Test2::Harness::Util::IPC - Utilities for IPC management.


This package provides low-level IPC tools for Test2::Harness.


All exports are optional and must be specified at import time.

$bool = USE_P_GROUPS()

This is a shortcut for:

    use Config qw/%Config/;
swap_io($from, $to)
swap_io($from, $to, \&die)

This will close and re-open the file handle designated by $from so that it redirects to the handle specified in $to. It preserves the file descriptor in the process, and throws an exception if it fails to do so.

    swap_io(\*STDOUT, $fh);
    # STDOUT now points to wherever $fh did, but maintains the file descriptor number '2'.

As long as the file descriptor is greater than 0 it will open for writing. If the descriptor is 0 it will open for reading, allowing for a swap of STDIN as well.

Extra effort is made to insure errors go to the real STDERR, specially when trying to swap out STDERR. If you have trouble with this, or do not trust it, you can provide a custom coderef as a third argument, this coderef will be used instead of die() to throw exceptions.

Note that the custom die logic when you do not provide your own bypasses the exception catching mechanism and will exit your program. If this is not desirable then you should provide a custom die subref.

$pid = run_cmd(command => [...], %params)

This function will run the specified command and return a pid to you. When possible this will be done via fork() and exec(). When that is not possible it uses the system(1, ...) trick to spawn a new process. Some parameters do not work in the second case, and are silently ignored.


command => [$command, sub { ... }, @args]
command => sub { return ($command, @args) }

This parameter is required. This should either be an arrayref of arguments for exec(), or a coderef that returns a list of arguments for exec(). On systems without fork/exec the arguments will be passed to system(1, $command, @args) instead.

If the command arrayref has a coderef in it, the coderef will be run and its return value(s) will be inserted in its place. This replacement happens post-chroot

run_in_parent => [sub { ... }, sub { ... }]

An arrayref of callbacks to be run in the parent process immedietly after the child process is started.

run_in_child => [sub { ... }, sub { ... }]

An arrayref of callbacks to be run in the child process immedietly after fork. This parameter is silently ignored on systems without fork/exec.

env => { ENVVAR => $VAL, ... }

A hashref of custom environment variables to set in the child process. In the fork/exec model this is done post-fork, in the spawn model this is done via local prior to the spawn.

no_set_pgrp => $bool,

Normall setpgrp(0,0) is called on systems where it is supported. You can use this parameter to override the normal behavior. setpgrp() is not called in the spawn model, so this parameter is silently ignored there.

chdir => 'path/to/dir'
ch_dir => 'path/to/dir'

chdir() to the specified directory for the new process. In the fork/exec model this is done post-fork in the child. In the spawn model this is done before the spawn, then a second chdir() puts the parent process back to its original dir after the spawn.

stdout => $handle
stderr => $handle
stdin => $handle

Thise can be used to provide custom STDERR, STDOUT, and STDIN. In the fork/exec model these are swapped into place post-fork in the child. In the spawn model the swap occurs pre-spawn, then the old handles are swapped back post-spawn.


The source code repository for Test2-Harness can be found at


Chad Granum <>


Chad Granum <>


Copyright 2020 Chad Granum <>.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.