Runaway Forking Problem (was: simple perl2)

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

this is the code ive written so far! i would be grateful if somebody could show me how to stop it spawning off a heap of processes.

#!/usr/local/bin/perl -w
for(;;) #repeat forever
      
      {
      print "please enter a command\n"; 

      $cmd = <STDIN>; #get input from keyboard
       chomp ($cmd); #remove carriage return
       if ($cmd =~/^q$/i) #if cmd is quit
         {
          exit; #exit from program
          }
         else
          {
           
          if (fork== 0) #child process created
               {
               exec $cmd; #execute the command
               }

            wait; #wait for child process to terminate
              }
              }
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Edit by neshura

Comment on Runaway Forking Problem (was: simple perl2) Download Code

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Re: simple perl2 by Beatnik (Parson) on Jun 18, 2001 at 21:02 UTC
The infinite loop does have that nasty side effect :) Try a last to end it... exit merely stops the process, in a way it breaks the loop too :) Greetz Beatnik ... Quidquid perl dictum sit, altum viditur.	[reply]
Re: simple perl2 by virtualsue (Vicar) on Jun 18, 2001 at 23:49 UTC
I have a few suggestions: You should take your fork/exec logic out of that infinite loop. If you are ending up with "heaps of processes" the loop is the main reason why. I think blindly exec-ing something from ‹STDIN› is a very bad idea. Maybe you're the only one who'll be using that program, but if I were you I'd want to examine $cmd before running it. This might be a place where taint mode would be useful. Don't leave a child process hanging about if the exec failed: `exec $cmd or die;`	[reply] [d/l]
Re: simple perl2 by DrZaius (Monk) on Jun 18, 2001 at 22:11 UTC
Try out Term::ReadLine. It will give you nice interface instead of `$cmd = <STDIN>;`. You get ctrl-(\w), as well as a command buffer that is searchable. Well, you basically get GNU Readline :) Oh yeah, don't forget to use strict :)	[reply] [d/l]