Easy way to capture STDOUT and STDERR without IPC

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

Replies are listed 'Best First'.
Re: Easy way to capture STDOUT and STDERR without IPC by toolic (Bishop) on Apr 20, 2011 at 16:30 UTC
From qx: To capture a command's STDERR and STDOUT together: 1. $output = `cmd 2>&1`; [download] Also from the FAQ's: `perldoc -q stderr` [download]	[reply] [d/l] [select]
Re: Easy way to capture STDOUT and STDERR without IPC by kennethk (Abbot) on Apr 20, 2011 at 16:33 UTC
Sure. The easiest way is using backticks (`) - see `STRING` in perlop. Grabbing both STDOUT and STDERR can be done with a little redirection in the shell: $output = `cmd 2>&1`;	[reply] [d/l]
Re: Easy way to capture STDOUT and STDERR without IPC by eff_i_g (Curate) on Apr 20, 2011 at 17:24 UTC
If you don't need the entire string and you'd rather loop you can do something like this: `open my $CMD, '-\|', 'ls 2>&1' or die $!; while (<$CMD>) { print if /\.xml/; } close $CMD or die $! ? 'Pipe failed' : 'Program error: ' . ($? >> 8) ;` [download]	[reply] [d/l]
Re: Easy way to capture STDOUT and STDERR without IPC by ikegami (Patriarch) on Apr 20, 2011 at 20:44 UTC
I'm wondering if there is an easy way to execute a shell command and simply capture all of STDERR and STDOUT into a string, potentially without using IPC. That question makes no sense. "IPC" stands for "Inter-process communication". What do you think you're doing when you're getting data from your child's STDOUT? Maybe you're trying to avoid `select`? Now that's achievable. Just like backticks lets someone else handle the IPC, there are modules that do that for more complicated cases. `use IPC::Run3 qw( run3 ); run3( \@cmd, undef, \(my $out), \(my $err) );` [download] IPC::Run3	[reply] [d/l] [select]
Re^2: Easy way to capture STDOUT and STDERR without IPC by rastoboy (Monk) on Apr 21, 2011 at 18:08 UTC
You are awesome! IPC::Run3 is just what I needed--easy peasy. Thanks!	[reply]
Re: Easy way to capture STDOUT and STDERR without IPC by johna (Monk) on Apr 20, 2011 at 20:13 UTC
Assuming your OS is some *nix flavor, the following might do what you need with a little help from `sed`: `#!/usr/bin/perl use strict; use warnings; open my $cmd, "-\|", "(SHELL_COMMAND \| sed 's/^/stdout:/') 2>&1"; my $stdout; my $stderr; while( <$cmd> ) { if( s/^stdout:// ) { $stdout .= $_; } else { $stderr .= $_; } } close $cmd; print "This is stdout:\n$stdout"; print "This is stderr:\n$stderr";` [download] It assumes that nothing printed to stderr begins with `stdout:`. If it does, choose a different string to use. -John	[reply] [d/l] [select]
Re: Easy way to capture STDOUT and STDERR without IPC by fidesachates (Monk) on Apr 20, 2011 at 20:27 UTC
Since no one has stated the obvious, I'll do so. `cmd 2> stderr.txt` By redirecting the stderr into a text file, you'll be able to read the file after the command finishes in perl and your stdout will be captured by the backticks.	[reply] [d/l]
Re: Easy way to capture STDOUT and STDERR without IPC by locked_user sundialsvc4 (Abbot) on Apr 20, 2011 at 17:36 UTC
In a Unix/Linux environment, the so-called “piping” of input/output is ... “the way that things get done in this here neck of the woods.” Every command has one input stream (STDIN) and two output streams, and the entire system is geared around the notion of doing things by stringing the services of several simpler programs together. The shell can do it. Easy as fallin’ off a log... All the IPC monkey-biz that needs to be done “just happens.”
Re^2: Easy way to capture STDOUT and STDERR without IPC by rastoboy (Monk) on Apr 20, 2011 at 19:08 UTC
So how can you capture STDOUT and STDERR separately?	[reply]