/ 
Proc-Exists-0.97
River stage one • 2 direct dependents • 2 total dependents
/ Proc::Exists

NAME

Proc::Exists - quickly check for process existence

SYNOPSIS

 use Proc::Exists qw(pexists);

 my $dead_or_alive        = pexists($pid); 
 my @survivors            = pexists(@pid_list); 
 my $nsurvivors           = pexists(@pid_list); 
 my $all_pids_survived    = pexists(@pid_list, {all => 1});
 my $pid_of_one_survivor_or_undef_if_all_are_dead =
                            pexists(@pid_list, {any => 1});

FUNCTIONS

pexists( @pids, [ $args_hashref ] )

Supported arguments are 'any' and 'all', as shown above.

In list context, giving the 'any' or 'all' arguments will error out.

The 'any' argument returns the pid of the first process found, or undef if none are found. Note that on some systems, 0 is a valid and usually extant pid - see CAVEATS for more information.

DESCRIPTION

A simple and fast module for checking whether a process exists or not, regardless of whether it is a child of this process or has the same owner.

On POSIX systems, this is implemented by sending a 0 (test) signal to the pid of the process to check and examining the result and errno.

DEPENDENCIES

* any os with a POSIX layer or win32
* Test::More if you want to run 'make test'

It's possible that if you don't have a C compiler, and you're running an "obscure" UNIX-y OS (read: not linux, *BSD, solaris, or Mac OS X), you might not pass make test. This is because we need to compare the value of $! after a call to kill() with EPERM and ESRCH. Not wanting to rely on Errno or POSIX, we determine EPERM and ESRCH at build (Makefile.PL) time, by using POSIX or Errno if it exists -- but using the common values of EPERM==1 and ESRCH==3 if we can't load POSIX. If you find yourself on such a system, your best bet is to look up EPERM and ESRCH (try grepping for them down /usr/include or wherever your headers are kept). If you get hits back, you can edit Exists/Configuration.pm, add your values there, and re-run the build process. Whether you were successful or not, please send a descriptionof what you tried, as well as the output of perl -V and the results of perl misc/gather-info.pl to <ski-cpan@allafrica.com> - making sure to include Proc::Exists in the subject line (or else I won't read it!) If you had no success, hopefully I'll be able to provide a patch for you, and a fix/workaround for the next release of Proc::Exists.

There is no pure perl implementation under Windows. The solution is to use Strawberry Perl http://strawberryperl.com/.

Any other OS without a POSIX emulation layer will probably be completely non-functional (unless it implements kill()).

CAVEATS

The 'any' argument returns the pid of the first process found, or undef if none are found. Note that on some systems (e.g. OSX), 0 is a valid pid (that almost always exists). Since the 'any' mode will return the first pid that matches, a return value of 0 can indicate that a pid was found. To avoid this problem, make sure you check whether 'any' mode found anything by checking for defined-ness, not whether the result evaluates to true or false in boolean context, like so:

if(defined(pexists(@pid_list, {any => 1})));

DO NOT use this idiom:

if(pexists(@pid_list, {any => 1}));

Note also that this caveat does NOT apply for "plain" pexists() (ie without 'any' or 'all' arguments), because in scalar context a count is returned, so pexists(0) returns 1 when pid 0 exists, as expected. we only get a pid with 'any' or when we are in list context, and in the latter case, an array of length 1 containing a false value evaluates true in boolean context.

BUGS AND LIMITATIONS

Please report any bugs or feature requests through the web interface at http://rt.cpan.org.

AUTHOR

Brian Szymanski <ski-cpan@allafrica.com> -- be sure to put Proc::Exists in the subject line if you want me to read your message.

LICENCE AND COPYRIGHT

Copyright (c) 2008-2009, Brian Szymanski <ski-cpan@allafrica.com>. All rights reserved.

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

DISCLAIMER OF WARRANTY

BECAUSE THIS SOFTWARE IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE SOFTWARE, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE SOFTWARE "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE SOFTWARE IS WITH YOU. SHOULD THE SOFTWARE PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR, OR CORRECTION.

IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE SOFTWARE AS PERMITTED BY THE ABOVE LICENCE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE SOFTWARE (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE SOFTWARE TO OPERATE WITH ANY OTHER SOFTWARE), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.