# Executing program from ruby **URL:** \ **Category:** Ruby\ **Created:** [April 19, 2007, 3:22pm UTC](https://www.ruby-forum.com/t/executing-program-from-ruby/92443 "2007-04-19T15:22:48Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![marcin\_r](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/e5b9ba/32.png) [@marcin\_r](https://www.ruby-forum.com/u/marcin_r)\ **Post date:** [April 19, 2007, 3:22pm UTC](https://www.ruby-forum.com/t/executing-program-from-ruby/92443/1 "2007-04-19T15:22:48Z")
Hello i know there are several ways to execute from within ruby but each one have their own problems: `` doesn’t check if command /programm runs at all!, also it blocks untill command returns, no bi-directional comunication popen2,3,4 doesn’t check if command exists at all … it’s not rising any errors … and happilly continues to run untill you try to write something to pipe that leads to program that never even started only system() checks if command runs but it also returns false when programs starts but returns anything other then 0 does anyone know good way to check if command exists then run it, return pid for monitoring purposes and allow bidirectional comunication, then check exit status ? open4 comes close to fulfilling all that but it doesn’t rise (sample program that tells you it’ll doesn’t eaither), not to mention compleate lack of documentation. any expirience with open4? help? pointers? mayby i’m simply missing some obvious way? ---
**Author:** ![marcin\_r](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/e5b9ba/32.png) [@marcin\_r](https://www.ruby-forum.com/u/marcin_r)\ **Post date:** [April 19, 2007, 3:30pm UTC](https://www.ruby-forum.com/t/executing-program-from-ruby/92443/2 "2007-04-19T15:30:51Z")
On 19.04.2007 15:21, Marcin R. wrote: > starts but returns anything other then 0 > mayby i’m simply missing some obvious way? > popen and its derivatives? robert ---
**Author:** ![marcin\_r](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/e5b9ba/32.png) [@marcin\_r](https://www.ruby-forum.com/u/marcin_r)\ **Post date:** [April 19, 2007, 3:35pm UTC](https://www.ruby-forum.com/t/executing-program-from-ruby/92443/3 "2007-04-19T15:35:52Z")
On Apr 19, 2007, at 8:21 AM, Marcin R. wrote: > any expirience with open4? help? pointers? TextMate uses a hand-rolled popen3(), which is really just an open4() clone. Allan Odgaard, the creator of TextMate, wrote the code, but it’s straightforward enough that I thought it might help you to see it: def my\_popen3(\*cmd) # returns [stdin, stdout, strerr, pid] pw = IO::pipe # pipe[0] for read, pipe[1] for write pr = IO::pipe pe = IO::pipe pid = fork{ 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) ``` } pw[0].close pr[1].close pe[1].close pw[1].sync = true [pw[1], pr[0], pe[0], pid] end Hope that helps. James Edward G. II ---
**Author:** ![marcin\_r](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/e5b9ba/32.png) [@marcin\_r](https://www.ruby-forum.com/u/marcin_r)\ **Post date:** [April 19, 2007, 3:50pm UTC](https://www.ruby-forum.com/t/executing-program-from-ruby/92443/4 "2007-04-19T15:50:56Z")
On Thursday 19 April 2007 13:34, James Edward G. II wrote: > pe = IO::pipe > pe[0].close > pw[1].sync = true > > [pw[1], pr[0], pe[0], pid] > end > > Hope that helps. > > James Edward G. II code is really simmilar to opn4 i understand how it works (i follow "don’t use wizard/library you don’t understand " rule) … and to be honest i can write it myself, but i thought there’s solution for problem already :] well popen 3/4 is almost good enought … but if you use it with block it doesn’t check if command was executed at all!!! i need to do something like this: check if command exists… try to run it… if there’s problem (no privilages etc.) do some work about that , notify user etc. if program started write to it’s stdin and get answer. popen4 should do exactly that … but sample that should rise error doesn’t do that, not to mention there’s no documentation except changelog and few samples. thnx for reply tho ---
**Author:** ![marcin\_r](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/e5b9ba/32.png) [@marcin\_r](https://www.ruby-forum.com/u/marcin_r)\ **Post date:** [April 20, 2007, 3:47pm UTC](https://www.ruby-forum.com/t/executing-program-from-ruby/92443/5 "2007-04-20T15:47:14Z")
On Thursday 19 April 2007 15:04, removed\_email\_address@domain.invalid wrote: > > only system() checks if command runs but it also returns false when > > file or directory - no-exist (Errno::ENOENT) from > /home/ahoward/eg/ruby/open4/open4-0.9.3 > /home/ahoward/nfs//lib/ruby/site\_ruby/1.8/open4.rb:37:in `popen4’ from > ?? > > > mayby i’m simply missing some obvious way? > > i wrote open4 - so i’m expirienced with it 😉 can you give and example of > exactly what you’re trying to do? > > regards. > > -a i sent you example on e-mail, but it was my fault… in you examples there’s no require ‘rubygems’, and it’s required to work, if not it loads standard open4 library 😕 took me 2h to figure that out. preaty good library tho (at least when i got it to work) ---
**Author:** ![marcin\_r](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/e5b9ba/32.png) [@marcin\_r](https://www.ruby-forum.com/u/marcin_r)\ **Post date:** [April 19, 2007, 5:05pm UTC](https://www.ruby-forum.com/t/executing-program-from-ruby/92443/6 "2007-04-19T17:05:12Z")
On Thu, 19 Apr 2007, Marcin R. wrote: > starts but returns anything other then 0 > > does anyone know good way to check if command exists then run it, return pid > for monitoring purposes and allow bidirectional comunication, then check exit > status ? > > open4 comes close to fulfilling all that but it doesn’t rise (sample program > that tells you it’ll doesn’t eaither), ?? harp:~ \> ruby -r open4 -e’ Open4.popen4 “no-exist” ’ /home/ahoward//lib/ruby/site\_ruby/1.8/open4.rb:37:in `exec': No such file or directory - no-exist (Errno::ENOENT) from /home/ahoward//lib/ruby/site_ruby/1.8/open4.rb:37:in `popen4’ from /home/ahoward//lib/ruby/site\_ruby/1.8/open4.rb:21:in `popen4’ from -e:1 harp:~ \> ruby -r open4 -e’ Open4.spawn “no-exist” ’ /home/ahoward//lib/ruby/site\_ruby/1.8/open4.rb:37:in `exec': No such file or directory - no-exist (Errno::ENOENT) from /home/ahoward//lib/ruby/site_ruby/1.8/open4.rb:37:in `popen4’ from /home/ahoward//lib/ruby/site\_ruby/1.8/open4.rb:21:in `popen4' from /home/ahoward//lib/ruby/site_ruby/1.8/open4.rb:273:in `spawn’ from /home/ahoward//lib/ruby/1.8/timeout.rb:38:in `timeout' from /home/ahoward//lib/ruby/site_ruby/1.8/open4.rb:272:in `spawn’ from -e:1 from the dist harp:open4-0.9.3 \> pwd /home/ahoward/eg/ruby/open4/open4-0.9.3 harp:open4-0.9.3 \> cat sample/exception.rb require “open4” Open4::popen4 “noexist” harp:open4-0.9.3 \> ruby sample/exception.rb /home/ahoward/nfs//lib/ruby/site\_ruby/1.8/open4.rb:37:in `exec': No such file or directory - noexist (Errno::ENOENT) from /home/ahoward/nfs//lib/ruby/site_ruby/1.8/open4.rb:37:in `popen4’ from /home/ahoward/nfs//lib/ruby/site\_ruby/1.8/open4.rb:21:in `fork' from /home/ahoward/nfs//lib/ruby/site_ruby/1.8/open4.rb:21:in `popen4’ from sample/exception.rb:3 can you show an exampe which does not work? > not to mention compleate lack of \> documentation. ?? [http://codeforpeople.com/lib/ruby/open4/open4-0.9.3/README](http://codeforpeople.com/lib/ruby/open4/open4-0.9.3/README) this covers nearly every part of open4. if you need more, there is [http://codeforpeople.com/lib/ruby/open4/open4-0.9.3/lib/open4.rb](http://codeforpeople.com/lib/ruby/open4/open4-0.9.3/lib/open4.rb) it is an extremely small library > any expirience with open4? help? pointers? > mayby i’m simply missing some obvious way? i wrote open4 - so i’m expirienced with it 😉 can you give and example of exactly what you’re trying to do? regards. -a