my pipes

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

iam trying to create a program which will accept up to three commands pipe them and execute them. so far my program keeps crashing any help would be appreciated below is my program:

#!/usr/local/bin/perl -w
# perl script to pipe up to 3 commands together

$cmd=<STDIN>; #get input
chomp($cmd); #remove carriage return
@cmd=split(#,$cmd); #seperate commands by a #
$max=3; #set max size of array to 3
$max=@cmd; #assign size to array cmd
$max=$max-1;  #let the array start at 0

for($x=1;$x<$max-1;$x++){ #go through each element of the array

if(fork==0)
{ #do the first command
 for($n=1;$n<$max-1;$n++) #close all input pipes
    close INPIPE[$n];

  for($p=2;$p<$max-1$p++) #close all the output pipes
      close OUTPIPE[$p]; #except the last one

 close STDOUT;
open STDOUT">&OUTPIPE[1]"; #first output pipe still open
exec cmd[1];#execute the first command
}

elseif (x=max-1) #second command

{

for($n=1;$n<max-1;$n++) #close all input pipes
if n!=x-1
close INPIPE[$n];

if n!=x-1
close OUTPIPE[$n]; #close outpipe

close STDIN; #close STDIN
open STDIN">&INPIPE[n-1];

close STDOUT; #close STDOUT
open STDOUT">&OUTPIPE[n];

exec cmd[2];
}
elseif(x=max) #last command
for($n=1;$n<max-2;$n++) #close all input pipes
Close INPIPE[$n];

for($p=1;$p<$max-1;$p++) #close all output pipes
close INPIPE[$p]; #close INPIPE

close STDIN;
open STDIN">&INPIPE[max];

exec cmd[3]; #execute the last command

}

}
for($d=1; $d<$max-1; $d++)
{
close INPIPE[$d]; #close INPIPES
close OUTPIPE[$d]; #close outpipes
}
for($s=1;$s<$max-1;$s++)
{
wait; # wait for the child process
}

{
[download]

Edit Masem - 2001-07-24 - Added CODE tags (sic)

Comment on my pipes Download Code

Replies are listed 'Best First'.
Re: my pipes by wine (Scribe) on Jul 23, 2001 at 14:00 UTC
Well, um, you're code looks horrible with a lot of bug and won't compile. I wonder why you want to use perl for this task. You don't really use the output or something. I'd use a shell script. For sh: `#!/bin/sh # # some variations for executing 3 commands $1 ; $2 ; $3 # commands get executed after one another $1 && $2 && $3 # commands get only executed if previous succeeds $1 & $2 & $3 & # commands get forked # well you get the point, man sh for more ...` [download] - Good luck	[reply] [d/l]
Re: my pipes by bwana147 (Pilgrim) on Jul 23, 2001 at 13:47 UTC
Please, please, use <code> tags so your code stands out as code. Still I tried and read your post, and it doesn't seem it can survive a `use strict`. So start by adding this on top of your code: `#!/usr/local/bin/perl use strict; use warnings use diagnostics; ... your code here...` [download] When you're rid of all error messages, and your code still doesn't work as expected, then you can come back here. --bwana147	[reply] [d/l] [select]
Re: my pipes by mattr (Curate) on Jul 23, 2001 at 13:41 UTC
Sorry this post was virtually unreadable. Could you repost as a reply, using <code> .. </code> please.	[reply]