#!/usr/bin/perl -w

# Program: printsth
print join (' ', @ARGV), $/ for (1..10);
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Now I call this program inside another program and capture it's output

#!/usr/bin/perl -w

# Program: captpipe

my $arg = "hi there";

print ("Going to call another perl program and capture it's output\n")
+;

open (PIPE,"printsth $arg | ") or die $!;

while (<PIPE>) {
        print;
}
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when you just run  printsth hi there you will get  hi there\n 10 times.

when you execute the captpipe script you will see the same output.

Output

[sk]% captpipe
Going to call another perl program and capture it's output
hi there
hi there
hi there
hi there
hi there
hi there
hi there
hi there
hi there
hi there
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this is a better way to capture output than using backticks!

Yay! I used the open (PIPE,"blah") method and it worked!

I had a feeling it was something to do with the depth and complexity of the piping and stdout reading that was causing it - using this different method must have corrected that.

Thanks sk !

Drew

Yay! I used the open (PIPE,"blah") method and it worked!

Seeing what you chose to omit in your shortened rendition of the method, I hope you realize that what matters here is not the name "PIPE" for the handle, but the | at the end of the second argument to open. I.e. it would have worked just as well if you had used

open( THIS_IS_NOT_A_PIPE,"printsth $arg |" ) or die $!;

while ( <THIS_IS_NOT_A_PIPE> ) {
  print;
}
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(With apologies to Magritte.)

the lowliest monk

When I run this:

use warnings;
use strict;

print `Perl noname2.pl`;
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where noname2.pl contains:

use warnings;
use strict;

print "This is noname2.pl\n";
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I get:

This is noname2.pl
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which is what I would expect. What are you doing that is different?

For a start, thanks for your help :->

I wasn't using "print `blah`;", so I tried that, but it hasn't made any difference.

The script I am writing is called by another Perl script, which expects my script to produce lines from web server logs (so lots and lots of output). My script calls another script which actually reads the web server logs and organises them chronologically, then outputs the lines to stdout.

What I need is for my script to "pass through" the stdout output from the script I call, and output it on it's own stdout.

So at the moment, I construct a command (as an array) from a number of variables concatenated together (and when I print this command without executing it, it looks correct), and then I was calling it using "system()", but I realised after looking in the Perl docs that system() will only return the exit code of the command it called, so that is obviously no use to me.

Then I found that calling a command using backticks apparently lets you see the output of the command, but I must still be doing something wrong, as it doesn't.

Drew

Hang on, let me try that ...

Drew

my $memout = `chcp`;
$memout =~ /(\d+)/;
print STDERR "Detected code page $1 ... continuing\n";
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I hope that's not the problem, as I have to run this on a production system under Windows Server 2003, and I'd rather not use Cygwin (which I have used with bash scripts instead to achieve the same results)

Drew

AFAIK, It should not cause any problems on windows... I tried the same script on my XP Pro SP2 machine and works just fine. I am on AS 5.8.7.

On windows I couldn't get the shebangs to work well. If you have similar issues then you should change the open to  open (PIPE,"perl printsth $arg | ");

cheers

SK