/ 
IPC-Run3-0.005
River stage four • 129 direct dependents • 5146 total dependents
/ IPC::Run3

NAME

IPC::Run3 - Run a subprocess in batch mode (a la system) on Unix, Win32, etc.

SYNOPSIS

use IPC::Run3;    ## Exports run3() by default
use IPC::Run3 (); ## Don't pollute

DESCRIPTION

This module allows you to run a subprocess and redirect stdin, stdout, and/or stderr to files and perl data structures. It aims to satisfy 99% of the need for using system()/qx``/open3() with a simple, extremely Perlish API and none of the bloat and rarely used features of IPC::Run.

Speed (of Perl code; which is often much slower than the kind of buffered I/O that this module uses to spool input to and output from the child command), simplicity, and portability are paramount. Disk space is not.

Note that passing in \undef explicitly redirects the associated file descriptor for STDIN, STDOUT, or STDERR from or to the local equivalent of /dev/null. Passing in "undef" (or not passing a redirection) allows the child to inherit the corresponding STDIN, STDOUT, or STDERR from the parent.

Because the redirects come last, this allows STDOUT and STDERR to default to the parent's by just not specifying them; a common use case.

Note: This means that:

run \@cmd, undef, \$out;   ## Pass on parent's STDIN

does not close the child's STDIN, it passes on the parent's. Use

run \@cmd, \undef, \$out;  ## Close child's STDIN

for that.

If the exact same value is passed for $stdout and $stderr, then the child will write both to the same filehandle. In general, this means that

run \@cmd, \undef, "foo.txt", "foo.txt";
run \@cmd, \undef, \$out, \$out;

will DWYM and only require one set of reads.

DEBUGGING

To enable debugging use the IPCRUN3DEBUG environment variable to a non-zero integer value:

$ IPCRUN3DEBUG=1 myapp

.

COMPARISON

Here's how it stacks up to existing APIs:

system(), qx'', open "...|", open "|..."
+

redirects more that one file descriptor

+

returns TRUE on success, FALSE on failure

+

throws an error if problems occur in the parent process (or the pre-exec child)

+

allows a very perlish interface to perl data structures

+

allows 1 word invocations to avoid the shell easily.

-

leaves the result in $?

open2(), open3()
+

No need to risk a deadlock or avoid it with a length select() loop

+

Hides OS dependancies

+

Parameter order is like open3() (not like open2()).

+

Synchronizes with the child process so you get an exception if the child process fails to run.

IPC::Run::run()
+

Smaller, lower overhead, simpler, more portable

+

No select() loop

+

Does not fall prey to Perl closure leaks

-

Does not allow interaction with the subprocess (which IPC::Run::run() allows by redirecting subroutines).

-

Lacks many features of IPC::Run::run() (filters, pipes, redirects, pty support).

TODO

pty support

LIMITATIONS

Often uses intermediate files (determined by File::Temp, and thus by the File::Spec defaults and the TMPDIR env. variable) for speed, portability and simplicity.

COPYRIGHT

Copyright 2003, R. Barrie Slaymaker, Jr., All Rights Reserved

LICENSE

You may use this module under the terms of the BSD, Artistic, or GPL licenses, any version.

AUTHOR

Barrie Slaymaker <barries@slaysys.com>