NAME IO::CaptureOutput - capture STDOUT and STDERR from Perl code, subprocesses or XS VERSION This documentation describes version 1.08. SYNOPSIS use IO::CaptureOutput qw(capture capture_exec); my ($stdout, $stderr); sub noisy { warn "this sub prints to stdout and stderr!"; print "arguments: @_"; } capture { noisy(@args) } \$stdout, \$stderr; ($stdout, $stderr) = capture_exec( 'perl', '-e', 'print "Hello"; print STDERR "World!"'); DESCRIPTION This module provides routines for capturing STDOUT and STDERR from perl subroutines, forked system calls (e.g. "system()", "fork()") and from XS or C modules. FUNCTIONS The following functions will be exported on demand. capture() capture \&subroutine, \$stdout, \$stderr; Captures everything printed to "STDOUT" and "STDERR" for the duration of &subroutine. $stdout and $stderr are optional scalars that will contain "STDOUT" and "STDERR" respectively. "capture()" uses a code prototype so the first argument can be specified directly within brackets if desired. # shorthand with prototype capture { print __PACKAGE__ } \$stdout, \$stderr; Returns the return value(s) of &subroutine. The sub is called in the same context as "capture()" was called e.g.: @rv = capture { wantarray } ; # returns true $rv = capture { wantarray } ; # returns defined, but not true capture { wantarray }; # void, returns undef "capture()" is able to capture output from subprocesses and C code, which traditional "tie()" methods of output capture are unable to do. Note: "capture()" will only capture output that has been written or flushed to the filehandle. If the two scalar references refer to the same scalar, then "STDERR" will be merged to "STDOUT" before capturing and the scalar will hold the combined output of both. capture \&subroutine, \$combined, \$combined; Normally, "capture()" uses anonymous, temporary files for capturing output. If desired, specific file names may be provided instead as additional options. capture \&subroutine, \$stdout, \$stderr, $out_file, $err_file; Files provided will be clobbered, overwriting any previous data, but will persist after the call to "capture()" for inspection or other manipulation. By default, when no references are provided to hold STDOUT or STDERR, output is captured and silently discarded. # Capture STDOUT, discard STDERR capture \&subroutine, \$stdout; # Discard STDOUT, capture STDERR capture \&subroutine, undef, \$stderr; If either STDOUT or STDERR should be passed through to the terminal instead of captured, provide a reference to undef -- "\undef" -- instead of a capture variable. # Capture STDOUT, display STDERR capture \&subroutine, \$stdout, \undef; # Display STDOUT, capture STDERR capture \&subroutine, \undef, \$stderr; capture_exec() ($stdout, $stderr) = capture_exec(@args); Captures and returns the output from "system(@args)". In scalar context, "capture_exec()" will return what was printed to "STDOUT". In list context, it returns what was printed to "STDOUT" and "STDERR" $stdout = capture_exec('perl', '-e', 'print "hello world"'); ($stdout, $stderr) = capture_exec('perl', '-e', 'warn "Test"'); "capture_exec" passes its arguments to "system()" and on MSWin32 will protect arguments with shell quotes if necessary. This makes it a handy and slightly more portable alternative to backticks, piped "open()" and "IPC::Open3". You can check the exit status of the "system()" call with the $? variable. See perlvar for more information. capture_exec_combined() $combined = capture_exec_combined( 'perl', '-e', 'print "hello\n"', 'warn "Test\n" ); This is just like "capture_exec()", except that it merges "STDERR" with "STDOUT" before capturing output and returns a single scalar. Note: there is no guarantee that text printed to "STDOUT" and "STDERR" in the subprocess will be appear in order. The actual order will depend on how IO buffering is handled in the subprocess. qxx() This is an alias for "capture_exec()". qxy() This is an alias for "capture_exec_combined()". SEE ALSO * IPC::Open3 * IO::Capture * IO::Utils AUTHORS * Simon Flack (original author) * David Golden (co-maintainer since version 1.04) COPYRIGHT AND LICENSE Portions copyright 2004, 2005 Simon Flack. Portions copyright 2007 David Golden. All rights reserved. You may distribute under the terms of either the GNU General Public License or the Artistic License, as specified in the Perl README file.