

    static VALUE
    rb_io_s_readlines(int argc, VALUE *argv, VALUE io)
    {
        VALUE opt;
        struct foreach_arg arg;
        struct getline_arg garg;

        argc = rb_scan_args(argc, argv, "12:", NULL, NULL, NULL, &opt);
        extract_getline_args(argc-1, argv+1, &garg);
        open_key_args(io, argc, argv, opt, &arg);
        if (NIL_P(arg.io)) return Qnil;
        extract_getline_opts(opt, &garg);
        check_getline_args(&garg.rs, &garg.limit, garg.io = arg.io);
        return rb_ensure(io_s_readlines, (VALUE)&garg, rb_io_close, arg.io);
    }

Returns an array of all lines read from the stream.

When called from class IO (but not subclasses of IO), this method has potential security vulnerabilities if called with untrusted input; see Command Injection.

The first argument must be a string that is the path to a file.

With only argument `path` given, parses lines from the file at the given `path`, as determined by the default line separator, and returns those lines in an array:

    IO.readlines('t.txt')
    # => ["First line\n", "Second line\n", "\n", "Third line\n", "Fourth line\n"]

With argument `sep` given, parses lines as determined by that line separator (see Line Separator):

    # Ordinary separator.
    IO.readlines('t.txt', 'li')
    # =>["First li", "ne\nSecond li", "ne\n\nThird li", "ne\nFourth li", "ne\n"]
    # Get-paragraphs separator.
    IO.readlines('t.txt', '')
    # => ["First line\nSecond line\n\n", "Third line\nFourth line\n"]
    # Get-all separator.
    IO.readlines('t.txt', nil)
    # => ["First line\nSecond line\n\nThird line\nFourth line\n"]

With argument `limit` given, parses lines as determined by the default line separator and the given line-length limit (see Line Separator and Line Limit:

    IO.readlines('t.txt', 7)
    # => ["First l", "ine\n", "Second ", "line\n", "\n", "Third l", "ine\n", "Fourth ", "line\n"]

With arguments `sep` and `limit` given, combines the two behaviors (see Line Separator and Line Limit).

Optional keyword arguments `opts` specify:

- Open Options.

- Encoding options.

- Line Options.

select(read_ios, write_ios = [], error_ios = [], timeout = nil) → array or nil
Source

    static VALUE
    rb_f_select(int argc, VALUE *argv, VALUE obj)
    {
        VALUE scheduler = rb_fiber_scheduler_current();
        if (scheduler != Qnil) {
            // It's optionally supported.
            VALUE result = rb_fiber_scheduler_io_selectv(scheduler, argc, argv);
            if (!UNDEF_P(result)) return result;
        }

        VALUE timeout;
        struct select_args args;
        struct timeval timerec;
        int i;

        rb_scan_args(argc, argv, "13", &args.read, &args.write, &args.except, &timeout);
        if (NIL_P(timeout)) {
            args.timeout = 0;
        }
        else {
            timerec = rb_time_interval(timeout);
            args.timeout = &timerec;
        }

        for (i = 0; i < numberof(args.fdsets); ++i)
            rb_fd_init(&args.fdsets[i]);

        return rb_ensure(select_call, (VALUE)&args, select_end, (VALUE)&args);
    }

Invokes system call select(2), which monitors multiple file descriptors, waiting until one or more of the file descriptors becomes ready for some class of I/O operation.

Not implemented on all platforms.

Each of the arguments `read_ios`, `write_ios`, and `error_ios` is an array of `IO` objects.

Argument `timeout` is a numeric value (such as integer or float) timeout interval in seconds.

The method monitors the IO objects given in all three arrays, waiting for some to be ready; returns a 3-element array whose elements are:

- An array of the objects in `read_ios` that are ready for reading.

- An array of the objects in `write_ios` that are ready for writing.

- An array of the objects in `error_ios` have pending exceptions.

If no object becomes ready within the given `timeout`, `nil` is returned.

IO.select peeks the buffer of IO objects for testing readability. If the IO buffer is not empty, IO.select immediately notifies readability. This “peek” only happens for IO objects. It does not happen for IO-like objects such as `OpenSSL::SSL::SSLSocket`.

The best way to use IO.select is invoking it after non-blocking methods such as `read_nonblock`, `write_nonblock`, etc. The methods raise an exception which is extended by `IO::WaitReadable` or `IO::WaitWritable`. The modules notify how the caller should wait with IO.select. If `IO::WaitReadable` is raised, the caller should wait for reading. If `IO::WaitWritable` is raised, the caller should wait for writing.

So, blocking read (`readpartial`) can be emulated using `read_nonblock` and IO.select as follows:

    begin
      result = io_like.read_nonblock(maxlen)
    rescue IO::WaitReadable
      IO.select([io_like])
      retry
    rescue IO::WaitWritable
      IO.select(nil, [io_like])
      retry
    end

Especially, the combination of non-blocking methods and IO.select is preferred for `IO` like objects such as `OpenSSL::SSL::SSLSocket`. It has `to_io` method to return underlying `IO` object. `IO.select` calls `to_io` to obtain the file descriptor to wait.

This means that readability notified by IO.select doesn’t mean readability from `OpenSSL::SSL::SSLSocket` object.

The most likely situation is that `OpenSSL::SSL::SSLSocket` buffers some data. IO.select doesn’t see the buffer. So IO.select can block when `OpenSSL::SSL::SSLSocket#readpartial` doesn’t block.

However, several more complicated situations exist.

SSL is a protocol which is sequence of records. The record consists of multiple bytes. So, the remote side of SSL sends a partial record, `IO.select` notifies readability but `OpenSSL::SSL::SSLSocket` cannot decrypt a byte and `OpenSSL::SSL::SSLSocket#readpartial` will block.

Also, the remote side can request SSL renegotiation which forces the local SSL engine to write some data. This means `OpenSSL::SSL::SSLSocket#readpartial` may invoke `write` system call and it can block. In such a situation, `OpenSSL::SSL::SSLSocket#read_nonblock` raises `IO::WaitWritable` instead of blocking. So, the caller should wait for ready for writability as above example.

The combination of non-blocking methods and IO.select is also useful for streams such as tty, pipe socket socket when multiple processes read from a stream.

Finally, Linux kernel developers don’t guarantee that readability of select(2) means readability of following read(2) even for a single process; see select(2)

Invoking IO.select before `IO#readpartial` works well as usual. However it is not the best way to use IO.select.

The writability notified by select(2) doesn’t show how many bytes are writable. `IO#write` method blocks until given whole string is written. So, `IO#write(two or more bytes)` can block after writability is notified by IO.select. `IO#write_nonblock` is required to avoid the blocking.

Blocking write (`write`) can be emulated using `write_nonblock` and `IO.select` as follows: `IO::WaitReadable` should also be rescued for SSL renegotiation in `OpenSSL::SSL::SSLSocket`.

    while 0 < string.bytesize
      begin
        written = io_like.write_nonblock(string)
      rescue IO::WaitReadable
        IO.select([io_like])
        retry
      rescue IO::WaitWritable
        IO.select(nil, [io_like])
        retry
      end
      string = string.byteslice(written..-1)
    end

Example:

    rp, wp = IO.pipe
    mesg = "ping "
    100.times {
      # IO.select follows IO#read.  Not the best way to use IO.select.
      rs, ws, = IO.select([rp], [wp])
      if r = rs[0]
        ret = r.read(5)
        print ret
        case ret
        when /ping/
          mesg = "pong\n"
        when /pong/
          mesg = "ping "
        end
      end
      if w = ws[0]
        w.write(mesg)
      end
    }

Output:

    ping pong
    ping pong
    ping pong
    (snipped)
    ping

sysopen(path, mode = 'r', perm = 0666) → integer
Source

    static VALUE
    rb_io_s_sysopen(int argc, VALUE *argv, VALUE _)
    {
        VALUE fname, vmode, vperm;
        VALUE intmode;
        int oflags, fd;
        mode_t perm;

        rb_scan_args(argc, argv, "12", &fname, &vmode, &vperm);
        FilePathValue(fname);

        if (NIL_P(vmode))
            oflags = O_RDONLY;
        else if (!NIL_P(intmode = rb_check_to_integer(vmode, "to_int")))
            oflags = NUM2INT(intmode);
        else {
            StringValue(vmode);
            oflags = rb_io_modestr_oflags(StringValueCStr(vmode));
        }
        if (NIL_P(vperm)) perm = 0666;
        else              perm = NUM2MODET(vperm);

        RB_GC_GUARD(fname) = rb_str_new4(fname);
        fd = rb_sysopen(fname, oflags, perm);
        return INT2NUM(fd);
    }

Opens the file at the given path with the given mode and permissions; returns the integer file descriptor.

If the file is to be readable, it must exist; if the file is to be writable and does not exist, it is created with the given permissions:

    File.write('t.tmp', '')  # => 0
    IO.sysopen('t.tmp')      # => 8
    IO.sysopen('t.tmp', 'w') # => 9

try_convert(object) → new_io or nil
Source

    static VALUE
    rb_io_s_try_convert(VALUE dummy, VALUE io)
    {
        return rb_io_check_io(io);
    }

Attempts to convert `object` into an IO object via method `to_io`; returns the new IO object if successful, or `nil` otherwise:

    IO.try_convert(STDOUT)   # => #<IO:<STDOUT>>
    IO.try_convert(ARGF)     # => #<IO:<STDIN>>
    IO.try_convert('STDOUT') # => nil

write(path, data, offset = 0, **opts) → integer
Source

    static VALUE
    rb_io_s_write(int argc, VALUE *argv, VALUE io)
    {
        return io_s_write(argc, argv, io, 0);
    }

Opens the stream, writes the given `data` to it, and closes the stream; returns the number of bytes written.

When called from class IO (but not subclasses of IO), this method has potential security vulnerabilities if called with untrusted input; see Command Injection.

The first argument must be a string that is the path to a file.

With only argument `path` given, writes the given `data` to the file at that path:

    IO.write('t.tmp', 'abc')    # => 3
    File.read('t.tmp')          # => "abc"

If `offset` is zero (the default), the file is overwritten:

    IO.write('t.tmp', 'A')      # => 1
    File.read('t.tmp')          # => "A"

If `offset` in within the file content, the file is partly overwritten:

    IO.write('t.tmp', 'abcdef') # => 3
    File.read('t.tmp')          # => "abcdef"
    # Offset within content.
    IO.write('t.tmp', '012', 2) # => 3
    File.read('t.tmp')          # => "ab012f"

If `offset` is outside the file content, the file is padded with null characters `"\u0000"`:

    IO.write('t.tmp', 'xyz', 10) # => 3
    File.read('t.tmp')           # => "ab012f\u0000\u0000\u0000\u0000xyz"

Optional keyword arguments `opts` specify:

- Open Options.

- Encoding options.

### Public Instance Methods

self << object → self
Source

    VALUE
    rb_io_addstr(VALUE io, VALUE str)
    {
        rb_io_write(io, str);
        return io;
    }

Writes the given `object` to `self`, which must be opened for writing (see Access Modes); returns `self`; if `object` is not a string, it is converted via method `to_s`:

    $stdout << 'Hello' << ', ' << 'World!' << "\n"
    $stdout << 'foo' << :bar << 2 << "\n"

Output:

    Hello, World!
    foobar2

advise(advice, offset = 0, len = 0) → nil
Source

    static VALUE
    rb_io_advise(int argc, VALUE *argv, VALUE io)
    {
        VALUE advice, offset, len;
        rb_off_t off, l;
        rb_io_t *fptr;

        rb_scan_args(argc, argv, "12", &advice, &offset, &len);
        advice_arg_check(advice);

        io = GetWriteIO(io);
        GetOpenFile(io, fptr);

        off = NIL_P(offset) ? 0 : NUM2OFFT(offset);
        l   = NIL_P(len)    ? 0 : NUM2OFFT(len);

    #ifdef HAVE_POSIX_FADVISE
        return do_io_advise(fptr, advice, off, l);
    #else
        ((void)off, (void)l);       /* Ignore all hint */
        return Qnil;
    #endif
    }

Invokes Posix system call posix_fadvise(2), which announces an intention to access data from the current file in a particular manner.

The arguments and results are platform-dependent.

The relevant data is specified by:

- `offset`: The offset of the first byte of data.

- `len`: The number of bytes to be accessed; if `len` is zero, or is larger than the number of bytes remaining, all remaining bytes will be accessed.

Argument `advice` is one of the following symbols:

- `:normal`: The application has no advice to give about its access pattern for the specified data. If no advice is given for an open file, this is the default assumption.

- `:sequential`: The application expects to access the specified data sequentially (with lower offsets read before higher ones).

- `:random`: The specified data will be accessed in random order.

- `:noreuse`: The specified data will be accessed only once.

- `:willneed`: The specified data will be accessed in the near future.

- `:dontneed`: The specified data will not be accessed in the near future.

Not implemented on all platforms.

autoclose = bool → true or false
Source

    static VALUE
    rb_io_set_autoclose(VALUE io, VALUE autoclose)
    {
        rb_io_t *fptr;
        GetOpenFile(io, fptr);
        if (!RTEST(autoclose))
            fptr->mode |= FMODE_EXTERNAL;
        else
            fptr->mode &= ~FMODE_EXTERNAL;
        return autoclose;
    }

Sets auto-close flag.

    f = File.open(File::NULL)
    IO.for_fd(f.fileno).close
    f.gets # raises Errno::EBADF

    f = File.open(File::NULL)
    g = IO.for_fd(f.fileno)
    g.autoclose = false
    g.close
    f.gets # won't cause Errno::EBADF

autoclose? → true or false
Source

    static VALUE
    rb_io_autoclose_p(VALUE io)
    {
        rb_io_t *fptr = RFILE(io)->fptr;
        rb_io_check_closed(fptr);
        return RBOOL(!(fptr->mode & FMODE_EXTERNAL));
    }

Returns `true` if the underlying file descriptor of ios will be closed at its finalization or at calling `close`, otherwise `false`.

beep
Source

    static VALUE
    console_beep(VALUE io)
    {
    #ifdef _WIN32
        MessageBeep(0);
    #else
        int fd = GetWriteFD(io);
        if (write(fd, "\a", 1) < 0) sys_fail(io);
    #endif
        return io;
    }

Beeps on the output console.

You must require ‘io/console’ to use this method.

binmode → self
Source

    static VALUE
    rb_io_binmode_m(VALUE io)
    {
        VALUE write_io;

        rb_io_ascii8bit_binmode(io);

        write_io = GetWriteIO(io);
        if (write_io != io)
            rb_io_ascii8bit_binmode(write_io);
        return io;
    }

Sets the stream’s data mode as binary (see Data Mode).

A stream’s data mode may not be changed from binary to text.

binmode? → true or false
Source

    static VALUE
    rb_io_binmode_p(VALUE io)
    {
        rb_io_t *fptr;
        GetOpenFile(io, fptr);
        return RBOOL(fptr->mode & FMODE_BINMODE);
    }

Returns `true` if the stream is on binary mode, `false` otherwise. See Data Mode.

check_winsize_changed { ... } → io
Source

    static VALUE
    console_check_winsize_changed(VALUE io)
    {
        HANDLE h;
        DWORD num;

        h = (HANDLE)rb_w32_get_osfhandle(GetReadFD(io));
        while (GetNumberOfConsoleInputEvents(h, &num) && num > 0) {
            INPUT_RECORD rec;
            if (ReadConsoleInput(h, &rec, 1, &num)) {
                if (rec.EventType == WINDOW_BUFFER_SIZE_EVENT) {
                    rb_yield(Qnil);
                }
            }
        }
        return io;
    }

Yields while console input events are queued.

This method is Windows only.

You must require ‘io/console’ to use this method.

clear_screen → io
Source

    static VALUE
    console_clear_screen(VALUE io)
    {
        console_erase_screen(io, INT2FIX(2));
        console_goto(io, INT2FIX(0), INT2FIX(0));
        return io;
    }

Clears the entire screen and moves the cursor top-left corner.

You must require ‘io/console’ to use this method.

close → nil
Source

    static VALUE
    rb_io_close_m(VALUE io)
    {
        rb_io_t *fptr = rb_io_get_fptr(io);
        if (fptr->fd < 0) {
            return Qnil;
        }
        rb_io_close(io);
        return Qnil;
    }

Closes the stream for both reading and writing if open for either or both; returns `nil`. See Open and Closed Streams.

If the stream is open for writing, flushes any buffered writes to the operating system before closing.

If the stream was opened by `IO.popen`, sets global variable `$?` (child exit status).

It is not an error to close an `IO` object that has already been closed. It just returns nil.

Example:

    IO.popen('ruby', 'r+') do |pipe|
      puts pipe.closed?
      pipe.close
      puts $?
      puts pipe.closed?
    end

Output:

    false
    pid 13760 exit 0
    true

Related: `IO#close_read`, `IO#close_write`, `IO#closed?`.

close_on_exec = bool → true or false
Source

    static VALUE
    rb_io_set_close_on_exec(VALUE io, VALUE arg)
    {
        int flag = RTEST(arg) ? FD_CLOEXEC : 0;
        rb_io_t *fptr;
        VALUE write_io;
        int fd, ret;

        write_io = GetWriteIO(io);
        if (io != write_io) {
            GetOpenFile(write_io, fptr);
            if (fptr && 0 <= (fd = fptr->fd)) {
                if ((ret = fcntl(fptr->fd, F_GETFD)) == -1) rb_sys_fail_path(fptr->pathv);
                if ((ret & FD_CLOEXEC) != flag) {
                    ret = (ret & ~FD_CLOEXEC) | flag;
                    ret = fcntl(fd, F_SETFD, ret);
                    if (ret != 0) rb_sys_fail_path(fptr->pathv);
                }
            }

        }

        GetOpenFile(io, fptr);
        if (fptr && 0 <= (fd = fptr->fd)) {
            if ((ret = fcntl(fd, F_GETFD)) == -1) rb_sys_fail_path(fptr->pathv);
            if ((ret & FD_CLOEXEC) != flag) {
                ret = (ret & ~FD_CLOEXEC) | flag;
                ret = fcntl(fd, F_SETFD, ret);
                if (ret != 0) rb_sys_fail_path(fptr->pathv);
            }
        }
        return Qnil;
    }

Sets a close-on-exec flag.

    f = File.open(File::NULL)
    f.close_on_exec = true
    system("cat", "/proc/self/fd/#{f.fileno}") # cat: /proc/self/fd/3: No such file or directory
    f.closed?                #=> false

Ruby sets close-on-exec flags of all file descriptors by default since Ruby 2.0.0. So you don’t need to set by yourself. Also, unsetting a close-on-exec flag can cause file descriptor leak if another thread use fork() and exec() (via system() method for example). If you really needs file descriptor inheritance to child process, use spawn()‘s argument such as fd=>fd.

close_on_exec? → true or false
Source

    static VALUE
    rb_io_close_on_exec_p(VALUE io)
    {
        rb_io_t *fptr;
        VALUE write_io;
        int fd, ret;

        write_io = GetWriteIO(io);
        if (io != write_io) {
            GetOpenFile(write_io, fptr);
            if (fptr && 0 <= (fd = fptr->fd)) {
                if ((ret = fcntl(fd, F_GETFD)) == -1) rb_sys_fail_path(fptr->pathv);
                if (!(ret & FD_CLOEXEC)) return Qfalse;
            }
        }

        GetOpenFile(io, fptr);
        if (fptr && 0 <= (fd = fptr->fd)) {
            if ((ret = fcntl(fd, F_GETFD)) == -1) rb_sys_fail_path(fptr->pathv);
            if (!(ret & FD_CLOEXEC)) return Qfalse;
        }
        return Qtrue;
    }

Returns `true` if the stream will be closed on exec, `false` otherwise:

    f = File.open('t.txt')
    f.close_on_exec? # => true
    f.close_on_exec = false
    f.close_on_exec? # => false
    f.close

close_read → nil
Source

    static VALUE
    rb_io_close_read(VALUE io)
    {
        rb_io_t *fptr;
        VALUE write_io;

        fptr = rb_io_get_fptr(rb_io_taint_check(io));
        if (fptr->fd < 0) return Qnil;
        if (is_socket(fptr->fd, fptr->pathv)) {
    #ifndef SHUT_RD
    # define SHUT_RD 0
    #endif
            if (shutdown(fptr->fd, SHUT_RD) < 0)
                rb_sys_fail_path(fptr->pathv);
            fptr->mode &= ~FMODE_READABLE;
            if (!(fptr->mode & FMODE_WRITABLE))
                return rb_io_close(io);
            return Qnil;
        }

        write_io = GetWriteIO(io);
        if (io != write_io) {
            rb_io_t *wfptr;
            wfptr = rb_io_get_fptr(rb_io_taint_check(write_io));
            wfptr->pid = fptr->pid;
            fptr->pid = 0;
            RFILE(io)->fptr = wfptr;
            /* bind to write_io temporarily to get rid of memory/fd leak */
            fptr->tied_io_for_writing = 0;
            RFILE(write_io)->fptr = fptr;
            rb_io_fptr_cleanup(fptr, FALSE);
            /* should not finalize fptr because another thread may be reading it */
            return Qnil;
        }

        if ((fptr->mode & (FMODE_DUPLEX|FMODE_WRITABLE)) == FMODE_WRITABLE) {
            rb_raise(rb_eIOError, "closing non-duplex IO for reading");
        }
        return rb_io_close(io);
    }

Closes the stream for reading if open for reading; returns `nil`. See Open and Closed Streams.

If the stream was opened by `IO.popen` and is also closed for writing, sets global variable `$?` (child exit status).

Example:

    IO.popen('ruby', 'r+') do |pipe|
      puts pipe.closed?
      pipe.close_write
      puts pipe.closed?
      pipe.close_read
      puts $?
      puts pipe.closed?
    end

Output:

    false
    false
    pid 14748 exit 0
    true

Related: `IO#close`, `IO#close_write`, `IO#closed?`.

close_write → nil
Source

    static VALUE
    rb_io_close_write(VALUE io)
    {
        rb_io_t *fptr;
        VALUE write_io;

        write_io = GetWriteIO(io);
        fptr = rb_io_get_fptr(rb_io_taint_check(write_io));
        if (fptr->fd < 0) return Qnil;
        if (is_socket(fptr->fd, fptr->pathv)) {
    #ifndef SHUT_WR
    # define SHUT_WR 1
    #endif
            if (shutdown(fptr->fd, SHUT_WR) < 0)
                rb_sys_fail_path(fptr->pathv);
            fptr->mode &= ~FMODE_WRITABLE;
            if (!(fptr->mode & FMODE_READABLE))
                return rb_io_close(write_io);
            return Qnil;
        }

        if ((fptr->mode & (FMODE_DUPLEX|FMODE_READABLE)) == FMODE_READABLE) {
            rb_raise(rb_eIOError, "closing non-duplex IO for writing");
        }

        if (io != write_io) {
            fptr = rb_io_get_fptr(rb_io_taint_check(io));
            fptr->tied_io_for_writing = 0;
        }
        rb_io_close(write_io);
        return Qnil;
    }

Closes the stream for writing if open for writing; returns `nil`. See Open and Closed Streams.

Flushes any buffered writes to the operating system before closing.

If the stream was opened by `IO.popen` and is also closed for reading, sets global variable `$?` (child exit status).

    IO.popen('ruby', 'r+') do |pipe|
      puts pipe.closed?
      pipe.close_read
      puts pipe.closed?
      pipe.close_write
      puts $?
      puts pipe.closed?
    end

Output:

    false
    false
    pid 15044 exit 0
    true

Related: `IO#close`, `IO#close_read`, `IO#closed?`.

closed? → true or false
Source

    VALUE
    rb_io_closed_p(VALUE io)
    {
        rb_io_t *fptr;
        VALUE write_io;
        rb_io_t *write_fptr;

        write_io = GetWriteIO(io);
        if (io != write_io) {
            write_fptr = RFILE(write_io)->fptr;
            if (write_fptr && 0 <= write_fptr->fd) {
                return Qfalse;
            }
        }

        fptr = rb_io_get_fptr(io);
        return RBOOL(0 > fptr->fd);
    }

Returns `true` if the stream is closed for both reading and writing, `false` otherwise. See Open and Closed Streams.

    IO.popen('ruby', 'r+') do |pipe|
      puts pipe.closed?
      pipe.close_read
      puts pipe.closed?
      pipe.close_write
      puts pipe.closed?
    end

Output:

    false
    false
    true

Related: `IO#close_read`, `IO#close_write`, `IO#close`.

console_mode → mode
Source

    static VALUE
    console_conmode_get(VALUE io)
    {
        conmode t;
        int fd = GetReadFD(io);

        if (!getattr(fd, &t)) sys_fail(io);

        return conmode_new(cConmode, &t);
    }

Returns a data represents the current console mode.

You must require ‘io/console’ to use this method.

console_mode = mode
Source

    static VALUE
    console_conmode_set(VALUE io, VALUE mode)
    {
        conmode *t, r;
        int fd = GetReadFD(io);

        TypedData_Get_Struct(mode, conmode, &conmode_type, t);
        r = *t;

        if (!setattr(fd, &r)) sys_fail(io);

        return mode;
    }

Sets the console mode to `mode`.

You must require ‘io/console’ to use this method.

cooked {|io| }
Source

    static VALUE
    console_cooked(VALUE io)
    {
        return ttymode(io, rb_yield, io, set_cookedmode, NULL);
    }

Yields `self` within cooked mode.

    STDIN.cooked(&:gets)

will read and return a line with echo back and line editing.

You must require ‘io/console’ to use this method.

cooked!
Source

    static VALUE
    console_set_cooked(VALUE io)
    {
        conmode t;
        int fd = GetReadFD(io);
        if (!getattr(fd, &t)) sys_fail(io);
        set_cookedmode(&t, NULL);
        if (!setattr(fd, &t)) sys_fail(io);
        return io;
    }

Enables cooked mode.

If the terminal mode needs to be back, use io.cooked { … }.

You must require ‘io/console’ to use this method.

cursor → [row, column]
Source

    static VALUE
    console_cursor_pos(VALUE io)
    {
    #ifdef _WIN32
        rb_console_size_t ws;
        int fd = GetWriteFD(io);
        if (!GetConsoleScreenBufferInfo((HANDLE)rb_w32_get_osfhandle(fd), &ws)) {
            rb_syserr_fail(LAST_ERROR, 0);
        }
        return rb_assoc_new(UINT2NUM(ws.dwCursorPosition.Y), UINT2NUM(ws.dwCursorPosition.X));
    #else
        static const struct query_args query = {"\033[6n", 0};
        VALUE resp = console_vt_response(0, 0, io, &query);
        VALUE row, column, term;
        unsigned int r, c;
        if (!RB_TYPE_P(resp, T_ARRAY) || RARRAY_LEN(resp) != 3) return Qnil;
        term = RARRAY_AREF(resp, 2);
        if (!RB_TYPE_P(term, T_STRING) || RSTRING_LEN(term) != 1) return Qnil;
        if (RSTRING_PTR(term)[0] != 'R') return Qnil;
        row = RARRAY_AREF(resp, 0);
        column = RARRAY_AREF(resp, 1);
        rb_ary_resize(resp, 2);
        r = NUM2UINT(row) - 1;
        c = NUM2UINT(column) - 1;
        RARRAY_ASET(resp, 0, INT2NUM(r));
        RARRAY_ASET(resp, 1, INT2NUM(c));
        return resp;
    #endif
    }

Returns the current cursor position as a two-element array of integers (row, column)

    io.cursor # => [3, 5]

You must require ‘io/console’ to use this method.

cursor = [line, column] → io
Source

    static VALUE
    console_cursor_set(VALUE io, VALUE cpos)
    {
        cpos = rb_convert_type(cpos, T_ARRAY, "Array", "to_ary");
        if (RARRAY_LEN(cpos) != 2) rb_raise(rb_eArgError, "expected 2D coordinate");
        return console_goto(io, RARRAY_AREF(cpos, 0), RARRAY_AREF(cpos, 1));
    }

Same as `io.goto(line, column)`

See `IO#goto`.

You must require ‘io/console’ to use this method.

cursor_down(n) → io
Source

    static VALUE
    console_cursor_down(VALUE io, VALUE val)
    {
        return console_move(io, +NUM2INT(val), 0);
    }

Moves the cursor down `n` lines.

You must require ‘io/console’ to use this method.

cursor_left(n) → io
Source

    static VALUE
    console_cursor_left(VALUE io, VALUE val)
    {
        return console_move(io, 0, -NUM2INT(val));
    }

Moves the cursor left `n` columns.

You must require ‘io/console’ to use this method.

cursor_right(n) → io
Source

    static VALUE
    console_cursor_right(VALUE io, VALUE val)
    {
        return console_move(io, 0, +NUM2INT(val));
    }

Moves the cursor right `n` columns.

You must require ‘io/console’ to use this method.

cursor_up(n) → io
Source

    static VALUE
    console_cursor_up(VALUE io, VALUE val)
    {
        return console_move(io, -NUM2INT(val), 0);
    }

Moves the cursor up `n` lines.

You must require ‘io/console’ to use this method.

each
Source
Also aliased as: each_line
each_byte {|byte| ... } → self
each_byte → enumerator
Source

    static VALUE
    rb_io_each_byte(VALUE io)
    {
        rb_io_t *fptr;

        RETURN_ENUMERATOR(io, 0, 0);
        GetOpenFile(io, fptr);

        do {
            while (fptr->rbuf.len > 0) {
                char *p = fptr->rbuf.ptr + fptr->rbuf.off++;
                fptr->rbuf.len--;
                rb_yield(INT2FIX(*p & 0xff));
                rb_io_check_byte_readable(fptr);
                errno = 0;
            }
            READ_CHECK(fptr);
        } while (io_fillbuf(fptr) >= 0);
        return io;
    }

Calls the given block with each byte (0..255) in the stream; returns `self`. See Byte IO.

    f = File.new('t.rus')
    a = []
    f.each_byte {|b| a << b }
    a # => [209, 130, 208, 181, 209, 129, 209, 130]
    f.close

Returns an `Enumerator` if no block is given.

Related: `IO#each_char`, `IO#each_codepoint`.

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

    static VALUE
    rb_io_each_char(VALUE io)
    {
        rb_io_t *fptr;
        rb_encoding *enc;
        VALUE c;

        RETURN_ENUMERATOR(io, 0, 0);
        GetOpenFile(io, fptr);
        rb_io_check_char_readable(fptr);

        enc = io_input_encoding(fptr);
        READ_CHECK(fptr);
        while (!NIL_P(c = io_getc(fptr, enc))) {
            rb_yield(c);
        }
        return io;
    }

Calls the given block with each character in the stream; returns `self`. See Character IO.

    f = File.new('t.rus')
    a = []
    f.each_char {|c| a << c.ord }
    a # => [1090, 1077, 1089, 1090]
    f.close

Returns an `Enumerator` if no block is given.

Related: `IO#each_byte`, `IO#each_codepoint`.

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

    static VALUE
    rb_io_each_codepoint(VALUE io)
    {
        rb_io_t *fptr;
        rb_encoding *enc;
        unsigned int c;
        int r, n;

        RETURN_ENUMERATOR(io, 0, 0);
        GetOpenFile(io, fptr);
        rb_io_check_char_readable(fptr);

        READ_CHECK(fptr);
        if (NEED_READCONV(fptr)) {
            SET_BINARY_MODE(fptr);
            r = 1;          /* no invalid char yet */
            for (;;) {
                make_readconv(fptr, 0);
                for (;;) {
                    if (fptr->cbuf.len) {
                        if (fptr->encs.enc)
                            r = rb_enc_precise_mbclen(fptr->cbuf.ptr+fptr->cbuf.off,
                                                      fptr->cbuf.ptr+fptr->cbuf.off+fptr->cbuf.len,
                                                      fptr->encs.enc);
                        else
                            r = ONIGENC_CONSTRUCT_MBCLEN_CHARFOUND(1);
                        if (!MBCLEN_NEEDMORE_P(r))
                            break;
                        if (fptr->cbuf.len == fptr->cbuf.capa) {
                            rb_raise(rb_eIOError, "too long character");
                        }
                    }
                    if (more_char(fptr) == MORE_CHAR_FINISHED) {
                        clear_readconv(fptr);
                        if (!MBCLEN_CHARFOUND_P(r)) {
                            enc = fptr->encs.enc;
                            goto invalid;
                        }
                        return io;
                    }
                }
                if (MBCLEN_INVALID_P(r)) {
                    enc = fptr->encs.enc;
                    goto invalid;
                }
                n = MBCLEN_CHARFOUND_LEN(r);
                if (fptr->encs.enc) {
                    c = rb_enc_codepoint(fptr->cbuf.ptr+fptr->cbuf.off,
                                         fptr->cbuf.ptr+fptr->cbuf.off+fptr->cbuf.len,
                                         fptr->encs.enc);
                }
                else {
                    c = (unsigned char)fptr->cbuf.ptr[fptr->cbuf.off];
                }
                fptr->cbuf.off += n;
                fptr->cbuf.len -= n;
                rb_yield(UINT2NUM(c));
                rb_io_check_byte_readable(fptr);
            }
        }
        NEED_NEWLINE_DECORATOR_ON_READ_CHECK(fptr);
        enc = io_input_encoding(fptr);
        while (io_fillbuf(fptr) >= 0) {
            r = rb_enc_precise_mbclen(fptr->rbuf.ptr+fptr->rbuf.off,
                                      fptr->rbuf.ptr+fptr->rbuf.off+fptr->rbuf.len, enc);
            if (MBCLEN_CHARFOUND_P(r) &&
                (n = MBCLEN_CHARFOUND_LEN(r)) <= fptr->rbuf.len) {
                c = rb_enc_codepoint(fptr->rbuf.ptr+fptr->rbuf.off,
                                     fptr->rbuf.ptr+fptr->rbuf.off+fptr->rbuf.len, enc);
                fptr->rbuf.off += n;
                fptr->rbuf.len -= n;
                rb_yield(UINT2NUM(c));
            }
            else if (MBCLEN_INVALID_P(r)) {
                goto invalid;
            }
            else if (MBCLEN_NEEDMORE_P(r)) {
                char cbuf[8], *p = cbuf;
                int more = MBCLEN_NEEDMORE_LEN(r);
                if (more > numberof(cbuf)) goto invalid;
                more += n = fptr->rbuf.len;
                if (more > numberof(cbuf)) goto invalid;
                while ((n = (int)read_buffered_data(p, more, fptr)) > 0 &&
                       (p += n, (more -= n) > 0)) {
                    if (io_fillbuf(fptr) < 0) goto invalid;
                    if ((n = fptr->rbuf.len) > more) n = more;
                }
                r = rb_enc_precise_mbclen(cbuf, p, enc);
                if (!MBCLEN_CHARFOUND_P(r)) goto invalid;
                c = rb_enc_codepoint(cbuf, p, enc);
                rb_yield(UINT2NUM(c));
            }
            else {
                continue;
            }
            rb_io_check_byte_readable(fptr);
        }
        return io;

      invalid:
        rb_raise(rb_eArgError, "invalid byte sequence in %s", rb_enc_name(enc));
        UNREACHABLE_RETURN(Qundef);
    }

Calls the given block with each codepoint in the stream; returns `self`:

    f = File.new('t.rus')
    a = []
    f.each_codepoint {|c| a << c }
    a # => [1090, 1077, 1089, 1090]
    f.close

Returns an `Enumerator` if no block is given.

Related: `IO#each_byte`, `IO#each_char`.

each_line(sep = $/, chomp: false) {|line| ... } → self
each_line(limit, chomp: false) {|line| ... } → self
each_line(sep, limit, chomp: false) {|line| ... } → self
each_line → enumerator

Calls the block with each remaining line read from the stream; returns `self`. Does nothing if already at end-of-stream; See Line IO.

With no arguments given, reads lines as determined by line separator `$/`:

    f = File.new('t.txt')
    f.each_line {|line| p line }
    f.each_line {|line| fail 'Cannot happen' }
    f.close

Output:

    "First line\n"
    "Second line\n"
    "\n"
    "Fourth line\n"
    "Fifth line\n"

With only string argument `sep` given, reads lines as determined by line separator `sep`; see Line Separator:

    f = File.new('t.txt')
    f.each_line('li') {|line| p line }
    f.close

Output:

    "First li"
    "ne\nSecond li"
    "ne\n\nFourth li"
    "ne\nFifth li"
    "ne\n"

The two special values for `sep` are honored:

    f = File.new('t.txt')
    # Get all into one string.
    f.each_line(nil) {|line| p line }
    f.close

Output:

    "First line\nSecond line\n\nFourth line\nFifth line\n"

    f.rewind
    # Get paragraphs (up to two line separators).
    f.each_line('') {|line| p line }

Output:

    "First line\nSecond line\n\n"
    "Fourth line\nFifth line\n"

With only integer argument `limit` given, limits the number of bytes in each line; see Line Limit:

    f = File.new('t.txt')
    f.each_line(8) {|line| p line }
    f.close

Output:

    "First li"
    "ne\n"
    "Second l"
    "ine\n"
    "\n"
    "Fourth l"
    "ine\n"
    "Fifth li"
    "ne\n"

With arguments `sep` and `limit` given, combines the two behaviors (see Line Separator and Line Limit).

Optional keyword argument `chomp` specifies whether line separators are to be omitted:

    f = File.new('t.txt')
    f.each_line(chomp: true) {|line| p line }
    f.close

Output:

    "First line"
    "Second line"
    ""
    "Fourth line"
    "Fifth line"

Returns an `Enumerator` if no block is given.

Alias for: each
echo = flag
Source

    static VALUE
    console_set_echo(VALUE io, VALUE f)
    {
        conmode t;
        int fd = GetReadFD(io);

        if (!getattr(fd, &t)) sys_fail(io);

        if (RTEST(f))
            set_echo(&t, NULL);
        else
            set_noecho(&t, NULL);

        if (!setattr(fd, &t)) sys_fail(io);

        return io;
    }

Enables/disables echo back. On some platforms, all combinations of this flags and raw/cooked mode may not be valid.

You must require ‘io/console’ to use this method.

echo? → true or false
Source

    static VALUE
    console_echo_p(VALUE io)
    {
        conmode t;
        int fd = GetReadFD(io);

        if (!getattr(fd, &t)) sys_fail(io);
        return echo_p(&t) ? Qtrue : Qfalse;
    }

Returns `true` if echo back is enabled.

You must require ‘io/console’ to use this method.

eof → true or false
Source

    VALUE
    rb_io_eof(VALUE io)
    {
        rb_io_t *fptr;

        GetOpenFile(io, fptr);
        rb_io_check_char_readable(fptr);

        if (READ_CHAR_PENDING(fptr)) return Qfalse;
        if (READ_DATA_PENDING(fptr)) return Qfalse;
        READ_CHECK(fptr);
    #if RUBY_CRLF_ENVIRONMENT
        if (!NEED_READCONV(fptr) && NEED_NEWLINE_DECORATOR_ON_READ(fptr)) {
            return RBOOL(eof(fptr->fd));
        }
    #endif
        return RBOOL(io_fillbuf(fptr) < 0);
    }

Returns `true` if the stream is positioned at its end, `false` otherwise; see Position:

    f = File.open('t.txt')
    f.eof           # => false
    f.seek(0, :END) # => 0
    f.eof           # => true
    f.close

Raises an exception unless the stream is opened for reading; see Mode.

If `self` is a stream such as pipe or socket, this method blocks until the other end sends some data or closes it:

    r, w = IO.pipe
    Thread.new { sleep 1; w.close }
    r.eof? # => true # After 1-second wait.

    r, w = IO.pipe
    Thread.new { sleep 1; w.puts "a" }
    r.eof?  # => false # After 1-second wait.

    r, w = IO.pipe
    r.eof?  # blocks forever

Note that this method reads data to the input byte buffer. So `IO#sysread` may not behave as you intend with `IO#eof?`, unless you call `IO#rewind` first (which is not available for some streams).

Also aliased as: eof?
eof?
Alias for: eof
erase_line(mode) → io
Source

    static VALUE
    console_erase_line(VALUE io, VALUE val)
    {
        int mode = mode_in_range(val, 2, "line erase");
    #ifdef _WIN32
        HANDLE h;
        rb_console_size_t ws;
        COORD *pos = &ws.dwCursorPosition;
        DWORD w;

        h = (HANDLE)rb_w32_get_osfhandle(GetWriteFD(io));
        if (!GetConsoleScreenBufferInfo(h, &ws)) {
            rb_syserr_fail(LAST_ERROR, 0);
        }
        w = winsize_col(&ws);
        switch (mode) {
          case 0:                   /* after cursor */
            w -= pos->X;
            break;
          case 1:                   /* before *and* cursor */
            w = pos->X + 1;
            pos->X = 0;
            break;
          case 2:                   /* entire line */
            pos->X = 0;
            break;
        }
        constat_clear(h, ws.wAttributes, w, *pos);
        return io;
    #else
        rb_io_write(io, rb_sprintf(CSI "%dK", mode));
    #endif
        return io;
    }

Erases the line at the cursor corresponding to `mode`. `mode` may be either: 0: after cursor 1: before and cursor 2: entire line

You must require ‘io/console’ to use this method.

erase_screen(mode) → io
Source

    static VALUE
    console_erase_screen(VALUE io, VALUE val)
    {
        int mode = mode_in_range(val, 3, "screen erase");
    #ifdef _WIN32
        HANDLE h;
        rb_console_size_t ws;
        COORD *pos = &ws.dwCursorPosition;
        DWORD w;

        h = (HANDLE)rb_w32_get_osfhandle(GetWriteFD(io));
        if (!GetConsoleScreenBufferInfo(h, &ws)) {
            rb_syserr_fail(LAST_ERROR, 0);
        }
        w = winsize_col(&ws);
        switch (mode) {
          case 0:   /* erase after cursor */
            w = (w * (ws.srWindow.Bottom - pos->Y + 1) - pos->X);
            break;
          case 1:   /* erase before *and* cursor */
            w = (w * (pos->Y - ws.srWindow.Top) + pos->X + 1);
            pos->X = 0;
            pos->Y = ws.srWindow.Top;
            break;
          case 2:   /* erase entire screen */
            w = (w * winsize_row(&ws));
            pos->X = 0;
            pos->Y = ws.srWindow.Top;
            break;
          case 3:   /* erase entire screen */
            w = (w * ws.dwSize.Y);
            pos->X = 0;
            pos->Y = 0;
            break;
        }
        constat_clear(h, ws.wAttributes, w, *pos);
    #else
        rb_io_write(io, rb_sprintf(CSI "%dJ", mode));
    #endif
        return io;
    }

Erases the screen at the cursor corresponding to `mode`. `mode` may be either: 0: after cursor 1: before and cursor 2: entire screen

You must require ‘io/console’ to use this method.

IO#expect(pattern,timeout=9999999) → Array
IO#expect(pattern,timeout=9999999) { |result| ... } → nil
Source

    # File ext/pty/lib/expect.rb, line 33
    def expect(pat,timeout=9999999)
      buf = ''.dup
      case pat
      when String
        e_pat = Regexp.new(Regexp.quote(pat))
      when Regexp
        e_pat = pat
      else
        raise TypeError, "unsupported pattern class: #{pat.class}"
      end
      @unusedBuf ||= ''
      while true
        if not @unusedBuf.empty?
          c = @unusedBuf.slice!(0)
        elsif !IO.select([self],nil,nil,timeout) or eof? then
          result = nil
          @unusedBuf = buf
          break
        else
          c = getc
        end
        buf << c
        if $expect_verbose
          STDOUT.print c
          STDOUT.flush
        end
        if mat=e_pat.match(buf) then
          result = [buf,*mat.captures]
          break
        end
      end
      if block_given? then
        yield result
      else
        return result
      end
      nil
    end

The `expect` library adds instance method `IO#expect`, which is similar to the TCL expect extension.

To use this method, you must require `expect`:

    require 'expect'

Reads from the `IO` until the given `pattern` matches or the `timeout` is over.

It returns an array with the read buffer, followed by the matches. If a block is given, the result is yielded to the block and returns nil.

When called without a block, it waits until the input that matches the given `pattern` is obtained from the `IO` or the time specified as the timeout passes. An array is returned when the pattern is obtained from the `IO`. The first element of the array is the entire string obtained from the `IO` until the pattern matches, followed by elements indicating which the pattern which matched to the anchor in the regular expression.

The optional timeout parameter defines, in seconds, the total time to wait for the pattern. If the timeout expires or eof is found, nil is returned or yielded. However, the buffer in a timeout session is kept for the next expect call. The default timeout is 9999999 seconds.

external_encoding → encoding or nil
Source

    static VALUE
    rb_io_external_encoding(VALUE io)
    {
        rb_io_t *fptr = RFILE(rb_io_taint_check(io))->fptr;

        if (fptr->encs.enc2) {
            return rb_enc_from_encoding(fptr->encs.enc2);
        }
        if (fptr->mode & FMODE_WRITABLE) {
            if (fptr->encs.enc)
                return rb_enc_from_encoding(fptr->encs.enc);
            return Qnil;
        }
        return rb_enc_from_encoding(io_read_encoding(fptr));
    }

Returns the `Encoding` object that represents the encoding of the stream, or `nil` if the stream is in write mode and no encoding is specified.

See Encodings.

fcntl(integer_cmd, argument) → integer
Source

    static VALUE
    rb_io_fcntl(int argc, VALUE *argv, VALUE io)
    {
        VALUE req, arg;

        rb_scan_args(argc, argv, "11", &req, &arg);
        return rb_fcntl(io, req, arg);
    }

Invokes Posix system call fcntl(2), which provides a mechanism for issuing low-level commands to control or query a file-oriented I/O stream. Arguments and results are platform dependent.

If `argument` is a number, its value is passed directly; if it is a string, it is interpreted as a binary sequence of bytes. (`Array#pack` might be a useful way to build this string.)

Not implemented on all platforms.

fdatasync → 0
Source

    static VALUE
    rb_io_fdatasync(VALUE io)
    {
        rb_io_t *fptr;

        io = GetWriteIO(io);
        GetOpenFile(io, fptr);

        if (io_fflush(fptr) < 0)
            rb_sys_fail_on_write(fptr);

        if ((int)rb_io_blocking_region(fptr, nogvl_fdatasync, fptr) == 0)
            return INT2FIX(0);

        /* fall back */
        return rb_io_fsync(io);
    }

Immediately writes to disk all data buffered in the stream, via the operating system’s: `fdatasync(2)`, if supported, otherwise via `fsync(2)`, if supported; otherwise raises an exception.

fileno → integer
Source

    static VALUE
    rb_io_fileno(VALUE io)
    {
        rb_io_t *fptr = RFILE(io)->fptr;
        int fd;

        rb_io_check_closed(fptr);
        fd = fptr->fd;
        return INT2FIX(fd);
    }

Returns the integer file descriptor for the stream:

    $stdin.fileno             # => 0
    $stdout.fileno            # => 1
    $stderr.fileno            # => 2
    File.open('t.txt').fileno # => 10
    f.close

Also aliased as: to_i
flush → self
Source

    VALUE
    rb_io_flush(VALUE io)
    {
        return rb_io_flush_raw(io, 1);
    }

Flushes data buffered in `self` to the operating system (but does not necessarily flush data buffered in the operating system):

    $stdout.print 'no newline' # Not necessarily flushed.
    $stdout.flush              # Flushed.

fsync → 0
Source

    static VALUE
    rb_io_fsync(VALUE io)
    {
        rb_io_t *fptr;

        io = GetWriteIO(io);
        GetOpenFile(io, fptr);

        if (io_fflush(fptr) < 0)
            rb_sys_fail_on_write(fptr);

        if ((int)rb_io_blocking_region(fptr, nogvl_fsync, fptr))
            rb_sys_fail_path(fptr->pathv);

        return INT2FIX(0);
    }

Immediately writes to disk all data buffered in the stream, via the operating system’s `fsync(2)`.

Note this difference:

- `IO#sync=`: Ensures that data is flushed from the stream’s internal buffers, but does not guarantee that the operating system actually writes the data to disk.

- `IO#fsync`: Ensures both that data is flushed from internal buffers, and that data is written to disk.

Raises an exception if the operating system does not support `fsync(2)`.

getbyte → integer or nil
Source

    VALUE
    rb_io_getbyte(VALUE io)
    {
        rb_io_t *fptr;
        int c;

        GetOpenFile(io, fptr);
        rb_io_check_byte_readable(fptr);
        READ_CHECK(fptr);
        VALUE r_stdout = rb_ractor_stdout();
        if (fptr->fd == 0 && (fptr->mode & FMODE_TTY) && RB_TYPE_P(r_stdout, T_FILE)) {
            rb_io_t *ofp;
            GetOpenFile(r_stdout, ofp);
            if (ofp->mode & FMODE_TTY) {
                rb_io_flush(r_stdout);
            }
        }
        if (io_fillbuf(fptr) < 0) {
            return Qnil;
        }
        fptr->rbuf.off++;
        fptr->rbuf.len--;
        c = (unsigned char)fptr->rbuf.ptr[fptr->rbuf.off-1];
        return INT2FIX(c & 0xff);
    }

Reads and returns the next byte (in range 0..255) from the stream; returns `nil` if already at end-of-stream. See Byte IO.

    f = File.open('t.txt')
    f.getbyte # => 70
    f.close
    f = File.open('t.rus')
    f.getbyte # => 209
    f.close

Related: `IO#readbyte` (may raise `EOFError`).

getc → character or nil
Source

    static VALUE
    rb_io_getc(VALUE io)
    {
        rb_io_t *fptr;
        rb_encoding *enc;

        GetOpenFile(io, fptr);
        rb_io_check_char_readable(fptr);

        enc = io_input_encoding(fptr);
        READ_CHECK(fptr);
        return io_getc(fptr, enc);
    }

Reads and returns the next 1-character string from the stream; returns `nil` if already at end-of-stream. See Character IO.

    f = File.open('t.txt')
    f.getc     # => "F"
    f.close
    f = File.open('t.rus')
    f.getc.ord # => 1090
    f.close

Related: `IO#readchar` (may raise `EOFError`).

getch(min: nil, time: nil, intr: nil) → char
Source

    static VALUE
    console_getch(int argc, VALUE *argv, VALUE io)
    {
        rawmode_arg_t opts, *optp = rawmode_opt(&argc, argv, 0, 0, &opts);
    #ifndef _WIN32
        return ttymode(io, getc_call, io, set_rawmode, optp);
    #else
        rb_io_t *fptr;
        VALUE str;
        wint_t c;
        int len;
        char buf[8];
        wint_t wbuf[2];
    # ifndef HAVE_RB_IO_WAIT
        struct timeval *to = NULL, tv;
    # else
        VALUE timeout = Qnil;
    # endif

        GetOpenFile(io, fptr);
        if (optp) {
            if (optp->vtime) {
    # ifndef HAVE_RB_IO_WAIT
                to = &tv;
    # else
                struct timeval tv;
    # endif
                tv.tv_sec = optp->vtime / 10;
                tv.tv_usec = (optp->vtime % 10) * 100000;
    # ifdef HAVE_RB_IO_WAIT
                timeout = rb_fiber_scheduler_make_timeout(&tv);
    # endif
            }
            switch (optp->vmin) {
              case 1: /* default */
                break;
              case 0: /* return nil when timed out */
                if (optp->vtime) break;
                /* fallthru */
              default:
                rb_warning("min option larger than 1 ignored");
            }
            if (optp->intr) {
    # ifndef HAVE_RB_IO_WAIT
                int w = rb_wait_for_single_fd(fptr->fd, RB_WAITFD_IN, to);
                if (w < 0) rb_eof_error();
                if (!(w & RB_WAITFD_IN)) return Qnil;
    # else
                VALUE result = rb_io_wait(io, RB_INT2NUM(RUBY_IO_READABLE), timeout);
                if (!RTEST(result)) return Qnil;
    # endif
            }
            else if (optp->vtime) {
                rb_warning("Non-zero vtime option ignored if intr flag is unset");
            }
        }
        len = (int)(VALUE)rb_thread_call_without_gvl(nogvl_getch, wbuf, RUBY_UBF_IO, 0);
        switch (len) {
          case 0:
            return Qnil;
          case 2:
            buf[0] = (char)wbuf[0];
            c = wbuf[1];
            len = 1;
            do {
                buf[len++] = (unsigned char)c;
            } while ((c >>= CHAR_BIT) && len < (int)sizeof(buf));
            return rb_str_new(buf, len);
          default:
            c = wbuf[0];
            len = rb_uv_to_utf8(buf, c);
            str = rb_utf8_str_new(buf, len);
            return rb_str_conv_enc(str, NULL, rb_default_external_encoding());
        }
    #endif
    }

Reads and returns a character in raw mode.

See `IO#raw` for details on the parameters.

You must require ‘io/console’ to use this method.

getpass(prompt=nil) → string
Source

    static VALUE
    console_getpass(int argc, VALUE *argv, VALUE io)
    {
        VALUE str, wio;

        rb_check_arity(argc, 0, 1);
        wio = rb_io_get_write_io(io);
        if (wio == io && io == rb_stdin) wio = rb_stderr;
        prompt(argc, argv, wio);
        rb_io_flush(wio);
        str = rb_ensure(getpass_call, io, puts_call, wio);
        return str_chomp(str);
    }

Reads and returns a line without echo back. Prints `prompt` unless it is `nil`.

The newline character that terminates the read line is removed from the returned string, see `String#chomp!`.

You must require ‘io/console’ to use this method.

    require 'io/console'
    IO::console.getpass("Enter password:")
    Enter password:
    # => "mypassword"

gets(sep = $/, chomp: false) → string or nil
gets(limit, chomp: false) → string or nil
gets(sep, limit, chomp: false) → string or nil
Source

    static VALUE
    rb_io_gets_m(int argc, VALUE *argv, VALUE io)
    {
        VALUE str;

        str = rb_io_getline(argc, argv, io);
        rb_lastline_set(str);

        return str;
    }

Reads and returns a line from the stream; assigns the return value to `$_`. See Line IO.

With no arguments given, returns the next line as determined by line separator `$/`, or `nil` if none:

    f = File.open('t.txt')
    f.gets # => "First line\n"
    $_     # => "First line\n"
    f.gets # => "\n"
    f.gets # => "Fourth line\n"
    f.gets # => "Fifth line\n"
    f.gets # => nil
    f.close

With only string argument `sep` given, returns the next line as determined by line separator `sep`, or `nil` if none; see Line Separator:

    f = File.new('t.txt')
    f.gets('l')   # => "First l"
    f.gets('li')  # => "ine\nSecond li"
    f.gets('lin') # => "ne\n\nFourth lin"
    f.gets        # => "e\n"
    f.close

The two special values for `sep` are honored:

    f = File.new('t.txt')
    # Get all.
    f.gets(nil) # => "First line\nSecond line\n\nFourth line\nFifth line\n"
    f.rewind
    # Get paragraph (up to two line separators).
    f.gets('')  # => "First line\nSecond line\n\n"
    f.close

With only integer argument `limit` given, limits the number of bytes in the line; see Line Limit:

    # No more than one line.
    File.open('t.txt') {|f| f.gets(10) } # => "First line"
    File.open('t.txt') {|f| f.gets(11) } # => "First line\n"
    File.open('t.txt') {|f| f.gets(12) } # => "First line\n"

With arguments `sep` and `limit` given, combines the two behaviors (see Line Separator and Line Limit).

Optional keyword argument `chomp` specifies whether line separators are to be omitted:

    f = File.open('t.txt')
    # Chomp the lines.
    f.gets(chomp: true) # => "First line"
    f.gets(chomp: true) # => "Second line"
    f.gets(chomp: true) # => ""
    f.gets(chomp: true) # => "Fourth line"
    f.gets(chomp: true) # => "Fifth line"
    f.gets(chomp: true) # => nil
    f.close

goto(line, column) → io
Source

    static VALUE
    console_goto(VALUE io, VALUE y, VALUE x)
    {
    #ifdef _WIN32
        COORD pos;
        int fd = GetWriteFD(io);
        pos.X = NUM2UINT(x);
        pos.Y = NUM2UINT(y);
        if (!SetConsoleCursorPosition((HANDLE)rb_w32_get_osfhandle(fd), pos)) {
            rb_syserr_fail(LAST_ERROR, 0);
        }
    #else
        rb_io_write(io, rb_sprintf(CSI "%d;%dH", NUM2UINT(y)+1, NUM2UINT(x)+1));
    #endif
        return io;
    }

`Set` the cursor position at `line` and `column`.

You must require ‘io/console’ to use this method.

goto_column(column) → io
Source

    static VALUE
    console_goto_column(VALUE io, VALUE val)
    {
    #ifdef _WIN32
        HANDLE h;
        rb_console_size_t ws;
        COORD *pos = &ws.dwCursorPosition;

        h = (HANDLE)rb_w32_get_osfhandle(GetWriteFD(io));
        if (!GetConsoleScreenBufferInfo(h, &ws)) {
            rb_syserr_fail(LAST_ERROR, 0);
        }
        pos->X = NUM2INT(val);
        if (!SetConsoleCursorPosition(h, *pos)) {
            rb_syserr_fail(LAST_ERROR, 0);
        }
    #else
        rb_io_write(io, rb_sprintf(CSI "%dG", NUM2UINT(val)+1));
    #endif
        return io;
    }

`Set` the cursor position at `column` in the same line of the current position.

You must require ‘io/console’ to use this method.

iflush
Source

    static VALUE
    console_iflush(VALUE io)
    {
    #if defined HAVE_TERMIOS_H || defined HAVE_TERMIO_H
        int fd = GetReadFD(io);
        if (tcflush(fd, TCIFLUSH)) sys_fail(io);
    #endif

        return io;
    }

Flushes input buffer in kernel.

You must require ‘io/console’ to use this method.

inspect → string
Source

    static VALUE
    rb_io_inspect(VALUE obj)
    {
        rb_io_t *fptr;
        VALUE result;
        static const char closed[] = " (closed)";

        fptr = RFILE(obj)->fptr;
        if (!fptr) return rb_any_to_s(obj);
        result = rb_str_new_cstr("#<");
        rb_str_append(result, rb_class_name(CLASS_OF(obj)));
        rb_str_cat2(result, ":");
        if (NIL_P(fptr->pathv)) {
            if (fptr->fd < 0) {
                rb_str_cat(result, closed+1, strlen(closed)-1);
            }
            else {
                rb_str_catf(result, "fd %d", fptr->fd);
            }
        }
        else {
            rb_str_append(result, fptr->pathv);
            if (fptr->fd < 0) {
                rb_str_cat(result, closed, strlen(closed));
            }
        }
        return rb_str_cat2(result, ">");
    }

Returns a string representation of `self`:

    f = File.open('t.txt')
    f.inspect # => "#<File:t.txt>"
    f.close

internal_encoding → encoding or nil
Source

    static VALUE
    rb_io_internal_encoding(VALUE io)
    {
        rb_io_t *fptr = RFILE(rb_io_taint_check(io))->fptr;

        if (!fptr->encs.enc2) return Qnil;
        return rb_enc_from_encoding(io_read_encoding(fptr));
    }

Returns the `Encoding` object that represents the encoding of the internal string, if conversion is specified, or `nil` otherwise.

See Encodings.

ioctl(integer_cmd, argument) → integer
Source

    static VALUE
    rb_io_ioctl(int argc, VALUE *argv, VALUE io)
    {
        VALUE req, arg;

        rb_scan_args(argc, argv, "11", &req, &arg);
        return rb_ioctl(io, req, arg);
    }

Invokes Posix system call ioctl(2), which issues a low-level command to an I/O device.

Issues a low-level command to an I/O device. The arguments and returned value are platform-dependent. The effect of the call is platform-dependent.

If argument `argument` is an integer, it is passed directly; if it is a string, it is interpreted as a binary sequence of bytes.

Not implemented on all platforms.

ioflush
Source

    static VALUE
    console_ioflush(VALUE io)
    {
    #if defined HAVE_TERMIOS_H || defined HAVE_TERMIO_H
        int fd1 = GetReadFD(io);
        int fd2 = GetWriteFD(io);

        if (fd2 != -1 && fd1 != fd2) {
            if (tcflush(fd1, TCIFLUSH)) sys_fail(io);
            if (tcflush(fd2, TCOFLUSH)) sys_fail(io);
        }
        else {
            if (tcflush(fd1, TCIOFLUSH)) sys_fail(io);
        }
    #endif

        return io;
    }

Flushes input and output buffers in kernel.

You must require ‘io/console’ to use this method.

isatty → true or false
Source

    static VALUE
    rb_io_isatty(VALUE io)
    {
        rb_io_t *fptr;

        GetOpenFile(io, fptr);
        return RBOOL(isatty(fptr->fd) != 0);
    }

Returns `true` if the stream is associated with a terminal device (tty), `false` otherwise:

    f = File.new('t.txt').isatty    #=> false
    f.close
    f = File.new('/dev/tty').isatty #=> true
    f.close

Also aliased as: tty?
lineno → integer
Source

    static VALUE
    rb_io_lineno(VALUE io)
    {
        rb_io_t *fptr;

        GetOpenFile(io, fptr);
        rb_io_check_char_readable(fptr);
        return INT2NUM(fptr->lineno);
    }

Returns the current line number for the stream; see Line Number.

lineno = integer → integer
Source

    static VALUE
    rb_io_set_lineno(VALUE io, VALUE lineno)
    {
        rb_io_t *fptr;

        GetOpenFile(io, fptr);
        rb_io_check_char_readable(fptr);
        fptr->lineno = NUM2INT(lineno);
        return lineno;
    }

Sets and returns the line number for the stream; see Line Number.

noecho {|io| }
Source

    static VALUE
    console_noecho(VALUE io)
    {
        return ttymode(io, rb_yield, io, set_noecho, NULL);
    }

Yields `self` with disabling echo back.

    STDIN.noecho(&:gets)

will read and return a line without echo back.

You must require ‘io/console’ to use this method.

nonblock {|io| } → object
nonblock(boolean) {|io| } → object
Source

    static VALUE
    rb_io_nonblock_block(int argc, VALUE *argv, VALUE self)
    {
        int nb = 1;

        int descriptor = rb_io_descriptor(self);

        if (argc > 0) {
            VALUE v;
            rb_scan_args(argc, argv, "01", &v);
            nb = RTEST(v);
        }

        int current_flags = get_fcntl_flags(descriptor);
        int restore[2] = {descriptor, current_flags};

        if (!io_nonblock_set(descriptor, current_flags, nb))
            return rb_yield(self);

        return rb_ensure(rb_yield, self, io_nonblock_restore, (VALUE)restore);
    }

Yields `self` in non-blocking mode.

When `false` is given as an argument, `self` is yielded in blocking mode. The original mode is restored after the block is executed.

nonblock = boolean → boolean
Source

    static VALUE
    rb_io_nonblock_set(VALUE self, VALUE value)
    {
        if (RTEST(value)) {
            rb_io_t *fptr;
            GetOpenFile(self, fptr);
            rb_io_set_nonblock(fptr);
        }
        else {
            int descriptor = rb_io_descriptor(self);
            io_nonblock_set(descriptor, get_fcntl_flags(descriptor), RTEST(value));
        }

        return self;
    }

Enables non-blocking mode on a stream when set to `true`, and blocking mode when set to `false`.

This method set or clear O_NONBLOCK flag for the file descriptor in ios.

The behavior of most `IO` methods is not affected by this flag because they retry system calls to complete their task after EAGAIN and partial read/write. (An exception is `IO#syswrite` which doesn’t retry.)

This method can be used to clear non-blocking mode of standard I/O. Since nonblocking methods (`read_nonblock`, etc.) set non-blocking mode but they doesn’t clear it, this method is usable as follows.

    END { STDOUT.nonblock = false }
    STDOUT.write_nonblock("foo")

Since the flag is shared across processes and many non-Ruby commands doesn’t expect standard I/O with non-blocking mode, it would be safe to clear the flag before Ruby program exits.

For example following Ruby program leaves STDIN/STDOUT/STDER non-blocking mode. (STDIN, STDOUT and STDERR are connected to a terminal. So making one of them nonblocking-mode effects other two.) Thus cat command try to read from standard input and it causes “Resource temporarily unavailable” error (EAGAIN).

    % ruby -e '
    STDOUT.write_nonblock("foo\n")'; cat
    foo
    cat: -: Resource temporarily unavailable

Clearing the flag makes the behavior of cat command normal. (cat command waits input from standard input.)

    % ruby -rio/nonblock -e '
    END { STDOUT.nonblock = false }
    STDOUT.write_nonblock("foo")
    '; cat
    foo

nonblock? → boolean
Source

    static VALUE
    rb_io_nonblock_p(VALUE io)
    {
        if (get_fcntl_flags(rb_io_descriptor(io)) & O_NONBLOCK)
            return Qtrue;
        return Qfalse;
    }

Returns `true` if an `IO` object is in non-blocking mode.

nread → int
Source

    static VALUE
    io_nread(VALUE io)
    {
        rb_io_t *fptr;
        int len;
        ioctl_arg n;

        GetOpenFile(io, fptr);
        rb_io_check_readable(fptr);
        len = rb_io_read_pending(fptr);
        if (len > 0) return INT2FIX(len);

    #ifdef HAVE_RB_IO_DESCRIPTOR
        int fd = rb_io_descriptor(io);
    #else
        int fd = fptr->fd;
    #endif

        if (!FIONREAD_POSSIBLE_P(fd)) return INT2FIX(0);
        if (ioctl(fd, FIONREAD, &n)) return INT2FIX(0);
        if (n > 0) return ioctl_arg2num(n);
        return INT2FIX(0);
    }

Returns number of bytes that can be read without blocking. Returns zero if no information available.

You must require ‘io/wait’ to use this method.

oflush
Source

    static VALUE
    console_oflush(VALUE io)
    {
        int fd = GetWriteFD(io);
    #if defined HAVE_TERMIOS_H || defined HAVE_TERMIO_H
        if (tcflush(fd, TCOFLUSH)) sys_fail(io);
    #endif
        (void)fd;
        return io;
    }

Flushes output buffer in kernel.

You must require ‘io/console’ to use this method.

path → string or nil
Source

    VALUE
    rb_io_path(VALUE io)
    {
        rb_io_t *fptr = RFILE(io)->fptr;

        if (!fptr)
            return Qnil;

        return rb_obj_dup(fptr->pathv);
    }

Returns the path associated with the `IO`, or `nil` if there is no path associated with the `IO`. It is not guaranteed that the path exists on the filesystem.

    $stdin.path # => "<STDIN>"

    File.open("testfile") {|f| f.path} # => "testfile"

Also aliased as: to_path
pathconf(name) → Integer
Source

    static VALUE
    io_pathconf(VALUE io, VALUE arg)
    {
        int name;
        long ret;

        name = NUM2INT(arg);

        errno = 0;
        ret = fpathconf(rb_io_descriptor(io), name);
        if (ret == -1) {
            if (errno == 0) /* no limit */
                return Qnil;
            rb_sys_fail("fpathconf");
        }
        return LONG2NUM(ret);
    }

Returns pathname configuration variable using fpathconf().

name should be a constant under `Etc` which begins with `PC_`.

The return value is an integer or nil. nil means indefinite limit. (fpathconf() returns -1 but errno is not set.)

    require 'etc'
    IO.pipe {|r, w|
      p w.pathconf(Etc::PC_PIPE_BUF) #=> 4096
    }

pid → integer or nil
Source

    static VALUE
    rb_io_pid(VALUE io)
    {
        rb_io_t *fptr;

        GetOpenFile(io, fptr);
        if (!fptr->pid)
            return Qnil;
        return PIDT2NUM(fptr->pid);
    }

Returns the process ID of a child process associated with the stream, which will have been set by IO#popen, or `nil` if the stream was not created by IO#popen:

    pipe = IO.popen("-")
    if pipe
      $stderr.puts "In parent, child pid is #{pipe.pid}"
    else
      $stderr.puts "In child, pid is #{$$}"
    end

Output:

    In child, pid is 26209
    In parent, child pid is 26209

pos
Alias for: tell
pos = new_position → new_position
Source

    static VALUE
    rb_io_set_pos(VALUE io, VALUE offset)
    {
        rb_io_t *fptr;
        rb_off_t pos;

        pos = NUM2OFFT(offset);
        GetOpenFile(io, fptr);
        pos = io_seek(fptr, pos, SEEK_SET);
        if (pos < 0 && errno) rb_sys_fail_path(fptr->pathv);

        return OFFT2NUM(pos);
    }

Seeks to the given `new_position` (in bytes); see Position:

    f = File.open('t.txt')
    f.tell     # => 0
    f.pos = 20 # => 20
    f.tell     # => 20
    f.close

Related: `IO#seek`, `IO#tell`.

pread(maxlen, offset) → string
pread(maxlen, offset, out_string) → string
Source

    static VALUE
    rb_io_pread(int argc, VALUE *argv, VALUE io)
    {
        VALUE len, offset, str;
        rb_io_t *fptr;
        ssize_t n;
        struct prdwr_internal_arg arg;
        int shrinkable;

        rb_scan_args(argc, argv, "21", &len, &offset, &str);
        arg.count = NUM2SIZET(len);
        arg.offset = NUM2OFFT(offset);

        shrinkable = io_setstrbuf(&str, (long)arg.count);
        if (arg.count == 0) return str;
        arg.buf = RSTRING_PTR(str);

        GetOpenFile(io, fptr);
        rb_io_check_byte_readable(fptr);

        arg.io = fptr;
        arg.fd = fptr->fd;
        rb_io_check_closed(fptr);

        rb_str_locktmp(str);
        n = (ssize_t)rb_ensure(pread_internal_call, (VALUE)&arg, rb_str_unlocktmp, str);

        if (n < 0) {
            rb_sys_fail_path(fptr->pathv);
        }
        io_set_read_length(str, n, shrinkable);
        if (n == 0 && arg.count > 0) {
            rb_eof_error();
        }

        return str;
    }

Behaves like `IO#readpartial`, except that it:

- Reads at the given `offset` (in bytes).

- Disregards, and does not modify, the stream’s position (see Position).

- Bypasses any user space buffering in the stream.

Because this method does not disturb the stream’s state (its position, in particular), `pread` allows multiple threads and processes to use the same IO object for reading at various offsets.

    f = File.open('t.txt')
    f.read # => "First line\nSecond line\n\nFourth line\nFifth line\n"
    f.pos  # => 52
    # Read 12 bytes at offset 0.
    f.pread(12, 0) # => "First line\n"
    # Read 9 bytes at offset 8.
    f.pread(9, 8)  # => "ne\nSecon"
    f.close

Not available on some platforms.

pressed?(key) → bool
Source

    static VALUE
    console_key_pressed_p(VALUE io, VALUE k)
    {
        int vk = -1;

        if (FIXNUM_P(k)) {
            vk = NUM2UINT(k);
        }
        else {
            const struct vktable *t;
            const char *kn;
            if (SYMBOL_P(k)) {
                k = rb_sym2str(k);
                kn = RSTRING_PTR(k);
            }
            else {
                kn = StringValuePtr(k);
            }
            t = console_win32_vk(kn, RSTRING_LEN(k));
            if (!t || (vk = (short)t->vk) == -1) {
                rb_raise(rb_eArgError, "unknown virtual key code: % "PRIsVALUE, k);
            }
        }
        return GetKeyState(vk) & 0x80 ? Qtrue : Qfalse;
    }

Returns `true` if `key` is pressed. `key` may be a virtual key code or its name (`String` or `Symbol`) with out “VK_” prefix.

This method is Windows only.

You must require ‘io/console’ to use this method.

print(*objects) → nil
Source

    VALUE
    rb_io_print(int argc, const VALUE *argv, VALUE out)
    {
        int i;
        VALUE line;

        /* if no argument given, print `$_' */
        if (argc == 0) {
            argc = 1;
            line = rb_lastline_get();
            argv = &line;
        }
        if (argc > 1 && !NIL_P(rb_output_fs)) {
            rb_category_warn(RB_WARN_CATEGORY_DEPRECATED, "$, is set to non-nil value");
        }
        for (i=0; i<argc; i++) {
            if (!NIL_P(rb_output_fs) && i>0) {
                rb_io_write(out, rb_output_fs);
            }
            rb_io_write(out, argv[i]);
        }
        if (argc > 0 && !NIL_P(rb_output_rs)) {
            rb_io_write(out, rb_output_rs);
        }

        return Qnil;
    }

Writes the given objects to the stream; returns `nil`. Appends the output record separator `$OUTPUT_RECORD_SEPARATOR` (`$\`), if it is not `nil`. See Line IO.

With argument `objects` given, for each object:

- Converts via its method `to_s` if not a string.

- Writes to the stream.

- If not the last object, writes the output field separator `$OUTPUT_FIELD_SEPARATOR` (`$,`) if it is not `nil`.

With default separators:

    f = File.open('t.tmp', 'w+')
    objects = [0, 0.0, Rational(0, 1), Complex(0, 0), :zero, 'zero']
    p $OUTPUT_RECORD_SEPARATOR
    p $OUTPUT_FIELD_SEPARATOR
    f.print(*objects)
    f.rewind
    p f.read
    f.close

Output:

    nil
    nil
    "00.00/10+0izerozero"

With specified separators:

    $\ = "\n"
    $, = ','
    f.rewind
    f.print(*objects)
    f.rewind
    p f.read

Output:

    "0,0.0,0/1,0+0i,zero,zero\n"

With no argument given, writes the content of `$_` (which is usually the most recent user input):

    f = File.open('t.tmp', 'w+')
    gets # Sets $_ to the most recent user input.
    f.print
    f.close

printf(format_string, *objects) → nil
Source

    VALUE
    rb_io_printf(int argc, const VALUE *argv, VALUE out)
    {
        rb_io_write(out, rb_f_sprintf(argc, argv));
        return Qnil;
    }

Formats and writes `objects` to the stream.

For details on `format_string`, see Format Specifications.

putc(object) → object
Source

    static VALUE
    rb_io_putc(VALUE io, VALUE ch)
    {
        VALUE str;
        if (RB_TYPE_P(ch, T_STRING)) {
            str = rb_str_substr(ch, 0, 1);
        }
        else {
            char c = NUM2CHR(ch);
            str = rb_str_new(&c, 1);
        }
        rb_io_write(io, str);
        return ch;
    }

Writes a character to the stream. See Character IO.

If `object` is numeric, converts to integer if necessary, then writes the character whose code is the least significant byte; if `object` is a string, writes the first character:

    $stdout.putc "A"
    $stdout.putc 65

Output:

    AA

puts(*objects) → nil
Source

    VALUE
    rb_io_puts(int argc, const VALUE *argv, VALUE out)
    {
        VALUE line, args[2];

        /* if no argument given, print newline. */
        if (argc == 0) {
            rb_io_write(out, rb_default_rs);
            return Qnil;
        }
        for (int i = 0; i < argc; i++) {
            // Convert the argument to a string:
            if (RB_TYPE_P(argv[i], T_STRING)) {
                line = argv[i];
            }
            else if (rb_exec_recursive(io_puts_ary, argv[i], out)) {
                continue;
            }
            else {
                line = rb_obj_as_string(argv[i]);
            }

            // Write the line:
            int n = 0;
            if (RSTRING_LEN(line) == 0) {
                args[n++] = rb_default_rs;
            }
            else {
                args[n++] = line;
                if (!rb_str_end_with_asciichar(line, '\n')) {
                    args[n++] = rb_default_rs;
                }
            }

            rb_io_writev(out, n, args);
        }

        return Qnil;
    }

Writes the given `objects` to the stream, which must be open for writing; returns `nil`.\ Writes a newline after each that does not already end with a newline sequence. If called without arguments, writes a newline. See Line IO.

Note that each added newline is the character `"\n"<//tt>, not the output record separator (<tt>$\`).

Treatment for each object:

- String: writes the string.

- Neither string nor array: writes `object.to_s`.

- Array: writes each element of the array; arrays may be nested.

To keep these examples brief, we define this helper method:

    def show(*objects)
      # Puts objects to file.
      f = File.new('t.tmp', 'w+')
      f.puts(objects)
      # Return file content.
      f.rewind
      p f.read
      f.close
    end

    # Strings without newlines.
    show('foo', 'bar', 'baz')     # => "foo\nbar\nbaz\n"
    # Strings, some with newlines.
    show("foo\n", 'bar', "baz\n") # => "foo\nbar\nbaz\n"

    # Neither strings nor arrays:
    show(0, 0.0, Rational(0, 1), Complex(9, 0), :zero)
    # => "0\n0.0\n0/1\n9+0i\nzero\n"

    # Array of strings.
    show(['foo', "bar\n", 'baz']) # => "foo\nbar\nbaz\n"
    # Nested arrays.
    show([[[0, 1], 2, 3], 4, 5])  # => "0\n1\n2\n3\n4\n5\n"

pwrite(object, offset) → integer
Source

    static VALUE
    rb_io_pwrite(VALUE io, VALUE str, VALUE offset)
    {
        rb_io_t *fptr;
        ssize_t n;
        struct prdwr_internal_arg arg;
        VALUE tmp;

        if (!RB_TYPE_P(str, T_STRING))
            str = rb_obj_as_string(str);

        arg.offset = NUM2OFFT(offset);

        io = GetWriteIO(io);
        GetOpenFile(io, fptr);
        rb_io_check_writable(fptr);

        arg.io = fptr;
        arg.fd = fptr->fd;

        tmp = rb_str_tmp_frozen_acquire(str);
        arg.buf = RSTRING_PTR(tmp);
        arg.count = (size_t)RSTRING_LEN(tmp);

        n = (ssize_t)rb_io_blocking_region_wait(fptr, internal_pwrite_func, &arg, RUBY_IO_WRITABLE);
        if (n < 0) rb_sys_fail_path(fptr->pathv);
        rb_str_tmp_frozen_release(str, tmp);

        return SSIZET2NUM(n);
    }

Behaves like `IO#write`, except that it:

- Writes at the given `offset` (in bytes).

- Disregards, and does not modify, the stream’s position (see Position).

- Bypasses any user space buffering in the stream.

Because this method does not disturb the stream’s state (its position, in particular), `pwrite` allows multiple threads and processes to use the same IO object for writing at various offsets.

    f = File.open('t.tmp', 'w+')
    # Write 6 bytes at offset 3.
    f.pwrite('ABCDEF', 3) # => 6
    f.rewind
    f.read # => "\u0000\u0000\u0000ABCDEF"
    f.close

Not available on some platforms.

raw(min: nil, time: nil, intr: nil) {|io| }
Source

    static VALUE
    console_raw(int argc, VALUE *argv, VALUE io)
    {
        rawmode_arg_t opts, *optp = rawmode_opt(&argc, argv, 0, 0, &opts);
        return ttymode(io, rb_yield, io, set_rawmode, optp);
    }

Yields `self` within raw mode, and returns the result of the block.

    STDIN.raw(&:gets)

will read and return a line without echo back and line editing.

The parameter `min` specifies the minimum number of bytes that should be received when a read operation is performed. (default: 1)

The parameter `time` specifies the timeout in seconds with a precision of 1/10 of a second. (default: 0)

If the parameter `intr` is `true`, enables break, interrupt, quit, and suspend special characters.

Refer to the manual page of termios for further details.

You must require ‘io/console’ to use this method.

raw!(min: nil, time: nil, intr: nil) → io
Source

    static VALUE
    console_set_raw(int argc, VALUE *argv, VALUE io)
    {
        conmode t;
        rawmode_arg_t opts, *optp = rawmode_opt(&argc, argv, 0, 0, &opts);
        int fd = GetReadFD(io);
        if (!getattr(fd, &t)) sys_fail(io);
        set_rawmode(&t, optp);
        if (!setattr(fd, &t)) sys_fail(io);
        return io;
    }

Enables raw mode, and returns `io`.

If the terminal mode needs to be back, use `io.raw { ... }`.

See `IO#raw` for details on the parameters.

You must require ‘io/console’ to use this method.

read(maxlen = nil, out_string = nil) → new_string, out_string, or nil
Source

    static VALUE
    io_read(int argc, VALUE *argv, VALUE io)
    {
        rb_io_t *fptr;
        long n, len;
        VALUE length, str;
        int shrinkable;
    #if RUBY_CRLF_ENVIRONMENT
        int previous_mode;
    #endif

        rb_scan_args(argc, argv, "02", &length, &str);

        if (NIL_P(length)) {
            GetOpenFile(io, fptr);
            rb_io_check_char_readable(fptr);
            return read_all(fptr, remain_size(fptr), str);
        }
        len = NUM2LONG(length);
        if (len < 0) {
            rb_raise(rb_eArgError, "negative length %ld given", len);
        }

        shrinkable = io_setstrbuf(&str,len);

        GetOpenFile(io, fptr);
        rb_io_check_byte_readable(fptr);
        if (len == 0) {
            io_set_read_length(str, 0, shrinkable);
            return str;
        }

        READ_CHECK(fptr);
    #if RUBY_CRLF_ENVIRONMENT
        previous_mode = set_binary_mode_with_seek_cur(fptr);
    #endif
        n = io_fread(str, 0, len, fptr);
        io_set_read_length(str, n, shrinkable);
    #if RUBY_CRLF_ENVIRONMENT
        if (previous_mode == O_TEXT) {
            setmode(fptr->fd, O_TEXT);
        }
    #endif
        if (n == 0) return Qnil;

        return str;
    }

Reads bytes from the stream; the stream must be opened for reading (see Access Modes):

- If `maxlen` is `nil`, reads all bytes using the stream’s data mode.

- Otherwise reads up to `maxlen` bytes in binary mode.

Returns a string (either a new string or the given `out_string`) containing the bytes read. The encoding of the string depends on both `maxLen` and `out_string`:

- `maxlen` is `nil`: uses internal encoding of `self` (regardless of whether `out_string` was given).

- `maxlen` not `nil`:

  - `out_string` given: encoding of `out_string` not modified.

  - `out_string` not given: ASCII-8BIT is used.

Without Argument `out_string`

When argument `out_string` is omitted, the returned value is a new string:

    f = File.new('t.txt')
    f.read
    # => "First line\nSecond line\n\nFourth line\nFifth line\n"
    f.rewind
    f.read(30) # => "First line\r\nSecond line\r\n\r\nFou"
    f.read(30) # => "rth line\r\nFifth line\r\n"
    f.read(30) # => nil
    f.close

If `maxlen` is zero, returns an empty string.

With Argument `out_string`

When argument `out_string` is given, the returned value is `out_string`, whose content is replaced:

    f = File.new('t.txt')
    s = 'foo'      # => "foo"
    f.read(nil, s) # => "First line\nSecond line\n\nFourth line\nFifth line\n"
    s              # => "First line\nSecond line\n\nFourth line\nFifth line\n"
    f.rewind
    s = 'bar'
    f.read(30, s)  # => "First line\r\nSecond line\r\n\r\nFou"
    s              # => "First line\r\nSecond line\r\n\r\nFou"
    s = 'baz'
    f.read(30, s)  # => "rth line\r\nFifth line\r\n"
    s              # => "rth line\r\nFifth line\r\n"
    s = 'bat'
    f.read(30, s)  # => nil
    s              # => ""
    f.close

Note that this method behaves like the fread() function in C. This means it retries to invoke read(2) system calls to read data with the specified maxlen (or until EOF).

This behavior is preserved even if the stream is in non-blocking mode. (This method is non-blocking-flag insensitive as other methods.)

If you need the behavior like a single read(2) system call, consider `readpartial`, `read_nonblock`, and `sysread`.

Related: `IO#write`.

read_nonblock(maxlen [, options]) → string
read_nonblock(maxlen, outbuf [, options]) → outbuf
Source

    # File io.rb, line 62
    def read_nonblock(len, buf = nil, exception: true)
      Primitive.io_read_nonblock(len, buf, exception)
    end

Reads at most maxlen bytes from ios using the read(2) system call after O_NONBLOCK is set for the underlying file descriptor.

If the optional outbuf argument is present, it must reference a `String`, which will receive the data. The outbuf will contain only the received data after the method call even if it is not empty at the beginning.

`read_nonblock` just calls the read(2) system call. It causes all errors the read(2) system call causes: Errno::EWOULDBLOCK, Errno::EINTR, etc. The caller should care such errors.

If the exception is Errno::EWOULDBLOCK or Errno::EAGAIN, it is extended by `IO::WaitReadable`. So `IO::WaitReadable` can be used to rescue the exceptions for retrying read_nonblock.

`read_nonblock` causes `EOFError` on EOF.

On some platforms, such as Windows, non-blocking mode is not supported on `IO` objects other than sockets. In such cases, Errno::EBADF will be raised.

If the read byte buffer is not empty, `read_nonblock` reads from the buffer like readpartial. In this case, the read(2) system call is not called.

When `read_nonblock` raises an exception kind of `IO::WaitReadable`, `read_nonblock` should not be called until io is readable for avoiding busy loop. This can be done as follows.

    # emulates blocking read (readpartial).
    begin
      result = io.read_nonblock(maxlen)
    rescue IO::WaitReadable
      IO.select([io])
      retry
    end

Although `IO#read_nonblock` doesn’t raise `IO::WaitWritable`. `OpenSSL::Buffering#read_nonblock` can raise `IO::WaitWritable`. If `IO` and SSL should be used polymorphically, `IO::WaitWritable` should be rescued too. See the document of `OpenSSL::Buffering#read_nonblock` for sample code.

Note that this method is identical to readpartial except the non-blocking flag is set.

By specifying a keyword argument exception to `false`, you can indicate that `read_nonblock` should not raise an `IO::WaitReadable` exception, but return the symbol `:wait_readable` instead. At EOF, it will return nil instead of raising `EOFError`.

readbyte → integer
Source

    static VALUE
    rb_io_readbyte(VALUE io)
    {
        VALUE c = rb_io_getbyte(io);

        if (NIL_P(c)) {
            rb_eof_error();
        }
        return c;
    }

Reads and returns the next byte (in range 0..255) from the stream; raises `EOFError` if already at end-of-stream. See Byte IO.

    f = File.open('t.txt')
    f.readbyte # => 70
    f.close
    f = File.open('t.rus')
    f.readbyte # => 209
    f.close

Related: `IO#getbyte` (will not raise `EOFError`).

readchar → string
Source

    static VALUE
    rb_io_readchar(VALUE io)
    {
        VALUE c = rb_io_getc(io);

        if (NIL_P(c)) {
            rb_eof_error();
        }
        return c;
    }

Reads and returns the next 1-character string from the stream; raises `EOFError` if already at end-of-stream. See Character IO.

    f = File.open('t.txt')
    f.readchar     # => "F"
    f.close
    f = File.open('t.rus')
    f.readchar.ord # => 1090
    f.close

Related: `IO#getc` (will not raise `EOFError`).

readline(sep = $/, chomp: false) → string
readline(limit, chomp: false) → string
readline(sep, limit, chomp: false) → string
Source

    # File io.rb, line 133
    def readline(sep = $/, limit = nil, chomp: false)
      Primitive.io_readline(sep, limit, chomp)
    end

Reads a line as with `IO#gets`, but raises `EOFError` if already at end-of-stream.

Optional keyword argument `chomp` specifies whether line separators are to be omitted.

readlines(sep = $/, chomp: false) → array
readlines(limit, chomp: false) → array
readlines(sep, limit, chomp: false) → array
Source

    static VALUE
    rb_io_readlines(int argc, VALUE *argv, VALUE io)
    {
        struct getline_arg args;

        prepare_getline_args(argc, argv, &args, io);
        return io_readlines(&args, io);
    }

Reads and returns all remaining line from the stream; does not modify `$_`. See Line IO.

With no arguments given, returns lines as determined by line separator `$/`, or `nil` if none:

    f = File.new('t.txt')
    f.readlines
    # => ["First line\n", "Second line\n", "\n", "Fourth line\n", "Fifth line\n"]
    f.readlines # => []
    f.close

With only string argument `sep` given, returns lines as determined by line separator `sep`, or `nil` if none; see Line Separator:

    f = File.new('t.txt')
    f.readlines('li')
    # => ["First li", "ne\nSecond li", "ne\n\nFourth li", "ne\nFifth li", "ne\n"]
    f.close

The two special values for `sep` are honored:

    f = File.new('t.txt')
    # Get all into one string.
    f.readlines(nil)
    # => ["First line\nSecond line\n\nFourth line\nFifth line\n"]
    # Get paragraphs (up to two line separators).
    f.rewind
    f.readlines('')
    # => ["First line\nSecond line\n\n", "Fourth line\nFifth line\n"]
    f.close

With only integer argument `limit` given, limits the number of bytes in each line; see Line Limit:

    f = File.new('t.txt')
    f.readlines(8)
    # => ["First li", "ne\n", "Second l", "ine\n", "\n", "Fourth l", "ine\n", "Fifth li", "ne\n"]
    f.close

With arguments `sep` and `limit` given, combines the two behaviors (see Line Separator and Line Limit).

Optional keyword argument `chomp` specifies whether line separators are to be omitted:

    f = File.new('t.txt')
    f.readlines(chomp: true)
    # => ["First line", "Second line", "", "Fourth line", "Fifth line"]
    f.close

readpartial(maxlen) → string
readpartial(maxlen, out_string) → out_string
Source

    static VALUE
    io_readpartial(int argc, VALUE *argv, VALUE io)
    {
        VALUE ret;

        ret = io_getpartial(argc, argv, io, Qnil, 0);
        if (NIL_P(ret))
            rb_eof_error();
        return ret;
    }

Reads up to `maxlen` bytes from the stream; returns a string (either a new string or the given `out_string`). Its encoding is:

- The unchanged encoding of `out_string`, if `out_string` is given.

- ASCII-8BIT, otherwise.

- Contains `maxlen` bytes from the stream, if available.

- Otherwise contains all available bytes, if any available.

- Otherwise is an empty string.

With the single non-negative integer argument `maxlen` given, returns a new string:

    f = File.new('t.txt')
    f.readpartial(20) # => "First line\nSecond l"
    f.readpartial(20) # => "ine\n\nFourth line\n"
    f.readpartial(20) # => "Fifth line\n"
    f.readpartial(20) # Raises EOFError.
    f.close

With both argument `maxlen` and string argument `out_string` given, returns modified `out_string`:

    f = File.new('t.txt')
    s = 'foo'
    f.readpartial(20, s) # => "First line\nSecond l"
    s = 'bar'
    f.readpartial(0, s)  # => ""
    f.close

This method is useful for a stream such as a pipe, a socket, or a tty. It blocks only when no data is immediately available. This means that it blocks only when all of the following are true:

- The byte buffer in the stream is empty.

- The content of the stream is empty.

- The stream is not at EOF.

When blocked, the method waits for either more data or EOF on the stream:

- If more data is read, the method returns the data.

- If EOF is reached, the method raises `EOFError`.

When not blocked, the method responds immediately:

- Returns data from the buffer if there is any.

- Otherwise returns data from the stream if there is any.

- Otherwise raises `EOFError` if the stream has reached EOF.

Note that this method is similar to sysread. The differences are:

- If the byte buffer is not empty, read from the byte buffer instead of “sysread for buffered `IO` (`IOError`)”.

- It doesn’t cause Errno::EWOULDBLOCK and Errno::EINTR. When readpartial meets EWOULDBLOCK and EINTR by read system call, readpartial retries the system call.

The latter means that readpartial is non-blocking-flag insensitive. It blocks on the situation `IO#sysread` causes Errno::EWOULDBLOCK as if the fd is blocking mode.

Examples:

    #                        # Returned      Buffer Content    Pipe Content
    r, w = IO.pipe           #
    w << 'abc'               #               ""                "abc".
    r.readpartial(4096)      # => "abc"      ""                ""
    r.readpartial(4096)      # (Blocks because buffer and pipe are empty.)

    #                        # Returned      Buffer Content    Pipe Content
    r, w = IO.pipe           #
    w << 'abc'               #               ""                "abc"
    w.close                  #               ""                "abc" EOF
    r.readpartial(4096)      # => "abc"      ""                 EOF
    r.readpartial(4096)      # raises EOFError

    #                        # Returned      Buffer Content    Pipe Content
    r, w = IO.pipe           #
    w << "abc\ndef\n"        #               ""                "abc\ndef\n"
    r.gets                   # => "abc\n"    "def\n"           ""
    w << "ghi\n"             #               "def\n"           "ghi\n"
    r.readpartial(4096)      # => "def\n"    ""                "ghi\n"
    r.readpartial(4096)      # => "ghi\n"    ""                ""

ready? → truthy or falsy
Source

    static VALUE
    io_ready_p(VALUE io)
    {
        rb_io_t *fptr;
    #ifndef HAVE_RB_IO_WAIT
        struct timeval tv = {0, 0};
    #endif

        GetOpenFile(io, fptr);
        rb_io_check_readable(fptr);
        if (rb_io_read_pending(fptr)) return Qtrue;

    #ifndef HAVE_RB_IO_WAIT
        return wait_for_single_fd(fptr, RB_WAITFD_IN, &tv) ? Qtrue : Qfalse;
    #else
        return io_wait_event(io, RUBY_IO_READABLE, RB_INT2NUM(0), 1);
    #endif
    }

Returns a truthy value if input available without blocking, or a falsy value.

You must require ‘io/wait’ to use this method.

reopen(other_io) → self
reopen(path, mode = 'r', **opts) → self
Source

    static VALUE
    rb_io_reopen(int argc, VALUE *argv, VALUE file)
    {
        VALUE fname, nmode, opt;
        int oflags;
        rb_io_t *fptr;

        if (rb_scan_args(argc, argv, "11:", &fname, &nmode, &opt) == 1) {
            VALUE tmp = rb_io_check_io(fname);
            if (!NIL_P(tmp)) {
                return io_reopen(file, tmp);
            }
        }

        FilePathValue(fname);
        rb_io_taint_check(file);
        fptr = RFILE(file)->fptr;
        if (!fptr) {
            fptr = RFILE(file)->fptr = ZALLOC(rb_io_t);
        }

        if (!NIL_P(nmode) || !NIL_P(opt)) {
            int fmode;
            struct rb_io_encoding convconfig;

            rb_io_extract_modeenc(&nmode, 0, opt, &oflags, &fmode, &convconfig);
            if (RUBY_IO_EXTERNAL_P(fptr) &&
                ((fptr->mode & FMODE_READWRITE) & (fmode & FMODE_READWRITE)) !=
                (fptr->mode & FMODE_READWRITE)) {
                rb_raise(rb_eArgError,
                         "%s can't change access mode from \"%s\" to \"%s\"",
                         PREP_STDIO_NAME(fptr), rb_io_fmode_modestr(fptr->mode),
                         rb_io_fmode_modestr(fmode));
            }
            fptr->mode = fmode;
            fptr->encs = convconfig;
        }
        else {
            oflags = rb_io_fmode_oflags(fptr->mode);
        }

        fptr->pathv = fname;
        if (fptr->fd < 0) {
            fptr->fd = rb_sysopen(fptr->pathv, oflags, 0666);
            fptr->stdio_file = 0;
            return file;
        }

        if (fptr->mode & FMODE_WRITABLE) {
            if (io_fflush(fptr) < 0)
                rb_sys_fail_on_write(fptr);
        }
        fptr->rbuf.off = fptr->rbuf.len = 0;

        if (fptr->stdio_file) {
            int e = rb_freopen(rb_str_encode_ospath(fptr->pathv),
                               rb_io_oflags_modestr(oflags),
                               fptr->stdio_file);
            if (e) rb_syserr_fail_path(e, fptr->pathv);
            fptr->fd = fileno(fptr->stdio_file);
            rb_fd_fix_cloexec(fptr->fd);
    #ifdef USE_SETVBUF
            if (setvbuf(fptr->stdio_file, NULL, _IOFBF, 0) != 0)
                rb_warn("setvbuf() can't be honoured for %"PRIsVALUE, fptr->pathv);
    #endif
            if (fptr->stdio_file == stderr) {
                if (setvbuf(fptr->stdio_file, NULL, _IONBF, BUFSIZ) != 0)
                    rb_warn("setvbuf() can't be honoured for %"PRIsVALUE, fptr->pathv);
            }
            else if (fptr->stdio_file == stdout && isatty(fptr->fd)) {
                if (setvbuf(fptr->stdio_file, NULL, _IOLBF, BUFSIZ) != 0)
                    rb_warn("setvbuf() can't be honoured for %"PRIsVALUE, fptr->pathv);
            }
        }
        else {
            int tmpfd = rb_sysopen(fptr->pathv, oflags, 0666);
            int err = 0;
            if (rb_cloexec_dup2(tmpfd, fptr->fd) < 0)
                err = errno;
            (void)close(tmpfd);
            if (err) {
                rb_syserr_fail_path(err, fptr->pathv);
            }
        }

        return file;
    }

Reassociates the stream with another stream, which may be of a different class. This method may be used to redirect an existing stream to a new destination.

With argument `other_io` given, reassociates with that stream:

    # Redirect $stdin from a file.
    f = File.open('t.txt')
    $stdin.reopen(f)
    f.close

    # Redirect $stdout to a file.
    f = File.open('t.tmp', 'w')
    $stdout.reopen(f)
    f.close

With argument `path` given, reassociates with a new stream to that file path:

    $stdin.reopen('t.txt')
    $stdout.reopen('t.tmp', 'w')

Optional keyword arguments `opts` specify:

- Open Options.

- Encoding options.

rewind → 0
Source

    static VALUE
    rb_io_rewind(VALUE io)
    {
        rb_io_t *fptr;

        GetOpenFile(io, fptr);
        if (io_seek(fptr, 0L, 0) < 0 && errno) rb_sys_fail_path(fptr->pathv);
        if (io == ARGF.current_file) {
            ARGF.lineno -= fptr->lineno;
        }
        fptr->lineno = 0;
        if (fptr->readconv) {
            clear_readconv(fptr);
        }

        return INT2FIX(0);
    }

Repositions the stream to its beginning, setting both the position and the line number to zero; see Position and Line Number:

    f = File.open('t.txt')
    f.tell     # => 0
    f.lineno   # => 0
    f.gets     # => "First line\n"
    f.tell     # => 12
    f.lineno   # => 1
    f.rewind   # => 0
    f.tell     # => 0
    f.lineno   # => 0
    f.close

Note that this method cannot be used with streams such as pipes, ttys, and sockets.

scroll_backward(n) → io
Source

    static VALUE
    console_scroll_backward(VALUE io, VALUE val)
    {
        return console_scroll(io, -NUM2INT(val));
    }

Scrolls the entire scrolls backward `n` lines.

You must require ‘io/console’ to use this method.

scroll_forward(n) → io
Source

    static VALUE
    console_scroll_forward(VALUE io, VALUE val)
    {
        return console_scroll(io, +NUM2INT(val));
    }

Scrolls the entire scrolls forward `n` lines.

You must require ‘io/console’ to use this method.

seek(offset, whence = IO::SEEK_SET) → 0
Source

    static VALUE
    rb_io_seek_m(int argc, VALUE *argv, VALUE io)
    {
        VALUE offset, ptrname;
        int whence = SEEK_SET;

        if (rb_scan_args(argc, argv, "11", &offset, &ptrname) == 2) {
            whence = interpret_seek_whence(ptrname);
        }

        return rb_io_seek(io, offset, whence);
    }

Seeks to the position given by integer `offset` (see Position) and constant `whence`, which is one of:

- `:CUR` or `IO::SEEK_CUR`: Repositions the stream to its current position plus the given `offset`:

      f = File.open('t.txt')
      f.tell            # => 0
      f.seek(20, :CUR)  # => 0
      f.tell            # => 20
      f.seek(-10, :CUR) # => 0
      f.tell            # => 10
      f.close

- `:END` or `IO::SEEK_END`: Repositions the stream to its end plus the given `offset`:

      f = File.open('t.txt')
      f.tell            # => 0
      f.seek(0, :END)   # => 0  # Repositions to stream end.
      f.tell            # => 52
      f.seek(-20, :END) # => 0
      f.tell            # => 32
      f.seek(-40, :END) # => 0
      f.tell            # => 12
      f.close

- `:SET` or `IO:SEEK_SET`: Repositions the stream to the given `offset`:

      f = File.open('t.txt')
      f.tell            # => 0
      f.seek(20, :SET) # => 0
      f.tell           # => 20
      f.seek(40, :SET) # => 0
      f.tell           # => 40
      f.close

Related: `IO#pos=`, `IO#tell`.

set_encoding(ext_enc) → self
set_encoding(ext_enc, int_enc, **enc_opts) → self
set_encoding('ext_enc:int_enc', **enc_opts) → self
Source

    static VALUE
    rb_io_set_encoding(int argc, VALUE *argv, VALUE io)
    {
        rb_io_t *fptr;
        VALUE v1, v2, opt;

        if (!RB_TYPE_P(io, T_FILE)) {
            return forward(io, id_set_encoding, argc, argv);
        }

        argc = rb_scan_args(argc, argv, "11:", &v1, &v2, &opt);
        GetOpenFile(io, fptr);
        io_encoding_set(fptr, v1, v2, opt);
        return io;
    }

See Encodings.

Argument `ext_enc`, if given, must be an `Encoding` object or a `String` with the encoding name; it is assigned as the encoding for the stream.

Argument `int_enc`, if given, must be an `Encoding` object or a `String` with the encoding name; it is assigned as the encoding for the internal string.

Argument `'ext_enc:int_enc'`, if given, is a string containing two colon-separated encoding names; corresponding `Encoding` objects are assigned as the external and internal encodings for the stream.

If the external encoding of a string is binary/ASCII-8BIT, the internal encoding of the string is set to nil, since no transcoding is needed.

Optional keyword arguments `enc_opts` specify Encoding options.

set_encoding_by_bom → encoding or nil
Source

    static VALUE
    rb_io_set_encoding_by_bom(VALUE io)
    {
        rb_io_t *fptr;

        GetOpenFile(io, fptr);
        if (!(fptr->mode & FMODE_BINMODE)) {
            rb_raise(rb_eArgError, "ASCII incompatible encoding needs binmode");
        }
        if (fptr->encs.enc2) {
            rb_raise(rb_eArgError, "encoding conversion is set");
        }
        else if (fptr->encs.enc && fptr->encs.enc != rb_ascii8bit_encoding()) {
            rb_raise(rb_eArgError, "encoding is set to %s already",
                     rb_enc_name(fptr->encs.enc));
        }
        if (!io_set_encoding_by_bom(io)) return Qnil;
        return rb_enc_from_encoding(fptr->encs.enc);
    }

If the stream begins with a BOM (byte order marker), consumes the BOM and sets the external encoding accordingly; returns the result encoding if found, or `nil` otherwise:

    File.write('t.tmp', "\u{FEFF}abc")
    io = File.open('t.tmp', 'rb')
    io.set_encoding_by_bom # => #<Encoding:UTF-8>
    io.close

    File.write('t.tmp', 'abc')
    io = File.open('t.tmp', 'rb')
    io.set_encoding_by_bom # => nil
    io.close

Raises an exception if the stream is not binmode or its encoding has already been set.

stat → stat
Source

    static VALUE
    rb_io_stat(VALUE obj)
    {
        rb_io_t *fptr;
        struct stat st;

        GetOpenFile(obj, fptr);
        if (fstat(fptr->fd, &st) == -1) {
            rb_sys_fail_path(fptr->pathv);
        }
        return rb_stat_new(&st);
    }

Returns status information for ios as an object of type `File::Stat`.

    f = File.new("testfile")
    s = f.stat
    "%o" % s.mode   #=> "100644"
    s.blksize       #=> 4096
    s.atime         #=> Wed Apr 09 08:53:54 CDT 2003

sync → true or false
Source

    static VALUE
    rb_io_sync(VALUE io)
    {
        rb_io_t *fptr;

        io = GetWriteIO(io);
        GetOpenFile(io, fptr);
        return RBOOL(fptr->mode & FMODE_SYNC);
    }

Returns the current sync mode of the stream. When sync mode is true, all output is immediately flushed to the underlying operating system and is not buffered by Ruby internally. See also `fsync`.

    f = File.open('t.tmp', 'w')
    f.sync # => false
    f.sync = true
    f.sync # => true
    f.close

sync = boolean → boolean
Source

    static VALUE
    rb_io_set_sync(VALUE io, VALUE sync)
    {
        rb_io_t *fptr;

        io = GetWriteIO(io);
        GetOpenFile(io, fptr);
        if (RTEST(sync)) {
            fptr->mode |= FMODE_SYNC;
        }
        else {
            fptr->mode &= ~FMODE_SYNC;
        }
        return sync;
    }

Sets the sync mode for the stream to the given value; returns the given value.

Values for the sync mode:

- `true`: All output is immediately flushed to the underlying operating system and is not buffered internally.

- `false`: Output may be buffered internally.

Example;

    f = File.open('t.tmp', 'w')
    f.sync # => false
    f.sync = true
    f.sync # => true
    f.close

Related: `IO#fsync`.

sysread(maxlen) → string
sysread(maxlen, out_string) → string
Source

    static VALUE
    rb_io_sysread(int argc, VALUE *argv, VALUE io)
    {
        VALUE len, str;
        rb_io_t *fptr;
        long n, ilen;
        struct io_internal_read_struct iis;
        int shrinkable;

        rb_scan_args(argc, argv, "11", &len, &str);
        ilen = NUM2LONG(len);

        shrinkable = io_setstrbuf(&str, ilen);
        if (ilen == 0) return str;

        GetOpenFile(io, fptr);
        rb_io_check_byte_readable(fptr);

        if (READ_DATA_BUFFERED(fptr)) {
            rb_raise(rb_eIOError, "sysread for buffered IO");
        }

        rb_io_check_closed(fptr);

        io_setstrbuf(&str, ilen);
        iis.th = rb_thread_current();
        iis.fptr = fptr;
        iis.nonblock = 0;
        iis.fd = fptr->fd;
        iis.buf = RSTRING_PTR(str);
        iis.capa = ilen;
        iis.timeout = NULL;
        n = io_read_memory_locktmp(str, &iis);

        if (n < 0) {
            rb_sys_fail_path(fptr->pathv);
        }

        io_set_read_length(str, n, shrinkable);

        if (n == 0 && ilen > 0) {
            rb_eof_error();
        }

        return str;
    }

Behaves like `IO#readpartial`, except that it uses low-level system functions.

This method should not be used with other stream-reader methods.

sysseek(offset, whence = IO::SEEK_SET) → integer
Source

    static VALUE
    rb_io_sysseek(int argc, VALUE *argv, VALUE io)
    {
        VALUE offset, ptrname;
        int whence = SEEK_SET;
        rb_io_t *fptr;
        rb_off_t pos;

        if (rb_scan_args(argc, argv, "11", &offset, &ptrname) == 2) {
            whence = interpret_seek_whence(ptrname);
        }
        pos = NUM2OFFT(offset);
        GetOpenFile(io, fptr);
        if ((fptr->mode & FMODE_READABLE) &&
            (READ_DATA_BUFFERED(fptr) || READ_CHAR_PENDING(fptr))) {
            rb_raise(rb_eIOError, "sysseek for buffered IO");
        }
        if ((fptr->mode & FMODE_WRITABLE) && fptr->wbuf.len) {
            rb_warn("sysseek for buffered IO");
        }
        errno = 0;
        pos = lseek(fptr->fd, pos, whence);
        if (pos < 0 && errno) rb_sys_fail_path(fptr->pathv);

        return OFFT2NUM(pos);
    }

Behaves like `IO#seek`, except that it:

- Uses low-level system functions.

- Returns the new position.

syswrite(object) → integer
Source

    static VALUE
    rb_io_syswrite(VALUE io, VALUE str)
    {
        VALUE tmp;
        rb_io_t *fptr;
        long n, len;
        const char *ptr;

        if (!RB_TYPE_P(str, T_STRING))
            str = rb_obj_as_string(str);

        io = GetWriteIO(io);
        GetOpenFile(io, fptr);
        rb_io_check_writable(fptr);

        if (fptr->wbuf.len) {
            rb_warn("syswrite for buffered IO");
        }

        tmp = rb_str_tmp_frozen_acquire(str);
        RSTRING_GETMEM(tmp, ptr, len);
        n = rb_io_write_memory(fptr, ptr, len);
        if (n < 0) rb_sys_fail_path(fptr->pathv);
        rb_str_tmp_frozen_release(str, tmp);

        return LONG2FIX(n);
    }

Writes the given `object` to self, which must be opened for writing (see Modes); returns the number bytes written. If `object` is not a string is converted via method to_s:

    f = File.new('t.tmp', 'w')
    f.syswrite('foo') # => 3
    f.syswrite(30)    # => 2
    f.syswrite(:foo)  # => 3
    f.close

This methods should not be used with other stream-writer methods.

tell → integer
Source

    static VALUE
    rb_io_tell(VALUE io)
    {
        rb_io_t *fptr;
        rb_off_t pos;

        GetOpenFile(io, fptr);
        pos = io_tell(fptr);
        if (pos < 0 && errno) rb_sys_fail_path(fptr->pathv);
        pos -= fptr->rbuf.len;
        return OFFT2NUM(pos);
    }

Returns the current position (in bytes) in `self` (see Position):

    f = File.open('t.txt')
    f.tell # => 0
    f.gets # => "First line\n"
    f.tell # => 12
    f.close

Related: `IO#pos=`, `IO#seek`.

Also aliased as: pos
timeout → duration or nil
Source

    VALUE
    rb_io_timeout(VALUE self)
    {
        rb_io_t *fptr = rb_io_get_fptr(self);

        return fptr->timeout;
    }

Get the internal timeout duration or nil if it was not set.

timeout = duration → duration
timeout = nil → nil
Source

    VALUE
    rb_io_set_timeout(VALUE self, VALUE timeout)
    {
        // Validate it:
        if (RTEST(timeout)) {
            rb_time_interval(timeout);
        }

        rb_io_t *fptr = rb_io_get_fptr(self);

        fptr->timeout = timeout;

        return self;
    }

Sets the internal timeout to the specified duration or nil. The timeout applies to all blocking operations where possible.

When the operation performs longer than the timeout set, `IO::TimeoutError` is raised.

This affects the following methods (but is not limited to): `gets`, `puts`, `read`, `write`, `wait_readable` and `wait_writable`. This also affects blocking socket operations like `Socket#accept` and `Socket#connect`.

Some operations like `File#open` and `IO#close` are not affected by the timeout. A timeout during a write operation may leave the `IO` in an inconsistent state, e.g. data was partially written. Generally speaking, a timeout is a last ditch effort to prevent an application from hanging on slow I/O operations, such as those that occur during a slowloris attack.

to_i
Alias for: fileno
to_io → self
Source

    static VALUE
    rb_io_to_io(VALUE io)
    {
        return io;
    }

Returns `self`.

to_path
Alias for: path
tty?
Alias for: isatty
ttyname → string or nil
Source

    static VALUE
    console_ttyname(VALUE io)
    {
        int fd = rb_io_descriptor(io);
        if (!isatty(fd)) return Qnil;
    # if defined _WIN32
        return rb_usascii_str_new_lit("con");
    # elif defined HAVE_TTYNAME_R
        {
            char termname[1024], *tn = termname;
            size_t size = sizeof(termname);
            int e;
            if (ttyname_r(fd, tn, size) == 0)
                return rb_interned_str_cstr(tn);
            if ((e = errno) == ERANGE) {
                VALUE s = rb_str_new(0, size);
                while (1) {
                    tn = RSTRING_PTR(s);
                    size = rb_str_capacity(s);
                    if (ttyname_r(fd, tn, size) == 0) {
                        return rb_str_to_interned_str(rb_str_resize(s, strlen(tn)));
                    }
                    if ((e = errno) != ERANGE) break;
                    if ((size *= 2) >= INT_MAX/2) break;
                    rb_str_resize(s, size);
                }
            }
            rb_syserr_fail_str(e, rb_sprintf("ttyname_r(%d)", fd));
            UNREACHABLE_RETURN(Qnil);
        }
    # elif defined HAVE_TTYNAME
        {
            const char *tn = ttyname(fd);
            if (!tn) {
                int e = errno;
                rb_syserr_fail_str(e, rb_sprintf("ttyname(%d)", fd));
            }
            return rb_interned_str_cstr(tn);
        }
    # else
    #   error No ttyname function
    # endif
    }

Returns name of associated terminal (tty) if `io` is not a tty. Returns `nil` otherwise.

ungetbyte(integer) → nil
ungetbyte(string) → nil
Source

    VALUE
    rb_io_ungetbyte(VALUE io, VALUE b)
    {
        rb_io_t *fptr;

        GetOpenFile(io, fptr);
        rb_io_check_byte_readable(fptr);
        switch (TYPE(b)) {
          case T_NIL:
            return Qnil;
          case T_FIXNUM:
          case T_BIGNUM: ;
            VALUE v = rb_int_modulo(b, INT2FIX(256));
            unsigned char c = NUM2INT(v) & 0xFF;
            b = rb_str_new((const char *)&c, 1);
            break;
          default:
            StringValue(b);
        }
        io_ungetbyte(b, fptr);
        return Qnil;
    }

Pushes back (“unshifts”) the given data onto the stream’s buffer, placing the data so that it is next to be read; returns `nil`. See Byte IO.

Note that:

- Calling the method has no effect with unbuffered reads (such as `IO#sysread`).

- Calling `rewind` on the stream discards the pushed-back data.

When argument `integer` is given, uses only its low-order byte:

    File.write('t.tmp', '012')
    f = File.open('t.tmp')
    f.ungetbyte(0x41)   # => nil
    f.read              # => "A012"
    f.rewind
    f.ungetbyte(0x4243) # => nil
    f.read              # => "C012"
    f.close

When argument `string` is given, uses all bytes:

    File.write('t.tmp', '012')
    f = File.open('t.tmp')
    f.ungetbyte('A')    # => nil
    f.read              # => "A012"
    f.rewind
    f.ungetbyte('BCDE') # => nil
    f.read              # => "BCDE012"
    f.close

ungetc(integer) → nil
ungetc(string) → nil
Source

    VALUE
    rb_io_ungetc(VALUE io, VALUE c)
    {
        rb_io_t *fptr;
        long len;

        GetOpenFile(io, fptr);
        rb_io_check_char_readable(fptr);
        if (FIXNUM_P(c)) {
            c = rb_enc_uint_chr(FIX2UINT(c), io_read_encoding(fptr));
        }
        else if (RB_BIGNUM_TYPE_P(c)) {
            c = rb_enc_uint_chr(NUM2UINT(c), io_read_encoding(fptr));
        }
        else {
            StringValue(c);
        }
        if (NEED_READCONV(fptr)) {
            SET_BINARY_MODE(fptr);
            len = RSTRING_LEN(c);
    #if SIZEOF_LONG > SIZEOF_INT
            if (len > INT_MAX)
                rb_raise(rb_eIOError, "ungetc failed");
    #endif
            make_readconv(fptr, (int)len);
            if (fptr->cbuf.capa - fptr->cbuf.len < len)
                rb_raise(rb_eIOError, "ungetc failed");
            if (fptr->cbuf.off < len) {
                MEMMOVE(fptr->cbuf.ptr+fptr->cbuf.capa-fptr->cbuf.len,
                        fptr->cbuf.ptr+fptr->cbuf.off,
                        char, fptr->cbuf.len);
                fptr->cbuf.off = fptr->cbuf.capa-fptr->cbuf.len;
            }
            fptr->cbuf.off -= (int)len;
            fptr->cbuf.len += (int)len;
            MEMMOVE(fptr->cbuf.ptr+fptr->cbuf.off, RSTRING_PTR(c), char, len);
        }
        else {
            NEED_NEWLINE_DECORATOR_ON_READ_CHECK(fptr);
            io_ungetbyte(c, fptr);
        }
        return Qnil;
    }

Pushes back (“unshifts”) the given data onto the stream’s buffer, placing the data so that it is next to be read; returns `nil`. See Character IO.

Note that:

- Calling the method has no effect with unbuffered reads (such as `IO#sysread`).

- Calling `rewind` on the stream discards the pushed-back data.

When argument `integer` is given, interprets the integer as a character:

    File.write('t.tmp', '012')
    f = File.open('t.tmp')
    f.ungetc(0x41)     # => nil
    f.read             # => "A012"
    f.rewind
    f.ungetc(0x0442)   # => nil
    f.getc.ord         # => 1090
    f.close

When argument `string` is given, uses all characters:

    File.write('t.tmp', '012')
    f = File.open('t.tmp')
    f.ungetc('A')      # => nil
    f.read      # => "A012"
    f.rewind
    f.ungetc("\u0442\u0435\u0441\u0442") # => nil
    f.getc.ord      # => 1090
    f.getc.ord      # => 1077
    f.getc.ord      # => 1089
    f.getc.ord      # => 1090
    f.close

wait(events, timeout) → event mask, false or nil
wait(timeout = nil, mode = :read) → self, true, or false
Source

    static VALUE
    io_wait(int argc, VALUE *argv, VALUE io)
    {
    #ifndef HAVE_RB_IO_WAIT
        rb_io_t *fptr;
        struct timeval timerec;
        struct timeval *tv = NULL;
        int event = 0;
        int i;

        GetOpenFile(io, fptr);
        for (i = 0; i < argc; ++i) {
            if (SYMBOL_P(argv[i])) {
                event |= wait_mode_sym(argv[i]);
            }
            else {
                *(tv = &timerec) = rb_time_interval(argv[i]);
            }
        }
        /* rb_time_interval() and might_mode() might convert the argument */
        rb_io_check_closed(fptr);
        if (!event) event = RB_WAITFD_IN;
        if ((event & RB_WAITFD_IN) && rb_io_read_pending(fptr))
            return Qtrue;
        if (wait_for_single_fd(fptr, event, tv))
            return io;
        return Qnil;
    #else
        VALUE timeout = Qundef;
        rb_io_event_t events = 0;
        int i, return_io = 0;

        /* The documented signature for this method is actually incorrect.
         * A single timeout is allowed in any position, and multiple symbols can be given.
         * Whether this is intentional or not, I don't know, and as such I consider this to
         * be a legacy/slow path. */
        if (argc != 2 || (RB_SYMBOL_P(argv[0]) || RB_SYMBOL_P(argv[1]))) {
            /* We'd prefer to return the actual mask, but this form would return the io itself: */
            return_io = 1;

            /* Slow/messy path: */
            for (i = 0; i < argc; i += 1) {
                if (RB_SYMBOL_P(argv[i])) {
                    events |= wait_mode_sym(argv[i]);
                }
                else if (timeout == Qundef) {
                    rb_time_interval(timeout = argv[i]);
                }
                else {
                    rb_raise(rb_eArgError, "timeout given more than once");
                }
            }

            if (timeout == Qundef) timeout = Qnil;

            if (events == 0) {
                events = RUBY_IO_READABLE;
            }
        }
        else /* argc == 2 and neither are symbols */ {
            /* This is the fast path: */
            events = io_event_from_value(argv[0]);
            timeout = argv[1];
        }

        if (events & RUBY_IO_READABLE) {
            rb_io_t *fptr = NULL;
            RB_IO_POINTER(io, fptr);

            if (rb_io_read_pending(fptr)) {
                /* This was the original behaviour: */
                if (return_io) return Qtrue;
                /* New behaviour always returns an event mask: */
                else return RB_INT2NUM(RUBY_IO_READABLE);
            }
        }

        return io_wait_event(io, events, timeout, return_io);
    #endif
    }

Waits until the `IO` becomes ready for the specified events and returns the subset of events that become ready, or a falsy value when times out.

The events can be a bit mask of `IO::READABLE`, `IO::WRITABLE` or `IO::PRIORITY`.

Returns a truthy value immediately when buffered data is available.

Optional parameter `mode` is one of `:read`, `:write`, or `:read_write`.

You must require ‘io/wait’ to use this method.

Also aliased as: wait
wait_priority → truthy or falsy
wait_priority(timeout) → truthy or falsy
Source

    static VALUE
    io_wait_priority(int argc, VALUE *argv, VALUE io)
    {
        rb_io_t *fptr = NULL;

        RB_IO_POINTER(io, fptr);
        rb_io_check_readable(fptr);

        if (rb_io_read_pending(fptr)) return Qtrue;

        rb_check_arity(argc, 0, 1);
        VALUE timeout = argc == 1 ? argv[0] : Qnil;

        return io_wait_event(io, RUBY_IO_PRIORITY, timeout, 1);
    }

Waits until `IO` is priority and returns a truthy value or a falsy value when times out. Priority data is sent and received using the Socket::MSG_OOB flag and is typically limited to streams.

You must require ‘io/wait’ to use this method.

Also aliased as: wait_priority
wait_readable → truthy or falsy
wait_readable(timeout) → truthy or falsy
Source

    static VALUE
    io_wait_readable(int argc, VALUE *argv, VALUE io)
    {
        rb_io_t *fptr;
    #ifndef HAVE_RB_IO_WAIT
        struct timeval timerec;
        struct timeval *tv;
    #endif

        GetOpenFile(io, fptr);
        rb_io_check_readable(fptr);

    #ifndef HAVE_RB_IO_WAIT
        tv = get_timeout(argc, argv, &timerec);
    #endif
        if (rb_io_read_pending(fptr)) return Qtrue;

    #ifndef HAVE_RB_IO_WAIT
        if (wait_for_single_fd(fptr, RB_WAITFD_IN, tv)) {
            return io;
        }
        return Qnil;
    #else
        rb_check_arity(argc, 0, 1);
        VALUE timeout = (argc == 1 ? argv[0] : Qnil);

        return io_wait_event(io, RUBY_IO_READABLE, timeout, 1);
    #endif
    }

Waits until `IO` is readable and returns a truthy value, or a falsy value when times out. Returns a truthy value immediately when buffered data is available.

You must require ‘io/wait’ to use this method.

Also aliased as: wait_readable
wait_writable → truthy or falsy
wait_writable(timeout) → truthy or falsy
Source

    static VALUE
    io_wait_writable(int argc, VALUE *argv, VALUE io)
    {
        rb_io_t *fptr;
    #ifndef HAVE_RB_IO_WAIT
        struct timeval timerec;
        struct timeval *tv;
    #endif

        GetOpenFile(io, fptr);
        rb_io_check_writable(fptr);

    #ifndef HAVE_RB_IO_WAIT
        tv = get_timeout(argc, argv, &timerec);
        if (wait_for_single_fd(fptr, RB_WAITFD_OUT, tv)) {
            return io;
        }
        return Qnil;
    #else
        rb_check_arity(argc, 0, 1);
        VALUE timeout = (argc == 1 ? argv[0] : Qnil);

        return io_wait_event(io, RUBY_IO_WRITABLE, timeout, 1);
    #endif
    }

Waits until `IO` is writable and returns a truthy value or a falsy value when times out.

You must require ‘io/wait’ to use this method.

Also aliased as: wait_writable
winsize → [rows, columns]
Source

    static VALUE
    console_winsize(VALUE io)
    {
        rb_console_size_t ws;
        int fd = GetWriteFD(io);
        if (!getwinsize(fd, &ws)) sys_fail(io);
        return rb_assoc_new(INT2NUM(winsize_row(&ws)), INT2NUM(winsize_col(&ws)));
    }

Returns console size.

You must require ‘io/console’ to use this method.

winsize = [rows, columns]
Source

    static VALUE
    console_set_winsize(VALUE io, VALUE size)
    {
        rb_console_size_t ws;
    #if defined _WIN32
        HANDLE wh;
        int newrow, newcol;
        BOOL ret;
    #endif
        VALUE row, col, xpixel, ypixel;
        const VALUE *sz;
        long sizelen;
        int fd;

        size = rb_Array(size);
        if ((sizelen = RARRAY_LEN(size)) != 2 && sizelen != 4) {
            rb_raise(rb_eArgError, "wrong number of arguments (given %ld, expected 2 or 4)", sizelen);
        }
        sz = RARRAY_CONST_PTR(size);
        row = sz[0], col = sz[1], xpixel = ypixel = Qnil;
        if (sizelen == 4) xpixel = sz[2], ypixel = sz[3];
        fd = GetWriteFD(io);
    #if defined TIOCSWINSZ
        ws.ws_row = ws.ws_col = ws.ws_xpixel = ws.ws_ypixel = 0;
    #define SET(m) ws.ws_##m = NIL_P(m) ? 0 : (unsigned short)NUM2UINT(m)
        SET(row);
        SET(col);
        SET(xpixel);
        SET(ypixel);
    #undef SET
        if (!setwinsize(fd, &ws)) sys_fail(io);
    #elif defined _WIN32
        wh = (HANDLE)rb_w32_get_osfhandle(fd);
    #define SET(m) new##m = NIL_P(m) ? 0 : (unsigned short)NUM2UINT(m)
        SET(row);
        SET(col);
    #undef SET
        if (!NIL_P(xpixel)) (void)NUM2UINT(xpixel);
        if (!NIL_P(ypixel)) (void)NUM2UINT(ypixel);
        if (!GetConsoleScreenBufferInfo(wh, &ws)) {
            rb_syserr_fail(LAST_ERROR, "GetConsoleScreenBufferInfo");
        }
        ws.dwSize.X = newcol;
        ret = SetConsoleScreenBufferSize(wh, ws.dwSize);
        ws.srWindow.Left = 0;
        ws.srWindow.Top = 0;
        ws.srWindow.Right = newcol-1;
        ws.srWindow.Bottom = newrow-1;
        if (!SetConsoleWindowInfo(wh, TRUE, &ws.srWindow)) {
            rb_syserr_fail(LAST_ERROR, "SetConsoleWindowInfo");
        }
        /* retry when shrinking buffer after shrunk window */
        if (!ret && !SetConsoleScreenBufferSize(wh, ws.dwSize)) {
            rb_syserr_fail(LAST_ERROR, "SetConsoleScreenBufferInfo");
        }
        /* remove scrollbar if possible */
        if (!SetConsoleWindowInfo(wh, TRUE, &ws.srWindow)) {
            rb_syserr_fail(LAST_ERROR, "SetConsoleWindowInfo");
        }
    #endif
        return io;
    }

Tries to set console size. The effect depends on the platform and the running environment.

You must require ‘io/console’ to use this method.

write(*objects) → integer
Source

    static VALUE
    io_write_m(int argc, VALUE *argv, VALUE io)
    {
        if (argc != 1) {
            return io_writev(argc, argv, io);
        }
        else {
            VALUE str = argv[0];
            return io_write(io, str, 0);
        }
    }

Writes each of the given `objects` to `self`, which must be opened for writing (see Access Modes); returns the total number bytes written; each of `objects` that is not a string is converted via method `to_s`:

    $stdout.write('Hello', ', ', 'World!', "\n") # => 14
    $stdout.write('foo', :bar, 2, "\n")          # => 8

Output:

    Hello, World!
    foobar2

Related: `IO#read`.

write_nonblock(string) → integer
write_nonblock(string [, options]) → integer
Source

    # File io.rb, line 120
    def write_nonblock(buf, exception: true)
      Primitive.io_write_nonblock(buf, exception)
    end

Writes the given string to ios using the write(2) system call after O_NONBLOCK is set for the underlying file descriptor.

It returns the number of bytes written.

`write_nonblock` just calls the write(2) system call. It causes all errors the write(2) system call causes: Errno::EWOULDBLOCK, Errno::EINTR, etc. The result may also be smaller than string.length (partial write). The caller should care such errors and partial write.

If the exception is Errno::EWOULDBLOCK or Errno::EAGAIN, it is extended by `IO::WaitWritable`. So `IO::WaitWritable` can be used to rescue the exceptions for retrying write_nonblock.

    # Creates a pipe.
    r, w = IO.pipe

    # write_nonblock writes only 65536 bytes and return 65536.
    # (The pipe size is 65536 bytes on this environment.)
    s = "a" * 100000
    p w.write_nonblock(s)     #=> 65536

    # write_nonblock cannot write a byte and raise EWOULDBLOCK (EAGAIN).
    p w.write_nonblock("b")   # Resource temporarily unavailable (Errno::EAGAIN)

If the write buffer is not empty, it is flushed at first.

When `write_nonblock` raises an exception kind of `IO::WaitWritable`, `write_nonblock` should not be called until io is writable for avoiding busy loop. This can be done as follows.

    begin
      result = io.write_nonblock(string)
    rescue IO::WaitWritable, Errno::EINTR
      IO.select(nil, [io])
      retry
    end

Note that this doesn’t guarantee to write all data in string. The length written is reported as result and it should be checked later.

On some platforms such as Windows, `write_nonblock` is not supported according to the kind of the `IO` object. In such cases, `write_nonblock` raises `Errno::EBADF`.

By specifying a keyword argument exception to `false`, you can indicate that `write_nonblock` should not raise an `IO::WaitWritable` exception, but return the symbol `:wait_writable` instead.