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Open3

Open3 grants you access to stdin, stdout, and stderr when running another program. Example:

require "open3"
include Open3

stdin, stdout, stderr = popen3('nroff -man')

::popen3 can also take a block which will receive stdin, stdout and stderr as parameters. This ensures stdin, stdout and stderr are closed once the block exits. Example:

require "open3"

Open3.popen3('nroff -man') { |stdin, stdout, stderr| ... }

Public Class Methods

popen3(*cmd) click to toggle source

Open stdin, stdout, and stderr streams and start external executable. Non-block form:

require 'open3'

stdin, stdout, stderr = Open3.popen3(cmd)

Block form:

require 'open3'

Open3.popen3(cmd) { |stdin, stdout, stderr| ... }

The parameter cmd is passed directly to Kernel#exec.

popen3 is like system in that you can pass extra parameters, and the strings won't be mangled by shell expansion.

stdin, stdout, stderr = Open3.popen3('identify', '/weird path/with spaces/and "strange" characters.jpg')
result = stdout.read
 
               # File open3.rb, line 52
def popen3(*cmd)
  pw = IO::pipe   # pipe[0] for read, pipe[1] for write
  pr = IO::pipe
  pe = IO::pipe

  pid = fork{
    # child
    fork{
      # grandchild
      pw[1].close
      STDIN.reopen(pw[0])
      pw[0].close

      pr[0].close
      STDOUT.reopen(pr[1])
      pr[1].close

      pe[0].close
      STDERR.reopen(pe[1])
      pe[1].close

      exec(*cmd)
    }
    exit!(0)
  }

  pw[0].close
  pr[1].close
  pe[1].close
  Process.waitpid(pid)
  pi = [pw[1], pr[0], pe[0]]
  pw[1].sync = true
  if defined? yield
    begin
      return yield(*pi)
    ensure
      pi.each{|p| p.close unless p.closed?}
    end
  end
  pi
end