method

popen3

v1_8_7_330 - Show latest stable - Class: Open3

popen3(*cmd)

public

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 lib/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

popen3

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