NAME¶
IO::CaptureOutput - capture STDOUT and STDERR from Perl code, subprocesses or XS
VERSION¶
This documentation describes version 1.1102.
SYNOPSIS¶
use IO::CaptureOutput qw(capture qxx qxy);
# STDOUT and STDERR separately
capture { noisy_sub(@args) } \$stdout, \$stderr;
# STDOUT and STDERR together
capture { noisy_sub(@args) } \$combined, \$combined;
# STDOUT and STDERR from external command
($stdout, $stderr, $success) = qxx( @cmd );
# STDOUT and STDERR together from external command
($combined, $success) = qxy( @cmd );
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;
However, even when using "undef", output can be captured to specific
files.
# Capture STDOUT to a specific file, discard STDERR
capture \&subroutine, \$stdout, undef, $outfile;
# Discard STDOUT, capture STDERR to a specific file
capture \&subroutine, undef, \$stderr, undef, $err_file;
# Discard both, capture merged output to a specific file
capture \&subroutine, undef, undef, $mergedfile;
It is a fatal error to merge STDOUT and STDERR and request separate, specific
files for capture.
# ERROR:
capture \&subroutine, \$stdout, \$stdout, $out_file, $err_file;
capture \&subroutine, undef, undef, $out_file, $err_file;
If either STDOUT or STDERR should be passed through to the terminal instead of
captured, provide a reference to undef -- "\undef" -- instead of a
capture variable.
# Capture STDOUT, display STDERR
capture \&subroutine, \$stdout, \undef;
# Display STDOUT, capture STDERR
capture \&subroutine, \undef, \$stderr;
capture_exec()¶
($stdout, $stderr, $success, $exit_code) = 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" as well as a success flag and the
exit value.
$stdout = capture_exec('perl', '-e', 'print "hello world"');
($stdout, $stderr, $success, $exit_code) =
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".
The $success flag returned will be true if the command ran successfully and
false if it did not (if the command could not be run or if it ran and returned
a non-zero exit value). On failure, the raw exit value of the
"system()" call is available both in the $exit_code returned and in
the $? variable.
($stdout, $stderr, $success, $exit_code) =
capture_exec('perl', '-e', 'warn "Test" and exit 1');
if ( ! $success ) {
print "The exit code was " . ($exit_code >> 8) . "\n";
}
See perlvar for more information on interpreting a child process exit code.
capture_exec_combined()¶
($combined, $success, $exit_code) = 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.
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
- •
- IPC::System::Simple
AUTHORS¶
- •
- Simon Flack <simonflk _AT_ cpan.org> (original
author)
- •
- David Golden <dagolden _AT_ cpan.org> (co-maintainer
since version 1.04)
COPYRIGHT AND LICENSE¶
Portions copyright 2004, 2005 Simon Flack. Portions copyright 2007, 2008 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.