Re^3: How to share streams between processes

If you need the output from both stdout and stderr via a single stream:

#main

my $kid = open my $fh, "theExternalProcess 2>&1 |" or die $!;
while( <$fh> ) {
    ## Read the output from theExternalProcess
}
## You'll end up here when the kid goes away
[download]

If you need to keep stdout and stderr separate, then see IPC::Open3 or IPC::Run.

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

"Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."

Comment on Re^3: How to share streams between processes Download Code

Replies are listed 'Best First'.
Re^4: How to share streams between processes by rapide (Beadle) on Sep 06, 2008 at 10:58 UTC
Thanks for that reply. I needed to keep them separate but managed in the end to find both a solution and the reason for me to have the trouble in the first place. Seems like I forgot to flush the stream which made it seem the processes did not work in parallel; <P> select((select(STDOUT), $\|=1)[0]); <P> And the whole script that made it all work: <br> <br>$pid = open3(CMD_IN, CMD_OUT, CMD_ERR, $path, @arguments); <br> close(CMD_IN); <br> <br> $selector = IO::Select->new(); <br> $selector->add(CMD_ERR, *CMD_OUT); <br> <br> while(@ready = $selector->can_read) { <br> foreach my $fh (@ready) { <br> if(fileno($fh) == fileno(CMD_ERR)) { <br> my $line = scalar <CMD_ERR>; <br> if(defined $line) { <br> parseErrorStream($line); <br> } <br> } <br> else { <br> my $line2 = scalar <CMD_OUT>; <br> if(defined $line2 and $print eq 1) { <br> parseStandardStream($line2); <br> } <br> } <br> $selector->remove($fh) if eof($fh); <br> } <br> } <br> close(CMD_OUT); <br> close(CMD_ERR); [download]	[reply] [d/l]

Replies are listed 'Best First'.

Re^4: How to share streams between processes
by rapide (Beadle) on Sep 06, 2008 at 10:58 UTC

Thanks for that reply. I needed to keep them separate but managed in the end to find both a solution and the reason for me to have the trouble in the first place. Seems like I forgot to flush the stream which made it seem the processes did not work in parallel;

<P> select((select(STDOUT), $|=1)[0]);
<P> And the whole script that made it all work:
<br>
<br>$pid = open3(*CMD_IN, *CMD_OUT, *CMD_ERR, $path, @arguments);
<br>  close(CMD_IN);
<br>  
<br>  $selector = IO::Select->new();
<br>  $selector->add(*CMD_ERR, *CMD_OUT);
<br>
<br>  while(@ready = $selector->can_read) {
<br>    foreach my $fh (@ready) {
<br>      if(fileno($fh) == fileno(CMD_ERR)) {
<br>        my $line = scalar <CMD_ERR>;
<br>        if(defined $line) {
<br>          parseErrorStream($line);
<br>        }
<br>      }
<br>      else {
<br>        my $line2 = scalar <CMD_OUT>;
<br>        if(defined $line2 and $print eq 1) {
<br>          parseStandardStream($line2);
<br>        }
<br>      }
<br>      $selector->remove($fh) if eof($fh);
<br>    }
<br>  }
<br>  close(CMD_OUT);
<br>  close(CMD_ERR);
[download]

[reply]
[d/l]