Module Open3
In: lib/open3.rb

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

  require "open3"
  include Open3

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

Open3.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| ... }

Methods

popen3  

Public Instance methods

popen3(*cmd) {|| ...}

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

[Source]

    # File lib/open3.rb, line 52
52:   def popen3(*cmd)
53:     pw = IO::pipe   # pipe[0] for read, pipe[1] for write
54:     pr = IO::pipe
55:     pe = IO::pipe
56: 
57:     pid = fork{
58:       # child
59:       fork{
60:         # grandchild
61:         pw[1].close
62:         STDIN.reopen(pw[0])
63:         pw[0].close
64: 
65:         pr[0].close
66:         STDOUT.reopen(pr[1])
67:         pr[1].close
68: 
69:         pe[0].close
70:         STDERR.reopen(pe[1])
71:         pe[1].close
72: 
73:         exec(*cmd)
74:       }
75:       exit!(0)
76:     }
77: 
78:     pw[0].close
79:     pr[1].close
80:     pe[1].close
81:     Process.waitpid(pid)
82:     pi = [pw[1], pr[0], pe[0]]
83:     pw[1].sync = true
84:     if defined? yield
85:       begin
86:         return yield(*pi)
87:       ensure
88:         pi.each{|p| p.close unless p.closed?}
89:       end
90:     end
91:     pi
92:   end

[Validate]