module Open3

# 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>]

# 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>]

# 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>]

# 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.

# 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.

# 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.

# 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.

# 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.

# 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.

# 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.

# 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.

# 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>]

# 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>]

# 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>]

# 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.

# 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.

# 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.

# 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.

# 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.

# 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.

# 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.

# 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.