# Open4-0.2.0

**URL:** <https://www.ruby-forum.com/t/open4-0-2-0/67763>\
**Category:** Ruby\
**Created:** [February 14, 2006, 6:28am UTC](https://www.ruby-forum.com/t/open4-0-2-0/67763 "2006-02-14T06:28:07Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![unknown](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/u/4bbf92/32.png) [@unknown](https://www.ruby-forum.com/u/unknown)\
**Post date:** [February 14, 2006, 6:28am UTC](https://www.ruby-forum.com/t/open4-0-2-0/67763/1 "2006-02-14T06:28:07Z")

</div>

URIS

[http://rubyforge.org/frs/?group\_id=1024](http://rubyforge.org/frs/?group_id=1024)  
[http://www.codeforpeople.com/lib/ruby/](http://www.codeforpeople.com/lib/ruby/)

SYNOPSIS

open child process with handles on pid, stdin, stdout, and stderr

HISTORY

0.2.0 :  
- added exception marshaled from child → parent when exec fails.  
thanks  
to jordan breeding for a patch (yay!) and paul brannan for this  
most  
excellent idea.

0.1.0 :  
- fixed docs to correctly show return value of popen4 (pid first  
not last).  
thanks Stefanie T. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) for catching this.  
0.0.0 :  
- initial version

INSTALL

~\> gem install open4

SAMPLES

simple usage:

```
 jib:~/eg/ruby/open4/open4-0.2.0 > cat sample/simple.rb
 require "open4"

 pid, stdin, stdout, stderr = Open4::popen4 "sh"

 stdin.puts "echo 42.out"
 stdin.puts "echo 42.err 1>&2"
 stdin.close

 ignored, status = Process::waitpid2 pid

 puts "pid : #{ pid }"
 puts "stdout : #{ stdout.read.strip }"
 puts "stderr : #{ stderr.read.strip }"
 puts "status : #{ status.inspect }"
 puts "exitstatus : #{ status.exitstatus }"

 jib:~/eg/ruby/open4/open4-0.2.0 > ruby sample/simple.rb
 pid : 17273
 stdout : 42.out
 stderr : 42.err
 status : #<Process::Status: pid=17273,exited(0)>
 exitstatus : 0

```

block form - child process is automatically waited for:

```
 jib:~/eg/ruby/open4/open4-0.2.0 > cat sample/block.rb
 require 'open4'

 status =
   Open4::popen4("sh") do |pid, stdin, stdout, stderr|
     stdin.puts "echo 42.out"
     stdin.puts "echo 42.err 1>&2"
     stdin.close

     puts "pid : #{ pid }"
     puts "stdout : #{ stdout.read.strip }"
     puts "stderr : #{ stderr.read.strip }"
   end

     puts "status : #{ status.inspect }"
     puts "exitstatus : #{ status.exitstatus }"

 jib:~/eg/ruby/open4/open4-0.2.0 > ruby sample/block.rb
 pid : 17295
 stdout : 42.out
 stderr : 42.err
 status : #<Process::Status: pid=17295,exited(0)>
 exitstatus : 0

```

exceptions are marshaled from child to parent if fork/exec fails:

```
 jib:~/eg/ruby/open4/open4-0.2.0 > cat sample/exception.rb
 require "open4"
 Open4::popen4 "noexist"

 jib:~/eg/ruby/open4/open4-0.2.0 > ruby sample/exception.rb
 /dmsp/reference/ruby-1.8.1//lib/ruby/site_ruby/open4.rb:100:in 

```

`popen4’: No such file or directory - noexist (Errno::ENOENT)  
from sample/exception.rb:3

AUTHOR

removed\_email\_address@domain.invalid

LICENSE

ruby’s

enjoy.

-a