# module Open3

Module Open3 supports creating child processes with access to their $stdin, $stdout, and $stderr streams.

## What’s Here¶ ↑

Each of these methods executes a given command in a new process or subshell, or multiple commands in new processes and/or subshells:

- Each of these methods executes a single command in a process or subshell, accepts a string for input to $stdin, and returns string output from $stdout, $stderr, or both:

  - `Open3.capture2`: Executes the command; returns the string from $stdout.

  - `Open3.capture2e`: Executes the command; returns the string from merged $stdout and $stderr.

  - `Open3.capture3`: Executes the command; returns strings from $stdout and $stderr.

- Each of these methods executes a single command in a process or subshell, and returns pipes for $stdin, $stdout, and/or $stderr:

  - `Open3.popen2`: Executes the command; returns pipes for $stdin and $stdout.

  - `Open3.popen2e`: Executes the command; returns pipes for $stdin and merged $stdout and $stderr.

  - `Open3.popen3`: Executes the command; returns pipes for $stdin, $stdout, and $stderr.

- Each of these methods executes one or more commands in processes and/or subshells, returns pipes for the first $stdin, the last $stdout, or both:

  - `Open3.pipeline_r`: Returns a pipe for the last $stdout.

  - `Open3.pipeline_rw`: Returns pipes for the first $stdin and the last $stdout.

  - `Open3.pipeline_w`: Returns a pipe for the first $stdin.

  - `Open3.pipeline_start`: Does not wait for processes to complete.

  - `Open3.pipeline`: Waits for processes to complete.

Each of the methods above accepts:

- An optional hash of environment variable names and values; see Execution Environment.

- A required string argument that is a `command_line` or `exe_path`; see Argument command_line or exe_path.

- An optional hash of execution options; see Execution Options.

### Constants

VERSION

### Public Class Methods

capture2([env, ] command_line, options = {}) → [stdout_s, status]
capture2([env, ] exe_path, *args, options = {}) → [stdout_s, status]
Source

    # File lib/open3.rb, line 775
    def capture2(*cmd)
      if Hash === cmd.last
        opts = cmd.pop.dup
      else
        opts = {}
      end

      stdin_data = opts.delete(:stdin_data)
      binmode = opts.delete(:binmode)

      popen2(*cmd, opts) {|i, o, t|
        if binmode
          i.binmode
          o.binmode
        end
        out_reader = Thread.new { o.read }
        if stdin_data
          begin
            if stdin_data.respond_to? :readpartial
              IO.copy_stream(stdin_data, i)
            else
              i.write stdin_data
            end
          rescue Errno::EPIPE
          end
        end
        i.close
        [out_reader.value, t.value]
      }
    end

Basically a wrapper for `Open3.popen3` that:

- Creates a child process, by calling `Open3.popen3` with the given arguments (except for certain entries in hash `options`; see below).

- Returns as string `stdout_s` the standard output of the child process.

- Returns as `status` a `Process::Status` object that represents the exit status of the child process.

Returns the array `[stdout_s, status]`:

    stdout_s, status = Open3.capture2('echo "Foo"')
    # => ["Foo\n", #<Process::Status: pid 2326047 exit 0>]

Like `Process.spawn`, this method has potential security vulnerabilities if called with untrusted input; see Command Injection.

Unlike `Process.spawn`, this method waits for the child process to exit before returning, so the caller need not do so.

If the first argument is a hash, it becomes leading argument `env` in the call to `Open3.popen3`; see Execution Environment.

If the last argument is a hash, it becomes trailing argument `options` in the call to `Open3.popen3`; see Execution Options.

The hash `options` is given; two options have local effect in method `Open3.capture2`:

- If entry `options[:stdin_data]` exists, the entry is removed and its string value is sent to the command’s standard input:

      Open3.capture2('tee', stdin_data: 'Foo')

      # => ["Foo", #<Process::Status: pid 2326087 exit 0>]

- If entry `options[:binmode]` exists, the entry is removed and the internal streams are set to binary mode.

The single required argument is one of the following:

- `command_line` if it is a string, and if it begins with a shell reserved word or special built-in, or if it contains one or more metacharacters.

- `exe_path` otherwise.

Argument `command_line`

String argument `command_line` is a command line to be passed to a shell; it must begin with a shell reserved word, begin with a special built-in, or contain meta characters:

    Open3.capture2('if true; then echo "Foo"; fi') # Shell reserved word.
    # => ["Foo\n", #<Process::Status: pid 2326131 exit 0>]
    Open3.capture2('echo')                         # Built-in.
    # => ["\n", #<Process::Status: pid 2326139 exit 0>]
    Open3.capture2('date > date.tmp')              # Contains meta character.
    # => ["", #<Process::Status: pid 2326174 exit 0>]

The command line may also contain arguments and options for the command:

    Open3.capture2('echo "Foo"')
    # => ["Foo\n", #<Process::Status: pid 2326183 exit 0>]

Argument `exe_path`

Argument `exe_path` is one of the following:

- The string path to an executable to be called.

- A 2-element array containing the path to an executable and the string to be used as the name of the executing process.

Example:

    Open3.capture2('/usr/bin/date')
    # => ["Fri Sep 29 01:00:39 PM CDT 2023\n", #<Process::Status: pid 2326222 exit 0>]

Ruby invokes the executable directly, with no shell and no shell expansion:

    Open3.capture2('doesnt_exist') # Raises Errno::ENOENT

If one or more `args` is given, each is an argument or option to be passed to the executable:

    Open3.capture2('echo', 'C #')
    # => ["C #\n", #<Process::Status: pid 2326267 exit 0>]
    Open3.capture2('echo', 'hello', 'world')
    # => ["hello world\n", #<Process::Status: pid 2326299 exit 0>]

capture2e([env, ] command_line, options = {}) → [stdout_and_stderr_s, status]
capture2e([env, ] exe_path, *args, options = {}) → [stdout_and_stderr_s, status]
Source

    # File lib/open3.rb, line 902
    def capture2e(*cmd)
      if Hash === cmd.last
        opts = cmd.pop.dup
      else
        opts = {}
      end

      stdin_data = opts.delete(:stdin_data)
      binmode = opts.delete(:binmode)

      popen2e(*cmd, opts) {|i, oe, t|
        if binmode
          i.binmode
          oe.binmode
        end
        outerr_reader = Thread.new { oe.read }
        if stdin_data
          begin
            if stdin_data.respond_to? :readpartial
              IO.copy_stream(stdin_data, i)
            else
              i.write stdin_data
            end
          rescue Errno::EPIPE
          end
        end
        i.close
        [outerr_reader.value, t.value]
      }
    end

Basically a wrapper for `Open3.popen3` that:

- Creates a child process, by calling `Open3.popen3` with the given arguments (except for certain entries in hash `options`; see below).

- Returns as string `stdout_and_stderr_s` the merged standard output and standard error of the child process.

- Returns as `status` a `Process::Status` object that represents the exit status of the child process.

Returns the array `[stdout_and_stderr_s, status]`:

    stdout_and_stderr_s, status = Open3.capture2e('echo "Foo"')
    # => ["Foo\n", #<Process::Status: pid 2371692 exit 0>]

Like `Process.spawn`, this method has potential security vulnerabilities if called with untrusted input; see Command Injection.

Unlike `Process.spawn`, this method waits for the child process to exit before returning, so the caller need not do so.

If the first argument is a hash, it becomes leading argument `env` in the call to `Open3.popen3`; see Execution Environment.

If the last argument is a hash, it becomes trailing argument `options` in the call to `Open3.popen3`; see Execution Options.

The hash `options` is given; two options have local effect in method `Open3.capture2e`:

- If entry `options[:stdin_data]` exists, the entry is removed and its string value is sent to the command’s standard input:

      Open3.capture2e('tee', stdin_data: 'Foo')
      # => ["Foo", #<Process::Status: pid 2371732 exit 0>]

- If entry `options[:binmode]` exists, the entry is removed and the internal streams are set to binary mode.

The single required argument is one of the following:

- `command_line` if it is a string, and if it begins with a shell reserved word or special built-in, or if it contains one or more metacharacters.

- `exe_path` otherwise.

Argument `command_line`

String argument `command_line` is a command line to be passed to a shell; it must begin with a shell reserved word, begin with a special built-in, or contain meta characters:

    Open3.capture2e('if true; then echo "Foo"; fi') # Shell reserved word.
    # => ["Foo\n", #<Process::Status: pid 2371740 exit 0>]
    Open3.capture2e('echo')                         # Built-in.
    # => ["\n", #<Process::Status: pid 2371774 exit 0>]
    Open3.capture2e('date > date.tmp')              # Contains meta character.
    # => ["", #<Process::Status: pid 2371812 exit 0>]

The command line may also contain arguments and options for the command:

    Open3.capture2e('echo "Foo"')
    # => ["Foo\n", #<Process::Status: pid 2326183 exit 0>]

Argument `exe_path`

Argument `exe_path` is one of the following:

- The string path to an executable to be called.

- A 2-element array containing the path to an executable and the string to be used as the name of the executing process.

Example:

    Open3.capture2e('/usr/bin/date')
    # => ["Sat Sep 30 09:01:46 AM CDT 2023\n", #<Process::Status: pid 2371820 exit 0>]

Ruby invokes the executable directly, with no shell and no shell expansion:

    Open3.capture2e('doesnt_exist') # Raises Errno::ENOENT

If one or more `args` is given, each is an argument or option to be passed to the executable:

    Open3.capture2e('echo', 'C #')
    # => ["C #\n", #<Process::Status: pid 2371856 exit 0>]
    Open3.capture2e('echo', 'hello', 'world')
    # => ["hello world\n", #<Process::Status: pid 2371894 exit 0>]

capture3([env, ] command_line, options = {}) → [stdout_s, stderr_s, status]
capture3([env, ] exe_path, *args, options = {}) → [stdout_s, stderr_s, status]
Source

    # File lib/open3.rb, line 648
    def capture3(*cmd)
      if Hash === cmd.last
        opts = cmd.pop.dup
      else
        opts = {}
      end

      stdin_data = opts.delete(:stdin_data) || ''
      binmode = opts.delete(:binmode)

      popen3(*cmd, opts) {|i, o, e, t|
        if binmode
          i.binmode
          o.binmode
          e.binmode
        end
        out_reader = Thread.new { o.read }
        err_reader = Thread.new { e.read }
        begin
          if stdin_data.respond_to? :readpartial
            IO.copy_stream(stdin_data, i)
          else
            i.write stdin_data
          end
        rescue Errno::EPIPE
        end
        i.close
        [out_reader.value, err_reader.value, t.value]
      }
    end

Basically a wrapper for `Open3.popen3` that:

- Creates a child process, by calling `Open3.popen3` with the given arguments (except for certain entries in hash `options`; see below).

- Returns as strings `stdout_s` and `stderr_s` the standard output and standard error of the child process.

- Returns as `status` a `Process::Status` object that represents the exit status of the child process.

Returns the array `[stdout_s, stderr_s, status]`:

    stdout_s, stderr_s, status = Open3.capture3('echo "Foo"')
    # => ["Foo\n", "", #<Process::Status: pid 2281954 exit 0>]

Like `Process.spawn`, this method has potential security vulnerabilities if called with untrusted input; see Command Injection.

Unlike `Process.spawn`, this method waits for the child process to exit before returning, so the caller need not do so.

If the first argument is a hash, it becomes leading argument `env` in the call to `Open3.popen3`; see Execution Environment.

If the last argument is a hash, it becomes trailing argument `options` in the call to `Open3.popen3`; see Execution Options.

The hash `options` is given; two options have local effect in method `Open3.capture3`:

- If entry `options[:stdin_data]` exists, the entry is removed and its string value is sent to the command’s standard input:

      Open3.capture3('tee', stdin_data: 'Foo')
      # => ["Foo", "", #<Process::Status: pid 2319575 exit 0>]

- If entry `options[:binmode]` exists, the entry is removed and the internal streams are set to binary mode.

The single required argument is one of the following:

- `command_line` if it is a string, and if it begins with a shell reserved word or special built-in, or if it contains one or more metacharacters.

- `exe_path` otherwise.

Argument `command_line`

String argument `command_line` is a command line to be passed to a shell; it must begin with a shell reserved word, begin with a special built-in, or contain meta characters:

    Open3.capture3('if true; then echo "Foo"; fi') # Shell reserved word.
    # => ["Foo\n", "", #<Process::Status: pid 2282025 exit 0>]
    Open3.capture3('echo')                         # Built-in.
    # => ["\n", "", #<Process::Status: pid 2282092 exit 0>]
    Open3.capture3('date > date.tmp')              # Contains meta character.
    # => ["", "", #<Process::Status: pid 2282110 exit 0>]

The command line may also contain arguments and options for the command:

    Open3.capture3('echo "Foo"')
    # => ["Foo\n", "", #<Process::Status: pid 2282092 exit 0>]

Argument `exe_path`

Argument `exe_path` is one of the following:

- The string path to an executable to be called.

- A 2-element array containing the path to an executable and the string to be used as the name of the executing process.

Example:

    Open3.capture3('/usr/bin/date')
    # => ["Thu Sep 28 05:03:51 PM CDT 2023\n", "", #<Process::Status: pid 2282300 exit 0>]

Ruby invokes the executable directly, with no shell and no shell expansion:

    Open3.capture3('doesnt_exist') # Raises Errno::ENOENT

If one or more `args` is given, each is an argument or option to be passed to the executable:

    Open3.capture3('echo', 'C #')
    # => ["C #\n", "", #<Process::Status: pid 2282368 exit 0>]
    Open3.capture3('echo', 'hello', 'world')
    # => ["hello world\n", "", #<Process::Status: pid 2282372 exit 0>]

pipeline([env, ] *cmds, options = {}) → array_of_statuses
Source

    # File lib/open3.rb, line 1334
    def pipeline(*cmds)
      if Hash === cmds.last
        opts = cmds.pop.dup
      else
        opts = {}
      end

      pipeline_run(cmds, opts, [], []) {|ts|
        ts.map(&:value)
      }
    end

Basically a wrapper for `Process.spawn` that:

- Creates a child process for each of the given `cmds` by calling `Process.spawn`.

- Pipes the `stdout` from each child to the `stdin` of the next child, or, for the last child, to the caller’s `stdout`.

- Waits for the child processes to exit.

- Returns an array of `Process::Status` objects (one for each child).

Example:

    wait_threads = Open3.pipeline('ls', 'grep R')
    # => [#<Process::Status: pid 2139200 exit 0>, #<Process::Status: pid 2139202 exit 0>]

Output:

    Rakefile
    README.md

Like `Process.spawn`, this method has potential security vulnerabilities if called with untrusted input; see Command Injection.

If the first argument is a hash, it becomes leading argument `env` in each call to `Process.spawn`; see Execution Environment.

If the last argument is a hash, it becomes trailing argument `options` in each call to `Process.spawn`‘ see Execution Options.

Each remaining argument in `cmds` is one of:

- A `command_line`: a string that begins with a shell reserved word or special built-in, or contains one or more metacharacters.

- An `exe_path`: the string path to an executable to be called.

- An array containing a `command_line` or an `exe_path`, along with zero or more string arguments for the command.

See Argument command_line or exe_path.

pipeline_r([env, ] *cmds, options = {}) → [last_stdout, wait_threads]
Source

    # File lib/open3.rb, line 1104
    def pipeline_r(*cmds, &block)
      if Hash === cmds.last
        opts = cmds.pop.dup
      else
        opts = {}
      end

      out_r, out_w = IO.pipe
      opts[:out] = out_w

      pipeline_run(cmds, opts, [out_w], [out_r], &block)
    end

Basically a wrapper for `Process.spawn` that:

- Creates a child process for each of the given `cmds` by calling `Process.spawn`.

- Pipes the `stdout` from each child to the `stdin` of the next child, or, for the last child, to the caller’s `stdout`.

The method does not wait for child processes to exit, so the caller must do so.

With no block given, returns a 2-element array containing:

- The `stdout` stream of the last child process.

- An array of the wait threads for all of the child processes.

Example:

    last_stdout, wait_threads = Open3.pipeline_r('ls', 'grep R')
    # => [#<IO:fd 5>, [#<Process::Waiter:0x000055e8de2f9898 dead>, #<Process::Waiter:0x000055e8de2f94b0 sleep>]]
    puts last_stdout.read
    wait_threads.each do |wait_thread|
      wait_thread.join
    end

Output:

    Rakefile
    README.md

With a block given, calls the block with the `stdout` stream of the last child process, and an array of the wait processes:

    Open3.pipeline_r('ls', 'grep R') do |last_stdout, wait_threads|
      puts last_stdout.read
      wait_threads.each do |wait_thread|
        wait_thread.join
      end
    end

Output:

    Rakefile
    README.md

Like `Process.spawn`, this method has potential security vulnerabilities if called with untrusted input; see Command Injection.

If the first argument is a hash, it becomes leading argument `env` in each call to `Process.spawn`; see Execution Environment.

If the last argument is a hash, it becomes trailing argument `options` in each call to `Process.spawn`; see Execution Options.

Each remaining argument in `cmds` is one of:

- A `command_line`: a string that begins with a shell reserved word or special built-in, or contains one or more metacharacters.

- An `exe_path`: the string path to an executable to be called.

- An array containing a `command_line` or an `exe_path`, along with zero or more string arguments for the command.

See Argument command_line or exe_path.

pipeline_rw([env, ] *cmds, options = {}) → [first_stdin, last_stdout, wait_threads]
Source

    # File lib/open3.rb, line 1014
    def pipeline_rw(*cmds, &block)
      if Hash === cmds.last
        opts = cmds.pop.dup
      else
        opts = {}
      end

      in_r, in_w = IO.pipe
      opts[:in] = in_r
      in_w.sync = true

      out_r, out_w = IO.pipe
      opts[:out] = out_w

      pipeline_run(cmds, opts, [in_r, out_w], [in_w, out_r], &block)
    end

Basically a wrapper for `Process.spawn` that:

- Creates a child process for each of the given `cmds` by calling `Process.spawn`.

- Pipes the `stdout` from each child to the `stdin` of the next child, or, for the first child, from the caller’s `stdin`, or, for the last child, to the caller’s `stdout`.

The method does not wait for child processes to exit, so the caller must do so.

With no block given, returns a 3-element array containing:

- The `stdin` stream of the first child process.

- The `stdout` stream of the last child process.

- An array of the wait threads for all of the child processes.

Example:

    first_stdin, last_stdout, wait_threads = Open3.pipeline_rw('sort', 'cat -n')
    # => [#<IO:fd 20>, #<IO:fd 21>, [#<Process::Waiter:0x000055e8de29ab40 sleep>, #<Process::Waiter:0x000055e8de29a690 sleep>]]
    first_stdin.puts("foo\nbar\nbaz")
    first_stdin.close # Send EOF to sort.
    puts last_stdout.read
    wait_threads.each do |wait_thread|
      wait_thread.join
    end

Output:

    1 bar
    2 baz
    3 foo

With a block given, calls the block with the `stdin` stream of the first child, the `stdout` stream of the last child, and an array of the wait processes:

    Open3.pipeline_rw('sort', 'cat -n') do |first_stdin, last_stdout, wait_threads|
      first_stdin.puts "foo\nbar\nbaz"
      first_stdin.close # send EOF to sort.
      puts last_stdout.read
      wait_threads.each do |wait_thread|
        wait_thread.join
      end
    end

Output:

    1 bar
    2 baz
    3 foo

Like `Process.spawn`, this method has potential security vulnerabilities if called with untrusted input; see Command Injection.

If the first argument is a hash, it becomes leading argument `env` in each call to `Process.spawn`; see Execution Environment.

If the last argument is a hash, it becomes trailing argument `options` in each call to `Process.spawn`; see Execution Options.

Each remaining argument in `cmds` is one of:

- A `command_line`: a string that begins with a shell reserved word or special built-in, or contains one or more metacharacters.

- An `exe_path`: the string path to an executable to be called.

- An array containing a `command_line` or an `exe_path`, along with zero or more string arguments for the command.

See Argument command_line or exe_path.

pipeline_start([env, ] *cmds, options = {}) → [wait_threads]
Source

    # File lib/open3.rb, line 1272
    def pipeline_start(*cmds, &block)
      if Hash === cmds.last
        opts = cmds.pop.dup
      else
        opts = {}
      end

      if block
        pipeline_run(cmds, opts, [], [], &block)
      else
        ts, = pipeline_run(cmds, opts, [], [])
        ts
      end
    end

Basically a wrapper for `Process.spawn` that:

- Creates a child process for each of the given `cmds` by calling `Process.spawn`.

- Does not wait for child processes to exit.

With no block given, returns an array of the wait threads for all of the child processes.

Example:

    wait_threads = Open3.pipeline_start('ls', 'grep R')
    # => [#<Process::Waiter:0x000055e8de9d2bb0 run>, #<Process::Waiter:0x000055e8de9d2890 run>]
    wait_threads.each do |wait_thread|
      wait_thread.join
    end

Output:

    Rakefile
    README.md

With a block given, calls the block with an array of the wait processes:

    Open3.pipeline_start('ls', 'grep R') do |wait_threads|
      wait_threads.each do |wait_thread|
        wait_thread.join
      end
    end

Output:

    Rakefile
    README.md

Like `Process.spawn`, this method has potential security vulnerabilities if called with untrusted input; see Command Injection.

If the first argument is a hash, it becomes leading argument `env` in each call to `Process.spawn`; see Execution Environment.

If the last argument is a hash, it becomes trailing argument `options` in each call to `Process.spawn`; see Execution Options.

Each remaining argument in `cmds` is one of:

- A `command_line`: a string that begins with a shell reserved word or special built-in, or contains one or more metacharacters.

- An `exe_path`: the string path to an executable to be called.

- An array containing a `command_line` or an `exe_path`, along with zero or more string arguments for the command.

See Argument command_line or exe_path.

pipeline_w([env, ] *cmds, options = {}) → [first_stdin, wait_threads]
Source

    # File lib/open3.rb, line 1195
    def pipeline_w(*cmds, &block)
      if Hash === cmds.last
        opts = cmds.pop.dup
      else
        opts = {}
      end

      in_r, in_w = IO.pipe
      opts[:in] = in_r
      in_w.sync = true

      pipeline_run(cmds, opts, [in_r], [in_w], &block)
    end

Basically a wrapper for `Process.spawn` that:

- Creates a child process for each of the given `cmds` by calling `Process.spawn`.

- Pipes the `stdout` from each child to the `stdin` of the next child, or, for the first child, pipes the caller’s `stdout` to the child’s `stdin`.

The method does not wait for child processes to exit, so the caller must do so.

With no block given, returns a 2-element array containing:

- The `stdin` stream of the first child process.

- An array of the wait threads for all of the child processes.

Example:

    first_stdin, wait_threads = Open3.pipeline_w('sort', 'cat -n')
    # => [#<IO:fd 7>, [#<Process::Waiter:0x000055e8de928278 run>, #<Process::Waiter:0x000055e8de923e80 run>]]
    first_stdin.puts("foo\nbar\nbaz")
    first_stdin.close # Send EOF to sort.
    wait_threads.each do |wait_thread|
      wait_thread.join
    end

Output:

    1 bar
    2 baz
    3 foo

With a block given, calls the block with the `stdin` stream of the first child process, and an array of the wait processes:

    Open3.pipeline_w('sort', 'cat -n') do |first_stdin, wait_threads|
      first_stdin.puts("foo\nbar\nbaz")
      first_stdin.close # Send EOF to sort.
      wait_threads.each do |wait_thread|
        wait_thread.join
      end
    end

Output:

    1 bar
    2 baz
    3 foo

Like `Process.spawn`, this method has potential security vulnerabilities if called with untrusted input; see Command Injection.

If the first argument is a hash, it becomes leading argument `env` in each call to `Process.spawn`; see Execution Environment.

If the last argument is a hash, it becomes trailing argument `options` in each call to `Process.spawn`; see Execution Options.

Each remaining argument in `cmds` is one of:

- A `command_line`: a string that begins with a shell reserved word or special built-in, or contains one or more metacharacters.

- An `exe_path`: the string path to an executable to be called.

- An array containing a `command_line` or an `exe_path`, along with zero or more string arguments for the command.

See Argument command_line or exe_path.

popen2([env, ] command_line, options = {}) → [stdin, stdout, wait_thread]
popen2([env, ] exe_path, *args, options = {}) → [stdin, stdout, wait_thread]
popen2([env, ] command_line, options = {}) {|stdin, stdout, wait_thread| ... } → object
popen2([env, ] exe_path, *args, options = {}) {|stdin, stdout, wait_thread| ... } → object
Source

    # File lib/open3.rb, line 365
    def popen2(*cmd, &block)
      if Hash === cmd.last
        opts = cmd.pop.dup
      else
        opts = {}
      end

      in_r, in_w = IO.pipe
      opts[:in] = in_r
      in_w.sync = true

      out_r, out_w = IO.pipe
      opts[:out] = out_w

      popen_run(cmd, opts, [in_r, out_w], [in_w, out_r], &block)
    end

Basically a wrapper for `Process.spawn` that:

- Creates a child process, by calling `Process.spawn` with the given arguments.

- Creates streams `stdin` and `stdout`, which are the standard input and standard output streams in the child process.

- Creates thread `wait_thread` that waits for the child process to exit; the thread has method `pid`, which returns the process ID of the child process.

With no block given, returns the array `[stdin, stdout, wait_thread]`. The caller should close each of the two returned streams.

    stdin, stdout, wait_thread = Open3.popen2('echo')
    # => [#<IO:fd 6>, #<IO:fd 7>, #<Process::Waiter:0x00007f58d52dbe98 run>]
    stdin.close
    stdout.close
    wait_thread.pid   # => 2263572
    wait_thread.value # => #<Process::Status: pid 2263572 exit 0>

With a block given, calls the block with the three variables (two streams and the wait thread) and returns the block’s return value. The caller need not close the streams:

    Open3.popen2('echo') do |stdin, stdout, wait_thread|
      p stdin
      p stdout
      p wait_thread
      p wait_thread.pid
      p wait_thread.value
    end

Output:

    #<IO:fd 6>
    #<IO:fd 7>
    #<Process::Waiter:0x00007f58d59a34b0 sleep>
    2263636
    #<Process::Status: pid 2263636 exit 0>

Like `Process.spawn`, this method has potential security vulnerabilities if called with untrusted input; see Command Injection.

Unlike `Process.spawn`, this method waits for the child process to exit before returning, so the caller need not do so.

If the first argument is a hash, it becomes leading argument `env` in the call to `Process.spawn`; see Execution Environment.

If the last argument is a hash, it becomes trailing argument `options` in the call to `Process.spawn`; see Execution Options.

The single required argument is one of the following:

- `command_line` if it is a string, and if it begins with a shell reserved word or special built-in, or if it contains one or more metacharacters.

- `exe_path` otherwise.

Argument `command_line`

String argument `command_line` is a command line to be passed to a shell; it must begin with a shell reserved word, begin with a special built-in, or contain meta characters:

    Open3.popen2('if true; then echo "Foo"; fi') {|*args| p args } # Shell reserved word.
    Open3.popen2('echo') {|*args| p args }                         # Built-in.
    Open3.popen2('date > date.tmp') {|*args| p args }              # Contains meta character.

Output (similar for each call above):

    # => [#<IO:(closed)>, #<IO:(closed)>, #<Process::Waiter:0x00007f7577dfe410 dead>]

The command line may also contain arguments and options for the command:

    Open3.popen2('echo "Foo"') { |i, o, t| o.gets }
    "Foo\n"

Argument `exe_path`

Argument `exe_path` is one of the following:

- The string path to an executable to be called.

- A 2-element array containing the path to an executable and the string to be used as the name of the executing process.

Example:

    Open3.popen2('/usr/bin/date') { |i, o, t| o.gets }
    # => "Thu Sep 28 09:41:06 AM CDT 2023\n"

Ruby invokes the executable directly, with no shell and no shell expansion:

    Open3.popen2('doesnt_exist') { |i, o, t| o.gets } # Raises Errno::ENOENT

If one or more `args` is given, each is an argument or option to be passed to the executable:

    Open3.popen2('echo', 'C #') { |i, o, t| o.gets }
    # => "C #\n"
    Open3.popen2('echo', 'hello', 'world') { |i, o, t| o.gets }
    # => "hello world\n"

Related:

- `Open3.popen2e`: Makes the standard input and the merge of the standard output and standard error streams of the child process available as separate streams.

- `Open3.popen3`: Makes the standard input, standard output, and standard error streams of the child process available as separate streams.

popen2e([env, ] command_line, options = {}) → [stdin, stdout_and_stderr, wait_thread]
popen2e([env, ] exe_path, *args, options = {}) → [stdin, stdout_and_stderr, wait_thread]
popen2e([env, ] command_line, options = {}) {|stdin, stdout_and_stderr, wait_thread| ... } → object
popen2e([env, ] exe_path, *args, options = {}) {|stdin, stdout_and_stderr, wait_thread| ... } → object
Source

    # File lib/open3.rb, line 508
    def popen2e(*cmd, &block)
      if Hash === cmd.last
        opts = cmd.pop.dup
      else
        opts = {}
      end

      in_r, in_w = IO.pipe
      opts[:in] = in_r
      in_w.sync = true

      out_r, out_w = IO.pipe
      opts[[:out, :err]] = out_w

      popen_run(cmd, opts, [in_r, out_w], [in_w, out_r], &block)
    ensure
      if block
        in_r.close
        in_w.close
        out_r.close
        out_w.close
      end
    end

Basically a wrapper for `Process.spawn` that:

- Creates a child process, by calling `Process.spawn` with the given arguments.

- Creates streams `stdin`, `stdout_and_stderr`, which are the standard input and the merge of the standard output and standard error streams in the child process.

- Creates thread `wait_thread` that waits for the child process to exit; the thread has method `pid`, which returns the process ID of the child process.

With no block given, returns the array `[stdin, stdout_and_stderr, wait_thread]`. The caller should close each of the two returned streams.

    stdin, stdout_and_stderr, wait_thread = Open3.popen2e('echo')
    # => [#<IO:fd 6>, #<IO:fd 7>, #<Process::Waiter:0x00007f7577da4398 run>]
    stdin.close
    stdout_and_stderr.close
    wait_thread.pid   # => 2274600
    wait_thread.value # => #<Process::Status: pid 2274600 exit 0>

With a block given, calls the block with the three variables (two streams and the wait thread) and returns the block’s return value. The caller need not close the streams:

    Open3.popen2e('echo') do |stdin, stdout_and_stderr, wait_thread|
      p stdin
      p stdout_and_stderr
      p wait_thread
      p wait_thread.pid
      p wait_thread.value
    end

Output:

    #<IO:fd 6>
    #<IO:fd 7>
    #<Process::Waiter:0x00007f75777578c8 sleep>
    2274763
    #<Process::Status: pid 2274763 exit 0>

Like `Process.spawn`, this method has potential security vulnerabilities if called with untrusted input; see Command Injection.

Unlike `Process.spawn`, this method waits for the child process to exit before returning, so the caller need not do so.

If the first argument is a hash, it becomes leading argument `env` in the call to `Process.spawn`; see Execution Environment.

If the last argument is a hash, it becomes trailing argument `options` in the call to `Process.spawn`; see Execution Options.

The single required argument is one of the following:

- `command_line` if it is a string, and if it begins with a shell reserved word or special built-in, or if it contains one or more metacharacters.

- `exe_path` otherwise.

Argument `command_line`

String argument `command_line` is a command line to be passed to a shell; it must begin with a shell reserved word, begin with a special built-in, or contain meta characters:

    Open3.popen2e('if true; then echo "Foo"; fi') {|*args| p args } # Shell reserved word.
    Open3.popen2e('echo') {|*args| p args }                         # Built-in.
    Open3.popen2e('date > date.tmp') {|*args| p args }              # Contains meta character.

Output (similar for each call above):

    # => [#<IO:(closed)>, #<IO:(closed)>, #<Process::Waiter:0x00007f7577d8a1f0 dead>]

The command line may also contain arguments and options for the command:

    Open3.popen2e('echo "Foo"') { |i, o_and_e, t| o_and_e.gets }
    "Foo\n"

Argument `exe_path`

Argument `exe_path` is one of the following:

- The string path to an executable to be called.

- A 2-element array containing the path to an executable and the string to be used as the name of the executing process.

Example:

    Open3.popen2e('/usr/bin/date') { |i, o_and_e, t| o_and_e.gets }
    # => "Thu Sep 28 01:58:45 PM CDT 2023\n"

Ruby invokes the executable directly, with no shell and no shell expansion:

    Open3.popen2e('doesnt_exist') { |i, o_and_e, t| o_and_e.gets } # Raises Errno::ENOENT

If one or more `args` is given, each is an argument or option to be passed to the executable:

    Open3.popen2e('echo', 'C #') { |i, o_and_e, t| o_and_e.gets }
    # => "C #\n"
    Open3.popen2e('echo', 'hello', 'world') { |i, o_and_e, t| o_and_e.gets }
    # => "hello world\n"

Related:

- `Open3.popen2`: Makes the standard input and standard output streams of the child process available as separate streams, with no access to the standard error stream.

- `Open3.popen3`: Makes the standard input, standard output, and standard error streams of the child process available as separate streams.

popen3([env, ] command_line, options = {}) → [stdin, stdout, stderr, wait_thread]
popen3([env, ] exe_path, *args, options = {}) → [stdin, stdout, stderr, wait_thread]
popen3([env, ] command_line, options = {}) {|stdin, stdout, stderr, wait_thread| ... } → object
popen3([env, ] exe_path, *args, options = {}) {|stdin, stdout, stderr, wait_thread| ... } → object
Source

    # File lib/open3.rb, line 218
    def popen3(*cmd, &block)
      if Hash === cmd.last
        opts = cmd.pop.dup
      else
        opts = {}
      end

      in_r, in_w = IO.pipe
      opts[:in] = in_r
      in_w.sync = true

      out_r, out_w = IO.pipe
      opts[:out] = out_w

      err_r, err_w = IO.pipe
      opts[:err] = err_w

      popen_run(cmd, opts, [in_r, out_w, err_w], [in_w, out_r, err_r], &block)
    end

Basically a wrapper for `Process.spawn` that:

- Creates a child process, by calling `Process.spawn` with the given arguments.

- Creates streams `stdin`, `stdout`, and `stderr`, which are the standard input, standard output, and standard error streams in the child process.

- Creates thread `wait_thread` that waits for the child process to exit; the thread has method `pid`, which returns the process ID of the child process.

With no block given, returns the array `[stdin, stdout, stderr, wait_thread]`. The caller should close each of the three returned streams.

    stdin, stdout, stderr, wait_thread = Open3.popen3('echo')
    # => [#<IO:fd 8>, #<IO:fd 10>, #<IO:fd 12>, #<Process::Waiter:0x00007f58d5428f58 run>]
    stdin.close
    stdout.close
    stderr.close
    wait_thread.pid   # => 2210481
    wait_thread.value # => #<Process::Status: pid 2210481 exit 0>

With a block given, calls the block with the four variables (three streams and the wait thread) and returns the block’s return value. The caller need not close the streams:

    Open3.popen3('echo') do |stdin, stdout, stderr, wait_thread|
      p stdin
      p stdout
      p stderr
      p wait_thread
      p wait_thread.pid
      p wait_thread.value
    end

Output:

    #<IO:fd 6>
    #<IO:fd 7>
    #<IO:fd 9>
    #<Process::Waiter:0x00007f58d53606e8 sleep>
    2211047
    #<Process::Status: pid 2211047 exit 0>

Like `Process.spawn`, this method has potential security vulnerabilities if called with untrusted input; see Command Injection.

Unlike `Process.spawn`, this method waits for the child process to exit before returning, so the caller need not do so.

If the first argument is a hash, it becomes leading argument `env` in the call to `Process.spawn`; see Execution Environment.

If the last argument is a hash, it becomes trailing argument `options` in the call to `Process.spawn`; see Execution Options.

The single required argument is one of the following:

- `command_line` if it is a string, and if it begins with a shell reserved word or special built-in, or if it contains one or more metacharacters.

- `exe_path` otherwise.

Argument `command_line`

String argument `command_line` is a command line to be passed to a shell; it must begin with a shell reserved word, begin with a special built-in, or contain meta characters:

    Open3.popen3('if true; then echo "Foo"; fi') {|*args| p args } # Shell reserved word.
    Open3.popen3('echo') {|*args| p args }                         # Built-in.
    Open3.popen3('date > date.tmp') {|*args| p args }              # Contains meta character.

Output (similar for each call above):

    [#<IO:(closed)>, #<IO:(closed)>, #<IO:(closed)>, #<Process::Waiter:0x00007f58d52f28c8 dead>]

The command line may also contain arguments and options for the command:

    Open3.popen3('echo "Foo"') { |i, o, e, t| o.gets }
    "Foo\n"

Argument `exe_path`

Argument `exe_path` is one of the following:

- The string path to an executable to be called.

- A 2-element array containing the path to an executable and the string to be used as the name of the executing process.

Example:

    Open3.popen3('/usr/bin/date') { |i, o, e, t| o.gets }
    # => "Wed Sep 27 02:56:44 PM CDT 2023\n"

Ruby invokes the executable directly, with no shell and no shell expansion:

    Open3.popen3('doesnt_exist') { |i, o, e, t| o.gets } # Raises Errno::ENOENT

If one or more `args` is given, each is an argument or option to be passed to the executable:

    Open3.popen3('echo', 'C #') { |i, o, e, t| o.gets }
    # => "C #\n"
    Open3.popen3('echo', 'hello', 'world') { |i, o, e, t| o.gets }
    # => "hello world\n"

Take care to avoid deadlocks. Output streams `stdout` and `stderr` have fixed-size buffers, so reading extensively from one but not the other can cause a deadlock when the unread buffer fills. To avoid that, `stdout` and `stderr` should be read simultaneously (using threads or `IO.select`).

Related:

- `Open3.popen2`: Makes the standard input and standard output streams of the child process available as separate streams, with no access to the standard error stream.

- `Open3.popen2e`: Makes the standard input and the merge of the standard output and standard error streams of the child process available as separate streams.

### Private Instance Methods

capture2([env, ] command_line, options = {}) → [stdout_s, status]
capture2([env, ] exe_path, *args, options = {}) → [stdout_s, status]
Source

    # File lib/open3.rb, line 775
    def capture2(*cmd)
      if Hash === cmd.last
        opts = cmd.pop.dup
      else
        opts = {}
      end

      stdin_data = opts.delete(:stdin_data)
      binmode = opts.delete(:binmode)

      popen2(*cmd, opts) {|i, o, t|
        if binmode
          i.binmode
          o.binmode
        end
        out_reader = Thread.new { o.read }
        if stdin_data
          begin
            if stdin_data.respond_to? :readpartial
              IO.copy_stream(stdin_data, i)
            else
              i.write stdin_data
            end
          rescue Errno::EPIPE
          end
        end
        i.close
        [out_reader.value, t.value]
      }
    end

Basically a wrapper for `Open3.popen3` that:

- Creates a child process, by calling `Open3.popen3` with the given arguments (except for certain entries in hash `options`; see below).

- Returns as string `stdout_s` the standard output of the child process.

- Returns as `status` a `Process::Status` object that represents the exit status of the child process.

Returns the array `[stdout_s, status]`:

    stdout_s, status = Open3.capture2('echo "Foo"')
    # => ["Foo\n", #<Process::Status: pid 2326047 exit 0>]

Like `Process.spawn`, this method has potential security vulnerabilities if called with untrusted input; see Command Injection.

Unlike `Process.spawn`, this method waits for the child process to exit before returning, so the caller need not do so.

If the first argument is a hash, it becomes leading argument `env` in the call to `Open3.popen3`; see Execution Environment.

If the last argument is a hash, it becomes trailing argument `options` in the call to `Open3.popen3`; see Execution Options.

The hash `options` is given; two options have local effect in method `Open3.capture2`:

- If entry `options[:stdin_data]` exists, the entry is removed and its string value is sent to the command’s standard input:

      Open3.capture2('tee', stdin_data: 'Foo')

      # => ["Foo", #<Process::Status: pid 2326087 exit 0>]

- If entry `options[:binmode]` exists, the entry is removed and the internal streams are set to binary mode.

The single required argument is one of the following:

- `command_line` if it is a string, and if it begins with a shell reserved word or special built-in, or if it contains one or more metacharacters.

- `exe_path` otherwise.

Argument `command_line`

String argument `command_line` is a command line to be passed to a shell; it must begin with a shell reserved word, begin with a special built-in, or contain meta characters:

    Open3.capture2('if true; then echo "Foo"; fi') # Shell reserved word.
    # => ["Foo\n", #<Process::Status: pid 2326131 exit 0>]
    Open3.capture2('echo')                         # Built-in.
    # => ["\n", #<Process::Status: pid 2326139 exit 0>]
    Open3.capture2('date > date.tmp')              # Contains meta character.
    # => ["", #<Process::Status: pid 2326174 exit 0>]

The command line may also contain arguments and options for the command:

    Open3.capture2('echo "Foo"')
    # => ["Foo\n", #<Process::Status: pid 2326183 exit 0>]

Argument `exe_path`

Argument `exe_path` is one of the following:

- The string path to an executable to be called.

- A 2-element array containing the path to an executable and the string to be used as the name of the executing process.

Example:

    Open3.capture2('/usr/bin/date')
    # => ["Fri Sep 29 01:00:39 PM CDT 2023\n", #<Process::Status: pid 2326222 exit 0>]

Ruby invokes the executable directly, with no shell and no shell expansion:

    Open3.capture2('doesnt_exist') # Raises Errno::ENOENT

If one or more `args` is given, each is an argument or option to be passed to the executable:

    Open3.capture2('echo', 'C #')
    # => ["C #\n", #<Process::Status: pid 2326267 exit 0>]
    Open3.capture2('echo', 'hello', 'world')
    # => ["hello world\n", #<Process::Status: pid 2326299 exit 0>]

capture2e([env, ] command_line, options = {}) → [stdout_and_stderr_s, status]
capture2e([env, ] exe_path, *args, options = {}) → [stdout_and_stderr_s, status]
Source

    # File lib/open3.rb, line 902
    def capture2e(*cmd)
      if Hash === cmd.last
        opts = cmd.pop.dup
      else
        opts = {}
      end

      stdin_data = opts.delete(:stdin_data)
      binmode = opts.delete(:binmode)

      popen2e(*cmd, opts) {|i, oe, t|
        if binmode
          i.binmode
          oe.binmode
        end
        outerr_reader = Thread.new { oe.read }
        if stdin_data
          begin
            if stdin_data.respond_to? :readpartial
              IO.copy_stream(stdin_data, i)
            else
              i.write stdin_data
            end
          rescue Errno::EPIPE
          end
        end
        i.close
        [outerr_reader.value, t.value]
      }
    end

Basically a wrapper for `Open3.popen3` that:

- Creates a child process, by calling `Open3.popen3` with the given arguments (except for certain entries in hash `options`; see below).

- Returns as string `stdout_and_stderr_s` the merged standard output and standard error of the child process.

- Returns as `status` a `Process::Status` object that represents the exit status of the child process.

Returns the array `[stdout_and_stderr_s, status]`:

    stdout_and_stderr_s, status = Open3.capture2e('echo "Foo"')
    # => ["Foo\n", #<Process::Status: pid 2371692 exit 0>]

Like `Process.spawn`, this method has potential security vulnerabilities if called with untrusted input; see Command Injection.

Unlike `Process.spawn`, this method waits for the child process to exit before returning, so the caller need not do so.

If the first argument is a hash, it becomes leading argument `env` in the call to `Open3.popen3`; see Execution Environment.

If the last argument is a hash, it becomes trailing argument `options` in the call to `Open3.popen3`; see Execution Options.

The hash `options` is given; two options have local effect in method `Open3.capture2e`:

- If entry `options[:stdin_data]` exists, the entry is removed and its string value is sent to the command’s standard input:

      Open3.capture2e('tee', stdin_data: 'Foo')
      # => ["Foo", #<Process::Status: pid 2371732 exit 0>]

- If entry `options[:binmode]` exists, the entry is removed and the internal streams are set to binary mode.

The single required argument is one of the following:

- `command_line` if it is a string, and if it begins with a shell reserved word or special built-in, or if it contains one or more metacharacters.

- `exe_path` otherwise.

Argument `command_line`

String argument `command_line` is a command line to be passed to a shell; it must begin with a shell reserved word, begin with a special built-in, or contain meta characters:

    Open3.capture2e('if true; then echo "Foo"; fi') # Shell reserved word.
    # => ["Foo\n", #<Process::Status: pid 2371740 exit 0>]
    Open3.capture2e('echo')                         # Built-in.
    # => ["\n", #<Process::Status: pid 2371774 exit 0>]
    Open3.capture2e('date > date.tmp')              # Contains meta character.
    # => ["", #<Process::Status: pid 2371812 exit 0>]

The command line may also contain arguments and options for the command:

    Open3.capture2e('echo "Foo"')
    # => ["Foo\n", #<Process::Status: pid 2326183 exit 0>]

Argument `exe_path`

Argument `exe_path` is one of the following:

- The string path to an executable to be called.

- A 2-element array containing the path to an executable and the string to be used as the name of the executing process.

Example:

    Open3.capture2e('/usr/bin/date')
    # => ["Sat Sep 30 09:01:46 AM CDT 2023\n", #<Process::Status: pid 2371820 exit 0>]

Ruby invokes the executable directly, with no shell and no shell expansion:

    Open3.capture2e('doesnt_exist') # Raises Errno::ENOENT

If one or more `args` is given, each is an argument or option to be passed to the executable:

    Open3.capture2e('echo', 'C #')
    # => ["C #\n", #<Process::Status: pid 2371856 exit 0>]
    Open3.capture2e('echo', 'hello', 'world')
    # => ["hello world\n", #<Process::Status: pid 2371894 exit 0>]

capture3([env, ] command_line, options = {}) → [stdout_s, stderr_s, status]
capture3([env, ] exe_path, *args, options = {}) → [stdout_s, stderr_s, status]
Source

    # File lib/open3.rb, line 648
    def capture3(*cmd)
      if Hash === cmd.last
        opts = cmd.pop.dup
      else
        opts = {}
      end

      stdin_data = opts.delete(:stdin_data) || ''
      binmode = opts.delete(:binmode)

      popen3(*cmd, opts) {|i, o, e, t|
        if binmode
          i.binmode
          o.binmode
          e.binmode
        end
        out_reader = Thread.new { o.read }
        err_reader = Thread.new { e.read }
        begin
          if stdin_data.respond_to? :readpartial
            IO.copy_stream(stdin_data, i)
          else
            i.write stdin_data
          end
        rescue Errno::EPIPE
        end
        i.close
        [out_reader.value, err_reader.value, t.value]
      }
    end

Basically a wrapper for `Open3.popen3` that:

- Creates a child process, by calling `Open3.popen3` with the given arguments (except for certain entries in hash `options`; see below).

- Returns as strings `stdout_s` and `stderr_s` the standard output and standard error of the child process.

- Returns as `status` a `Process::Status` object that represents the exit status of the child process.

Returns the array `[stdout_s, stderr_s, status]`:

    stdout_s, stderr_s, status = Open3.capture3('echo "Foo"')
    # => ["Foo\n", "", #<Process::Status: pid 2281954 exit 0>]

Like `Process.spawn`, this method has potential security vulnerabilities if called with untrusted input; see Command Injection.

Unlike `Process.spawn`, this method waits for the child process to exit before returning, so the caller need not do so.

If the first argument is a hash, it becomes leading argument `env` in the call to `Open3.popen3`; see Execution Environment.

If the last argument is a hash, it becomes trailing argument `options` in the call to `Open3.popen3`; see Execution Options.

The hash `options` is given; two options have local effect in method `Open3.capture3`:

- If entry `options[:stdin_data]` exists, the entry is removed and its string value is sent to the command’s standard input:

      Open3.capture3('tee', stdin_data: 'Foo')
      # => ["Foo", "", #<Process::Status: pid 2319575 exit 0>]

- If entry `options[:binmode]` exists, the entry is removed and the internal streams are set to binary mode.

The single required argument is one of the following:

- `command_line` if it is a string, and if it begins with a shell reserved word or special built-in, or if it contains one or more metacharacters.

- `exe_path` otherwise.

Argument `command_line`

String argument `command_line` is a command line to be passed to a shell; it must begin with a shell reserved word, begin with a special built-in, or contain meta characters:

    Open3.capture3('if true; then echo "Foo"; fi') # Shell reserved word.
    # => ["Foo\n", "", #<Process::Status: pid 2282025 exit 0>]
    Open3.capture3('echo')                         # Built-in.
    # => ["\n", "", #<Process::Status: pid 2282092 exit 0>]
    Open3.capture3('date > date.tmp')              # Contains meta character.
    # => ["", "", #<Process::Status: pid 2282110 exit 0>]

The command line may also contain arguments and options for the command:

    Open3.capture3('echo "Foo"')
    # => ["Foo\n", "", #<Process::Status: pid 2282092 exit 0>]

Argument `exe_path`

Argument `exe_path` is one of the following:

- The string path to an executable to be called.

- A 2-element array containing the path to an executable and the string to be used as the name of the executing process.

Example:

    Open3.capture3('/usr/bin/date')
    # => ["Thu Sep 28 05:03:51 PM CDT 2023\n", "", #<Process::Status: pid 2282300 exit 0>]

Ruby invokes the executable directly, with no shell and no shell expansion:

    Open3.capture3('doesnt_exist') # Raises Errno::ENOENT

If one or more `args` is given, each is an argument or option to be passed to the executable:

    Open3.capture3('echo', 'C #')
    # => ["C #\n", "", #<Process::Status: pid 2282368 exit 0>]
    Open3.capture3('echo', 'hello', 'world')
    # => ["hello world\n", "", #<Process::Status: pid 2282372 exit 0>]

pipeline([env, ] *cmds, options = {}) → array_of_statuses
Source

    # File lib/open3.rb, line 1334
    def pipeline(*cmds)
      if Hash === cmds.last
        opts = cmds.pop.dup
      else
        opts = {}
      end

      pipeline_run(cmds, opts, [], []) {|ts|
        ts.map(&:value)
      }
    end

Basically a wrapper for `Process.spawn` that:

- Creates a child process for each of the given `cmds` by calling `Process.spawn`.

- Pipes the `stdout` from each child to the `stdin` of the next child, or, for the last child, to the caller’s `stdout`.

- Waits for the child processes to exit.

- Returns an array of `Process::Status` objects (one for each child).

Example:

    wait_threads = Open3.pipeline('ls', 'grep R')
    # => [#<Process::Status: pid 2139200 exit 0>, #<Process::Status: pid 2139202 exit 0>]

Output:

    Rakefile
    README.md

Like `Process.spawn`, this method has potential security vulnerabilities if called with untrusted input; see Command Injection.

If the first argument is a hash, it becomes leading argument `env` in each call to `Process.spawn`; see Execution Environment.

If the last argument is a hash, it becomes trailing argument `options` in each call to `Process.spawn`‘ see Execution Options.

Each remaining argument in `cmds` is one of:

- A `command_line`: a string that begins with a shell reserved word or special built-in, or contains one or more metacharacters.

- An `exe_path`: the string path to an executable to be called.

- An array containing a `command_line` or an `exe_path`, along with zero or more string arguments for the command.

See Argument command_line or exe_path.

pipeline_r([env, ] *cmds, options = {}) → [last_stdout, wait_threads]
Source

    # File lib/open3.rb, line 1104
    def pipeline_r(*cmds, &block)
      if Hash === cmds.last
        opts = cmds.pop.dup
      else
        opts = {}
      end

      out_r, out_w = IO.pipe
      opts[:out] = out_w

      pipeline_run(cmds, opts, [out_w], [out_r], &block)
    end

Basically a wrapper for `Process.spawn` that:

- Creates a child process for each of the given `cmds` by calling `Process.spawn`.

- Pipes the `stdout` from each child to the `stdin` of the next child, or, for the last child, to the caller’s `stdout`.

The method does not wait for child processes to exit, so the caller must do so.

With no block given, returns a 2-element array containing:

- The `stdout` stream of the last child process.

- An array of the wait threads for all of the child processes.

Example:

    last_stdout, wait_threads = Open3.pipeline_r('ls', 'grep R')
    # => [#<IO:fd 5>, [#<Process::Waiter:0x000055e8de2f9898 dead>, #<Process::Waiter:0x000055e8de2f94b0 sleep>]]
    puts last_stdout.read
    wait_threads.each do |wait_thread|
      wait_thread.join
    end

Output:

    Rakefile
    README.md

With a block given, calls the block with the `stdout` stream of the last child process, and an array of the wait processes:

    Open3.pipeline_r('ls', 'grep R') do |last_stdout, wait_threads|
      puts last_stdout.read
      wait_threads.each do |wait_thread|
        wait_thread.join
      end
    end

Output:

    Rakefile
    README.md

Like `Process.spawn`, this method has potential security vulnerabilities if called with untrusted input; see Command Injection.

If the first argument is a hash, it becomes leading argument `env` in each call to `Process.spawn`; see Execution Environment.

If the last argument is a hash, it becomes trailing argument `options` in each call to `Process.spawn`; see Execution Options.

Each remaining argument in `cmds` is one of:

- A `command_line`: a string that begins with a shell reserved word or special built-in, or contains one or more metacharacters.

- An `exe_path`: the string path to an executable to be called.

- An array containing a `command_line` or an `exe_path`, along with zero or more string arguments for the command.

See Argument command_line or exe_path.

pipeline_rw([env, ] *cmds, options = {}) → [first_stdin, last_stdout, wait_threads]
Source

    # File lib/open3.rb, line 1014
    def pipeline_rw(*cmds, &block)
      if Hash === cmds.last
        opts = cmds.pop.dup
      else
        opts = {}
      end

      in_r, in_w = IO.pipe
      opts[:in] = in_r
      in_w.sync = true

      out_r, out_w = IO.pipe
      opts[:out] = out_w

      pipeline_run(cmds, opts, [in_r, out_w], [in_w, out_r], &block)
    end

Basically a wrapper for `Process.spawn` that:

- Creates a child process for each of the given `cmds` by calling `Process.spawn`.

- Pipes the `stdout` from each child to the `stdin` of the next child, or, for the first child, from the caller’s `stdin`, or, for the last child, to the caller’s `stdout`.

The method does not wait for child processes to exit, so the caller must do so.

With no block given, returns a 3-element array containing:

- The `stdin` stream of the first child process.

- The `stdout` stream of the last child process.

- An array of the wait threads for all of the child processes.

Example:

    first_stdin, last_stdout, wait_threads = Open3.pipeline_rw('sort', 'cat -n')
    # => [#<IO:fd 20>, #<IO:fd 21>, [#<Process::Waiter:0x000055e8de29ab40 sleep>, #<Process::Waiter:0x000055e8de29a690 sleep>]]
    first_stdin.puts("foo\nbar\nbaz")
    first_stdin.close # Send EOF to sort.
    puts last_stdout.read
    wait_threads.each do |wait_thread|
      wait_thread.join
    end

Output:

    1 bar
    2 baz
    3 foo

With a block given, calls the block with the `stdin` stream of the first child, the `stdout` stream of the last child, and an array of the wait processes:

    Open3.pipeline_rw('sort', 'cat -n') do |first_stdin, last_stdout, wait_threads|
      first_stdin.puts "foo\nbar\nbaz"
      first_stdin.close # send EOF to sort.
      puts last_stdout.read
      wait_threads.each do |wait_thread|
        wait_thread.join
      end
    end

Output:

    1 bar
    2 baz
    3 foo

Like `Process.spawn`, this method has potential security vulnerabilities if called with untrusted input; see Command Injection.

If the first argument is a hash, it becomes leading argument `env` in each call to `Process.spawn`; see Execution Environment.

If the last argument is a hash, it becomes trailing argument `options` in each call to `Process.spawn`; see Execution Options.

Each remaining argument in `cmds` is one of:

- A `command_line`: a string that begins with a shell reserved word or special built-in, or contains one or more metacharacters.

- An `exe_path`: the string path to an executable to be called.

- An array containing a `command_line` or an `exe_path`, along with zero or more string arguments for the command.

See Argument command_line or exe_path.

pipeline_start([env, ] *cmds, options = {}) → [wait_threads]
Source

    # File lib/open3.rb, line 1272
    def pipeline_start(*cmds, &block)
      if Hash === cmds.last
        opts = cmds.pop.dup
      else
        opts = {}
      end

      if block
        pipeline_run(cmds, opts, [], [], &block)
      else
        ts, = pipeline_run(cmds, opts, [], [])
        ts
      end
    end

Basically a wrapper for `Process.spawn` that:

- Creates a child process for each of the given `cmds` by calling `Process.spawn`.

- Does not wait for child processes to exit.

With no block given, returns an array of the wait threads for all of the child processes.

Example:

    wait_threads = Open3.pipeline_start('ls', 'grep R')
    # => [#<Process::Waiter:0x000055e8de9d2bb0 run>, #<Process::Waiter:0x000055e8de9d2890 run>]
    wait_threads.each do |wait_thread|
      wait_thread.join
    end

Output:

    Rakefile
    README.md

With a block given, calls the block with an array of the wait processes:

    Open3.pipeline_start('ls', 'grep R') do |wait_threads|
      wait_threads.each do |wait_thread|
        wait_thread.join
      end
    end

Output:

    Rakefile
    README.md

Like `Process.spawn`, this method has potential security vulnerabilities if called with untrusted input; see Command Injection.

If the first argument is a hash, it becomes leading argument `env` in each call to `Process.spawn`; see Execution Environment.

If the last argument is a hash, it becomes trailing argument `options` in each call to `Process.spawn`; see Execution Options.

Each remaining argument in `cmds` is one of:

- A `command_line`: a string that begins with a shell reserved word or special built-in, or contains one or more metacharacters.

- An `exe_path`: the string path to an executable to be called.

- An array containing a `command_line` or an `exe_path`, along with zero or more string arguments for the command.

See Argument command_line or exe_path.

pipeline_w([env, ] *cmds, options = {}) → [first_stdin, wait_threads]
Source

    # File lib/open3.rb, line 1195
    def pipeline_w(*cmds, &block)
      if Hash === cmds.last
        opts = cmds.pop.dup
      else
        opts = {}
      end

      in_r, in_w = IO.pipe
      opts[:in] = in_r
      in_w.sync = true

      pipeline_run(cmds, opts, [in_r], [in_w], &block)
    end

Basically a wrapper for `Process.spawn` that:

- Creates a child process for each of the given `cmds` by calling `Process.spawn`.

- Pipes the `stdout` from each child to the `stdin` of the next child, or, for the first child, pipes the caller’s `stdout` to the child’s `stdin`.

The method does not wait for child processes to exit, so the caller must do so.

With no block given, returns a 2-element array containing:

- The `stdin` stream of the first child process.

- An array of the wait threads for all of the child processes.

Example:

    first_stdin, wait_threads = Open3.pipeline_w('sort', 'cat -n')
    # => [#<IO:fd 7>, [#<Process::Waiter:0x000055e8de928278 run>, #<Process::Waiter:0x000055e8de923e80 run>]]
    first_stdin.puts("foo\nbar\nbaz")
    first_stdin.close # Send EOF to sort.
    wait_threads.each do |wait_thread|
      wait_thread.join
    end

Output:

    1 bar
    2 baz
    3 foo

With a block given, calls the block with the `stdin` stream of the first child process, and an array of the wait processes:

    Open3.pipeline_w('sort', 'cat -n') do |first_stdin, wait_threads|
      first_stdin.puts("foo\nbar\nbaz")
      first_stdin.close # Send EOF to sort.
      wait_threads.each do |wait_thread|
        wait_thread.join
      end
    end

Output:

    1 bar
    2 baz
    3 foo

Like `Process.spawn`, this method has potential security vulnerabilities if called with untrusted input; see Command Injection.

If the first argument is a hash, it becomes leading argument `env` in each call to `Process.spawn`; see Execution Environment.

If the last argument is a hash, it becomes trailing argument `options` in each call to `Process.spawn`; see Execution Options.

Each remaining argument in `cmds` is one of:

- A `command_line`: a string that begins with a shell reserved word or special built-in, or contains one or more metacharacters.

- An `exe_path`: the string path to an executable to be called.

- An array containing a `command_line` or an `exe_path`, along with zero or more string arguments for the command.

See Argument command_line or exe_path.

popen2([env, ] command_line, options = {}) → [stdin, stdout, wait_thread]
popen2([env, ] exe_path, *args, options = {}) → [stdin, stdout, wait_thread]
popen2([env, ] command_line, options = {}) {|stdin, stdout, wait_thread| ... } → object
popen2([env, ] exe_path, *args, options = {}) {|stdin, stdout, wait_thread| ... } → object
Source

    # File lib/open3.rb, line 365
    def popen2(*cmd, &block)
      if Hash === cmd.last
        opts = cmd.pop.dup
      else
        opts = {}
      end

      in_r, in_w = IO.pipe
      opts[:in] = in_r
      in_w.sync = true

      out_r, out_w = IO.pipe
      opts[:out] = out_w

      popen_run(cmd, opts, [in_r, out_w], [in_w, out_r], &block)
    end

Basically a wrapper for `Process.spawn` that:

- Creates a child process, by calling `Process.spawn` with the given arguments.

- Creates streams `stdin` and `stdout`, which are the standard input and standard output streams in the child process.

- Creates thread `wait_thread` that waits for the child process to exit; the thread has method `pid`, which returns the process ID of the child process.

With no block given, returns the array `[stdin, stdout, wait_thread]`. The caller should close each of the two returned streams.

    stdin, stdout, wait_thread = Open3.popen2('echo')
    # => [#<IO:fd 6>, #<IO:fd 7>, #<Process::Waiter:0x00007f58d52dbe98 run>]
    stdin.close
    stdout.close
    wait_thread.pid   # => 2263572
    wait_thread.value # => #<Process::Status: pid 2263572 exit 0>

With a block given, calls the block with the three variables (two streams and the wait thread) and returns the block’s return value. The caller need not close the streams:

    Open3.popen2('echo') do |stdin, stdout, wait_thread|
      p stdin
      p stdout
      p wait_thread
      p wait_thread.pid
      p wait_thread.value
    end

Output:

    #<IO:fd 6>
    #<IO:fd 7>
    #<Process::Waiter:0x00007f58d59a34b0 sleep>
    2263636
    #<Process::Status: pid 2263636 exit 0>

Like `Process.spawn`, this method has potential security vulnerabilities if called with untrusted input; see Command Injection.

Unlike `Process.spawn`, this method waits for the child process to exit before returning, so the caller need not do so.

If the first argument is a hash, it becomes leading argument `env` in the call to `Process.spawn`; see Execution Environment.

If the last argument is a hash, it becomes trailing argument `options` in the call to `Process.spawn`; see Execution Options.

The single required argument is one of the following:

- `command_line` if it is a string, and if it begins with a shell reserved word or special built-in, or if it contains one or more metacharacters.

- `exe_path` otherwise.

Argument `command_line`

String argument `command_line` is a command line to be passed to a shell; it must begin with a shell reserved word, begin with a special built-in, or contain meta characters:

    Open3.popen2('if true; then echo "Foo"; fi') {|*args| p args } # Shell reserved word.
    Open3.popen2('echo') {|*args| p args }                         # Built-in.
    Open3.popen2('date > date.tmp') {|*args| p args }              # Contains meta character.

Output (similar for each call above):

    # => [#<IO:(closed)>, #<IO:(closed)>, #<Process::Waiter:0x00007f7577dfe410 dead>]

The command line may also contain arguments and options for the command:

    Open3.popen2('echo "Foo"') { |i, o, t| o.gets }
    "Foo\n"

Argument `exe_path`

Argument `exe_path` is one of the following:

- The string path to an executable to be called.

- A 2-element array containing the path to an executable and the string to be used as the name of the executing process.

Example:

    Open3.popen2('/usr/bin/date') { |i, o, t| o.gets }
    # => "Thu Sep 28 09:41:06 AM CDT 2023\n"

Ruby invokes the executable directly, with no shell and no shell expansion:

    Open3.popen2('doesnt_exist') { |i, o, t| o.gets } # Raises Errno::ENOENT

If one or more `args` is given, each is an argument or option to be passed to the executable:

    Open3.popen2('echo', 'C #') { |i, o, t| o.gets }
    # => "C #\n"
    Open3.popen2('echo', 'hello', 'world') { |i, o, t| o.gets }
    # => "hello world\n"

Related:

- `Open3.popen2e`: Makes the standard input and the merge of the standard output and standard error streams of the child process available as separate streams.

- `Open3.popen3`: Makes the standard input, standard output, and standard error streams of the child process available as separate streams.

popen2e([env, ] command_line, options = {}) → [stdin, stdout_and_stderr, wait_thread]
popen2e([env, ] exe_path, *args, options = {}) → [stdin, stdout_and_stderr, wait_thread]
popen2e([env, ] command_line, options = {}) {|stdin, stdout_and_stderr, wait_thread| ... } → object
popen2e([env, ] exe_path, *args, options = {}) {|stdin, stdout_and_stderr, wait_thread| ... } → object
Source

    # File lib/open3.rb, line 508
    def popen2e(*cmd, &block)
      if Hash === cmd.last
        opts = cmd.pop.dup
      else
        opts = {}
      end

      in_r, in_w = IO.pipe
      opts[:in] = in_r
      in_w.sync = true

      out_r, out_w = IO.pipe
      opts[[:out, :err]] = out_w

      popen_run(cmd, opts, [in_r, out_w], [in_w, out_r], &block)
    ensure
      if block
        in_r.close
        in_w.close
        out_r.close
        out_w.close
      end
    end

Basically a wrapper for `Process.spawn` that:

- Creates a child process, by calling `Process.spawn` with the given arguments.

- Creates streams `stdin`, `stdout_and_stderr`, which are the standard input and the merge of the standard output and standard error streams in the child process.

- Creates thread `wait_thread` that waits for the child process to exit; the thread has method `pid`, which returns the process ID of the child process.

With no block given, returns the array `[stdin, stdout_and_stderr, wait_thread]`. The caller should close each of the two returned streams.

    stdin, stdout_and_stderr, wait_thread = Open3.popen2e('echo')
    # => [#<IO:fd 6>, #<IO:fd 7>, #<Process::Waiter:0x00007f7577da4398 run>]
    stdin.close
    stdout_and_stderr.close
    wait_thread.pid   # => 2274600
    wait_thread.value # => #<Process::Status: pid 2274600 exit 0>

With a block given, calls the block with the three variables (two streams and the wait thread) and returns the block’s return value. The caller need not close the streams:

    Open3.popen2e('echo') do |stdin, stdout_and_stderr, wait_thread|
      p stdin
      p stdout_and_stderr
      p wait_thread
      p wait_thread.pid
      p wait_thread.value
    end

Output:

    #<IO:fd 6>
    #<IO:fd 7>
    #<Process::Waiter:0x00007f75777578c8 sleep>
    2274763
    #<Process::Status: pid 2274763 exit 0>

Like `Process.spawn`, this method has potential security vulnerabilities if called with untrusted input; see Command Injection.

Unlike `Process.spawn`, this method waits for the child process to exit before returning, so the caller need not do so.

If the first argument is a hash, it becomes leading argument `env` in the call to `Process.spawn`; see Execution Environment.

If the last argument is a hash, it becomes trailing argument `options` in the call to `Process.spawn`; see Execution Options.

The single required argument is one of the following:

- `command_line` if it is a string, and if it begins with a shell reserved word or special built-in, or if it contains one or more metacharacters.

- `exe_path` otherwise.

Argument `command_line`

String argument `command_line` is a command line to be passed to a shell; it must begin with a shell reserved word, begin with a special built-in, or contain meta characters:

    Open3.popen2e('if true; then echo "Foo"; fi') {|*args| p args } # Shell reserved word.
    Open3.popen2e('echo') {|*args| p args }                         # Built-in.
    Open3.popen2e('date > date.tmp') {|*args| p args }              # Contains meta character.

Output (similar for each call above):

    # => [#<IO:(closed)>, #<IO:(closed)>, #<Process::Waiter:0x00007f7577d8a1f0 dead>]

The command line may also contain arguments and options for the command:

    Open3.popen2e('echo "Foo"') { |i, o_and_e, t| o_and_e.gets }
    "Foo\n"

Argument `exe_path`

Argument `exe_path` is one of the following:

- The string path to an executable to be called.

- A 2-element array containing the path to an executable and the string to be used as the name of the executing process.

Example:

    Open3.popen2e('/usr/bin/date') { |i, o_and_e, t| o_and_e.gets }
    # => "Thu Sep 28 01:58:45 PM CDT 2023\n"

Ruby invokes the executable directly, with no shell and no shell expansion:

    Open3.popen2e('doesnt_exist') { |i, o_and_e, t| o_and_e.gets } # Raises Errno::ENOENT

If one or more `args` is given, each is an argument or option to be passed to the executable:

    Open3.popen2e('echo', 'C #') { |i, o_and_e, t| o_and_e.gets }
    # => "C #\n"
    Open3.popen2e('echo', 'hello', 'world') { |i, o_and_e, t| o_and_e.gets }
    # => "hello world\n"

Related:

- `Open3.popen2`: Makes the standard input and standard output streams of the child process available as separate streams, with no access to the standard error stream.

- `Open3.popen3`: Makes the standard input, standard output, and standard error streams of the child process available as separate streams.

popen3([env, ] command_line, options = {}) → [stdin, stdout, stderr, wait_thread]
popen3([env, ] exe_path, *args, options = {}) → [stdin, stdout, stderr, wait_thread]
popen3([env, ] command_line, options = {}) {|stdin, stdout, stderr, wait_thread| ... } → object
popen3([env, ] exe_path, *args, options = {}) {|stdin, stdout, stderr, wait_thread| ... } → object
Source

    # File lib/open3.rb, line 218
    def popen3(*cmd, &block)
      if Hash === cmd.last
        opts = cmd.pop.dup
      else
        opts = {}
      end

      in_r, in_w = IO.pipe
      opts[:in] = in_r
      in_w.sync = true

      out_r, out_w = IO.pipe
      opts[:out] = out_w

      err_r, err_w = IO.pipe
      opts[:err] = err_w

      popen_run(cmd, opts, [in_r, out_w, err_w], [in_w, out_r, err_r], &block)
    end

Basically a wrapper for `Process.spawn` that:

- Creates a child process, by calling `Process.spawn` with the given arguments.

- Creates streams `stdin`, `stdout`, and `stderr`, which are the standard input, standard output, and standard error streams in the child process.

- Creates thread `wait_thread` that waits for the child process to exit; the thread has method `pid`, which returns the process ID of the child process.

With no block given, returns the array `[stdin, stdout, stderr, wait_thread]`. The caller should close each of the three returned streams.

    stdin, stdout, stderr, wait_thread = Open3.popen3('echo')
    # => [#<IO:fd 8>, #<IO:fd 10>, #<IO:fd 12>, #<Process::Waiter:0x00007f58d5428f58 run>]
    stdin.close
    stdout.close
    stderr.close
    wait_thread.pid   # => 2210481
    wait_thread.value # => #<Process::Status: pid 2210481 exit 0>

With a block given, calls the block with the four variables (three streams and the wait thread) and returns the block’s return value. The caller need not close the streams:

    Open3.popen3('echo') do |stdin, stdout, stderr, wait_thread|
      p stdin
      p stdout
      p stderr
      p wait_thread
      p wait_thread.pid
      p wait_thread.value
    end

Output:

    #<IO:fd 6>
    #<IO:fd 7>
    #<IO:fd 9>
    #<Process::Waiter:0x00007f58d53606e8 sleep>
    2211047
    #<Process::Status: pid 2211047 exit 0>

Like `Process.spawn`, this method has potential security vulnerabilities if called with untrusted input; see Command Injection.

Unlike `Process.spawn`, this method waits for the child process to exit before returning, so the caller need not do so.

If the first argument is a hash, it becomes leading argument `env` in the call to `Process.spawn`; see Execution Environment.

If the last argument is a hash, it becomes trailing argument `options` in the call to `Process.spawn`; see Execution Options.

The single required argument is one of the following:

- `command_line` if it is a string, and if it begins with a shell reserved word or special built-in, or if it contains one or more metacharacters.

- `exe_path` otherwise.

Argument `command_line`

String argument `command_line` is a command line to be passed to a shell; it must begin with a shell reserved word, begin with a special built-in, or contain meta characters:

    Open3.popen3('if true; then echo "Foo"; fi') {|*args| p args } # Shell reserved word.
    Open3.popen3('echo') {|*args| p args }                         # Built-in.
    Open3.popen3('date > date.tmp') {|*args| p args }              # Contains meta character.

Output (similar for each call above):

    [#<IO:(closed)>, #<IO:(closed)>, #<IO:(closed)>, #<Process::Waiter:0x00007f58d52f28c8 dead>]

The command line may also contain arguments and options for the command:

    Open3.popen3('echo "Foo"') { |i, o, e, t| o.gets }
    "Foo\n"

Argument `exe_path`

Argument `exe_path` is one of the following:

- The string path to an executable to be called.

- A 2-element array containing the path to an executable and the string to be used as the name of the executing process.

Example:

    Open3.popen3('/usr/bin/date') { |i, o, e, t| o.gets }
    # => "Wed Sep 27 02:56:44 PM CDT 2023\n"

Ruby invokes the executable directly, with no shell and no shell expansion:

    Open3.popen3('doesnt_exist') { |i, o, e, t| o.gets } # Raises Errno::ENOENT

If one or more `args` is given, each is an argument or option to be passed to the executable:

    Open3.popen3('echo', 'C #') { |i, o, e, t| o.gets }
    # => "C #\n"
    Open3.popen3('echo', 'hello', 'world') { |i, o, e, t| o.gets }
    # => "hello world\n"

Take care to avoid deadlocks. Output streams `stdout` and `stderr` have fixed-size buffers, so reading extensively from one but not the other can cause a deadlock when the unread buffer fills. To avoid that, `stdout` and `stderr` should be read simultaneously (using threads or `IO.select`).

Related:

- `Open3.popen2`: Makes the standard input and standard output streams of the child process available as separate streams, with no access to the standard error stream.

- `Open3.popen2e`: Makes the standard input and the merge of the standard output and standard error streams of the child process available as separate streams.