popen2

Open3.popen2 is similar to Open3.popen3 except that it doesn’t create 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 #=> "*"
}