Module: Open3

Defined in:
lib/open3.rb

Overview

Open3 grants you access to stdin, stdout, stderr and a thread to wait the child process when running another program. You can specify various attributes, redirections, current directory, etc., of the program as Process.spawn.

  • Open3.popen3 : pipes for stdin, stdout, stderr

  • Open3.popen2 : pipes for stdin, stdout

  • Open3.popen2e : pipes for stdin, merged stdout and stderr

  • Open3.capture3 : give a string for stdin. get strings for stdout, stderr

  • Open3.capture2 : give a string for stdin. get a string for stdout

  • Open3.capture2e : give a string for stdin. get a string for merged stdout and stderr

  • Open3.pipeline_rw : pipes for first stdin and last stdout of a pipeline

  • Open3.pipeline_r : pipe for last stdout of a pipeline

  • Open3.pipeline_w : pipe for first stdin of a pipeline

  • Open3.pipeline_start : run a pipeline and don't wait

  • Open3.pipeline : run a pipeline and wait

Class Method Summary collapse

Class Method Details

.capture2(*cmd) ⇒ Object

Open3.capture2 captures the standard output of a command.

stdout_str, status = Open3.capture2([env,] cmd... [, opts])

The arguments env, cmd and opts are passed to Open3.popen3 except opts and opts. See Process.spawn.

If opts is specified, it is sent to the command's standard input.

If opts is true, internal pipes are set to binary mode.

Example:

# factor is a command for integer factorization.
o, s = Open3.capture2("factor", :stdin_data=>"42")
p o #=> "42: 2 3 7\n"

# generate x**2 graph in png using gnuplot.
gnuplot_commands = <<"End"
  set terminal png
  plot x**2, "-" with lines
  1 14
  2 1
  3 8
  4 5
  e
End
image, s = Open3.capture2("gnuplot", :stdin_data=>gnuplot_commands, :binmode=>true)

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# File 'lib/open3.rb', line 323

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 }
    i.write stdin_data
    i.close
    [out_reader.value, t.value]
  }
end

.capture2e(*cmd) ⇒ Object

Open3.capture2e captures the standard output and the standard error of a command.

stdout_and_stderr_str, status = Open3.capture2e([env,] cmd... [, opts])

The arguments env, cmd and opts are passed to Open3.popen3 except opts and opts. See Process.spawn.

If opts is specified, it is sent to the command's standard input.

If opts is true, internal pipes are set to binary mode.

Example:

# capture make log
make_log, s = Open3.capture2e("make")

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# File 'lib/open3.rb', line 362

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 }
    i.write stdin_data
    i.close
    [outerr_reader.value, t.value]
  }
end

.capture3(*cmd) ⇒ Object

Open3.capture3 captures the standard output and the standard error of a command.

stdout_str, stderr_str, status = Open3.capture3([env,] cmd... [, opts])

The arguments env, cmd and opts are passed to Open3.popen3 except opts and opts. See Process.spawn.

If opts is specified, it is sent to the command's standard input.

If opts is true, internal pipes are set to binary mode.

Example:

# dot is a command of graphviz.
graph = <<'End'
  digraph g {
    a -> b
  }
End
layouted_graph, dot_log = Open3.capture3("dot -v", :stdin_data=>graph)

o, e, s = Open3.capture3("echo abc; sort >&2", :stdin_data=>"foo\nbar\nbaz\n")
p o #=> "abc\n"
p e #=> "bar\nbaz\nfoo\n"
p s #=> #<Process::Status: pid 32682 exit 0>

# generate a thumnail image using the convert command of ImageMagick.
# However, if the image stored really in a file,
# system("convert", "-thumbnail", "80", "png:#{filename}", "png:-") is better
# because memory consumption.
# But if the image is stored in a DB or generated by gnuplot Open3.capture2 example,
# Open3.capture3 is considerable.
#
image = File.read("/usr/share/openclipart/png/animals/mammals/sheep-md-v0.1.png", :binmode=>true)
thumnail, err, s = Open3.capture3("convert -thumbnail 80 png:- png:-", :stdin_data=>image, :binmode=>true)
if s.success?
  STDOUT.binmode; print thumnail
end

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# File 'lib/open3.rb', line 269

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 }
    i.write stdin_data
    i.close
    [out_reader.value, err_reader.value, t.value]
  }
end

.pipeline(*cmds) ⇒ Object

Open3.pipeline starts a list of commands as a pipeline. It waits the finish of the commands. No pipe made for stdin of the first command and stdout of the last command.

status_list = Open3.pipeline(cmd1, cmd2, ... [, opts])

Each cmd is a string or an array. If it is an array, the elements are passed to Process.spawn.

cmd:
  commandline                              command line string which is passed to a shell
  [env, commandline, opts]                 command line string which is passed to a shell
  [env, cmdname, arg1, ..., opts]          command name and one or more arguments (no shell)
  [env, [cmdname, argv0], arg1, ..., opts] command name and arguments including argv[0] (no shell)

Note that env and opts are optional, as Process.spawn.

Example:

fname = "/usr/share/man/man1/ruby.1.gz"
p Open3.pipeline(["zcat", fname], "nroff -man", "less")
#=> [#<Process::Status: pid 11817 exit 0>,
#    #<Process::Status: pid 11820 exit 0>,
#    #<Process::Status: pid 11828 exit 0>]

fname = "/usr/share/man/man1/ls.1.gz"
Open3.pipeline(["zcat", fname], "nroff -man", "colcrt")

# convert PDF to PS and send to a printer by lpr
pdf_file = "paper.pdf"
printer = "printer-name"
Open3.pipeline(["pdftops", pdf_file, "-"],
               ["lpr", "-P#{printer}"])

# count lines
Open3.pipeline("sort", "uniq -c", :in=>"names.txt", :out=>"count")

# cyclic pipeline
r,w = IO.pipe
w.print "ibase=14\n10\n"
Open3.pipeline("bc", "tee /dev/tty", :in=>r, :out=>w)
#=> 14
#   18
#   22
#   30
#   42
#   58
#   78
#   106
#   202

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# File 'lib/open3.rb', line 652

def pipeline(*cmds)
  if Hash === cmds.last
    opts = cmds.pop.dup
  else
    opts = {}
  end

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

.pipeline_r(*cmds, &block) ⇒ Object

Open3.pipeline_r starts a list of commands as a pipeline with a pipe which connects stdout of the last command.

Open3.pipeline_r(cmd1, cmd2, ... [, opts]) {|last_stdout, wait_threads|
  ...
}

last_stdout, wait_threads = Open3.pipeline_r(cmd1, cmd2, ... [, opts])
...
last_stdout.close

Each cmd is a string or an array. If it is an array, the elements are passed to Process.spawn.

cmd:
  commandline                              command line string which is passed to a shell
  [env, commandline, opts]                 command line string which is passed to a shell
  [env, cmdname, arg1, ..., opts]          command name and one or more arguments (no shell)
  [env, [cmdname, argv0], arg1, ..., opts] command name and arguments including argv[0] (no shell)

Note that env and opts are optional, as Process.spawn.

Example:

Open3.pipeline_r("zcat /var/log/apache2/access.log.*.gz",
                 [{"LANG"=>"C"}, "grep", "GET /favicon.ico"],
                 "logresolve") {|o, ts|
  o.each_line {|line|
    ...
  }
}

Open3.pipeline_r("yes", "head -10") {|o, ts|
  p o.read      #=> "y\ny\ny\ny\ny\ny\ny\ny\ny\ny\n"
  p ts[0].value #=> #<Process::Status: pid 24910 SIGPIPE (signal 13)>
  p ts[1].value #=> #<Process::Status: pid 24913 exit 0>
}

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# File 'lib/open3.rb', line 483

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

.pipeline_rw(*cmds, &block) ⇒ Object

Open3.pipeline_rw starts a list of commands as a pipeline with pipes which connects stdin of the first command and stdout of the last command.

Open3.pipeline_rw(cmd1, cmd2, ... [, opts]) {|first_stdin, last_stdout, wait_threads|
  ...
}

first_stdin, last_stdout, wait_threads = Open3.pipeline_rw(cmd1, cmd2, ... [, opts])
...
first_stdin.close
last_stdout.close

Each cmd is a string or an array. If it is an array, the elements are passed to Process.spawn.

cmd:
  commandline                              command line string which is passed to a shell
  [env, commandline, opts]                 command line string which is passed to a shell
  [env, cmdname, arg1, ..., opts]          command name and one or more arguments (no shell)
  [env, [cmdname, argv0], arg1, ..., opts] command name and arguments including argv[0] (no shell)

Note that env and opts are optional, as Process.spawn.

The option to pass Process.spawn is constructed by merging opts, the last hash element of the array and specification for the pipe between each commands.

Example:

Open3.pipeline_rw("tr -dc A-Za-z", "wc -c") {|i,o,ts|
  i.puts "All persons more than a mile high to leave the court."
  i.close
  p o.gets #=> "42\n"
}

Open3.pipeline_rw("sort", "cat -n") {|stdin, stdout, wait_thrs|
  stdin.puts "foo"
  stdin.puts "bar"
  stdin.puts "baz"
  stdin.close     # send EOF to sort.
  p stdout.read   #=> "     1\tbar\n     2\tbaz\n     3\tfoo\n"
}

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# File 'lib/open3.rb', line 427

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

.pipeline_start(*cmds, &block) ⇒ Object

Open3.pipeline_start starts a list of commands as a pipeline. No pipe made for stdin of the first command and stdout of the last command.

Open3.pipeline_start(cmd1, cmd2, ... [, opts]) {|wait_threads|
  ...
}

wait_threads = Open3.pipeline_start(cmd1, cmd2, ... [, opts])
...

Each cmd is a string or an array. If it is an array, the elements are passed to Process.spawn.

cmd:
  commandline                              command line string which is passed to a shell
  [env, commandline, opts]                 command line string which is passed to a shell
  [env, cmdname, arg1, ..., opts]          command name and one or more arguments (no shell)
  [env, [cmdname, argv0], arg1, ..., opts] command name and arguments including argv[0] (no shell)

Note that env and opts are optional, as Process.spawn.

Example:

# run xeyes in 10 seconds.
Open3.pipeline_start("xeyes") {|ts|
  sleep 10
  t = ts[0]
  Process.kill("TERM", t.pid)
  p t.value #=> #<Process::Status: pid 911 SIGTERM (signal 15)>
}

# convert pdf to ps and send it to a printer.
# collect error message of pdftops and lpr.
pdf_file = "paper.pdf"
printer = "printer-name"
err_r, err_w = IO.pipe
Open3.pipeline_start(["pdftops", pdf_file, "-"],
                     ["lpr", "-P#{printer}"],
                     :err=>err_w) {|ts|
  err_w.close
  p err_r.read # error messages of pdftops and lpr.
}

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# File 'lib/open3.rb', line 584

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

.pipeline_w(*cmds, &block) ⇒ Object

Open3.pipeline_w starts a list of commands as a pipeline with a pipe which connects stdin of the first command.

Open3.pipeline_w(cmd1, cmd2, ... [, opts]) {|first_stdin, wait_threads|
  ...
}

first_stdin, wait_threads = Open3.pipeline_w(cmd1, cmd2, ... [, opts])
...
first_stdin.close

Each cmd is a string or an array. If it is an array, the elements are passed to Process.spawn.

cmd:
  commandline                              command line string which is passed to a shell
  [env, commandline, opts]                 command line string which is passed to a shell
  [env, cmdname, arg1, ..., opts]          command name and one or more arguments (no shell)
  [env, [cmdname, argv0], arg1, ..., opts] command name and arguments including argv[0] (no shell)

Note that env and opts are optional, as Process.spawn.

Example:

Open3.pipeline_w("bzip2 -c", :out=>"/tmp/hello.bz2") {|i, ts|
  i.puts "hello"
}

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# File 'lib/open3.rb', line 525

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

.popen2(*cmd, &block) ⇒ Object

Open3.popen2 is similer to Open3.popen3 except it doesn't make a pipe for the standard error stream.

Block form:

Open3.popen2([env,] cmd... [, opts]) {|stdin, stdout, wait_thr|
  pid = wait_thr.pid # pid of the started process.
  ...
  exit_status = wait_thr.value # Process::Status object returned.
}

Non-block form:

stdin, stdout, wait_thr = Open3.popen2([env,] cmd... [, opts])
...
stdin.close  # stdin and stdout should be closed explicitly in this form.
stdout.close

See Process.spawn for the optional hash arguments env and opts.

Example:

Open3.popen2("wc -c") {|i,o,t|
  i.print "answer to life the universe and everything"
  i.close
  p o.gets #=> "42\n"
}

Open3.popen2("bc -q") {|i,o,t|
  i.puts "obase=13"
  i.puts "6 * 9"
  p o.gets #=> "42\n"
}

Open3.popen2("dc") {|i,o,t|
  i.print "42P"
  i.close
  p o.read #=> "*"
}

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# File 'lib/open3.rb', line 143

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

.popen2e(*cmd, &block) ⇒ Object

Open3.popen2e is similer to Open3.popen3 except it merges the standard output stream and the standard error stream.

Block form:

Open3.popen2e([env,] cmd... [, opts]) {|stdin, stdout_and_stderr, wait_thr|
  pid = wait_thr.pid # pid of the started process.
  ...
  exit_status = wait_thr.value # Process::Status object returned.
}

Non-block form:

stdin, stdout_and_stderr, wait_thr = Open3.popen2e([env,] cmd... [, opts])
...
stdin.close  # stdin and stdout_and_stderr should be closed explicitly in this form.
stdout_and_stderr.close

See Process.spawn for the optional hash arguments env and opts.

Example:

# check gcc warnings
source = "foo.c"
Open3.popen2e("gcc", "-Wall", source) {|i,oe,t|
  oe.each {|line|
    if /warning/ =~ line
      ...
    end
  }
}

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# File 'lib/open3.rb', line 192

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)
end

.popen3(*cmd, &block) ⇒ Object

Open stdin, stdout, and stderr streams and start external executable. In addition, a thread for waiting the started process is noticed. The thread has a pid method and thread variable :pid which is the pid of the started process.

Block form:

Open3.popen3([env,] cmd... [, opts]) {|stdin, stdout, stderr, wait_thr|
  pid = wait_thr.pid # pid of the started process.
  ...
  exit_status = wait_thr.value # Process::Status object returned.
}

Non-block form:

stdin, stdout, stderr, wait_thr = Open3.popen3([env,] cmd... [, opts])
pid = wait_thr[:pid]  # pid of the started process.
...
stdin.close  # stdin, stdout and stderr should be closed explicitly in this form.
stdout.close
stderr.close
exit_status = wait_thr.value  # Process::Status object returned.

The parameters cmd... is passed to Process.spawn. So a commandline string and list of argument strings can be accepted as follows.

Open3.popen3("echo abc") {|i, o, e, t| ... }
Open3.popen3("echo", "abc") {|i, o, e, t| ... }
Open3.popen3(["echo", "argv0"], "abc") {|i, o, e, t| ... }

If the last parameter, opts, is a Hash, it is recognized as an option for Process.spawn.

Open3.popen3("pwd", :chdir=>"/") {|i,o,e,t|
  p o.read.chomp #=> "/"
}

wait_thr.value waits the termination of the process. The block form also waits the process when it returns.

Closing stdin, stdout and stderr does not wait the process.

You should be careful to avoid deadlocks. Since pipes are fixed length buffer, Open3.popen3(“prog”) {|i, o, e, t| o.read } deadlocks if the program generates many output on stderr. You should be read stdout and stderr simultaneously (using thread or IO.select). However if you don't need stderr output, Open3.popen2 can be used. If merged stdout and stderr output is not a problem, you can use Open3.popen2e. If you really needs stdout and stderr output as separate strings, you can consider Open3.capture3.


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# File 'lib/open3.rb', line 82

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