Provided by: libparanoid-perl_2.05-2_all 
NAME
Paranoid::Process - Process Management Functions
VERSION
$Id: lib/Paranoid/Process.pm, 2.05 2017/02/06 01:48:57 acorliss Exp $
SYNOPSIS
use Paranoid::Process qw(:all);
$rv = daemonize();
MAXCHILDREN = 100;
$SIG{CHLD} = \&sigchld;
$count = childrenCount();
installChldHandler(&cleanup);
$rv = pfork();
$uid = ptranslateUser("foo");
$gid = ptranslateGroup("foo");
$rv = switchUser($user, $group);
$rv = pcapture($cmd, $crv, $out);
installSIGH('INT', &sigint1):
installSIGH('INT', &sigint2):
installSIGH('INT', &sigint3):
uninstallSIGH('INT', &sigint2);
installSIGD();
uninstallSIGD();
DESCRIPTION
This module provides a few functions meant to make life easier when managing processes.
The following export targets are provided:
all All functions within this module
pfork All child management functions
signal All signal dispatcher functions
Only the functions switchUser and daemonize are currently exported by default.
SUBROUTINES/METHODS
MAXCHILDREN
Setting this lvalue subroutine sets a limit to how many children will be forked at a time
by pfork. The default is zero, which allows unlimited children. Once the limit is met
pfork becomes a blocking call until a child exits so the new one can be spawned.
childrenCount
$count = childrenCount();
This function returns the current number of children spawned by pfork.
installChldHandler
installChldHandler(&cleanup);
This function takes a reference to a subroutine. If used the subroutine will be called
every time a child exits. That subroutine will be called with the child's PID and exit
value as arguments.
sigchld
$SIG{CHLD} = \&sigchld;
# Or, if using the signal dispatcher
installSIGH('CHLD', &sigchld);
installSIGD();
This function decrements the child counter necessary for pfork's operation, as well as
calling the user's signal handler with each child's PID and exit value.
daemonize
$rv = daemonize();
This function forks a child who reopens all STD* filehandles on /dev/null and starts a new
process group. The parent exits cleanly. If the fork fails for any reason it returns a
false value. The child will also change its directory to /.
pfork
$rv = pfork();
This function should be used in lieu of Perl's fork if you want to take advantage of a
blocking fork call that respects the MAXCHILDREN limit. Use of this function, however,
also assumes the use of sigchld as the signal handler for SIGCHLD.
ptranslateUser
$uid = ptranslateUser("foo");
This function takes a username and returns the corresponding UID as returned by getpwent.
If no match is found it returns undef.
ptranslateGroup
$gid = ptranslateGroup("foo");
This function takes a group name and returns the corresponding GID as returned by
getgrent. If no match is found it returns undef.
switchUser
$rv = switchUser($user);
$rv = switchUser($user, $group);
This function can be fed one or two arguments, both either named user or group, or UID or
GID. Both user and group arguments are optional as long as one of them is defined.
pcapture
$rv = pcapture($cmd, $crv, $out);
This function executes the passed shell command and returns one of the following three
values:
RV Description
=======================================================
-1 Command failed to execute or died with signal
0 Command executed but exited with a non-0 RV
1 Command executed and exited with a 0 RV
The actual return value is populated in the passed scalar, while all command output
(including STDERR) is stored in the next scalar. Any errors executing the command will
have the error string stored in Paranoid::ERROR.
If the command exited cleanly it will automatically be bit shifted eight bits.
NOTE: Unlike many other functions in this suite it is up to you to detaint the command
passed to this function yourself. There's simply no way for me to know ahead of time what
kind of convoluted arguments you might be handing this call before system is called.
Failing to detaint that argument will cause your script to exit under taint mode.
installSIGH
installSIGH($signal, &subroutine);
This installs another subroutine in the queue for the specified signal. Subroutines are
called in the order that they're added to the queue. Adding a specific subroutine more
than once is filtered out so each subroutine in the queue is unique.
uninstallSIGH
uninstallSIGH($signal, &subroutine);
Removes a subroutine from the specified queue.
installSIGD
installSIGD();
Inserts the dispatcher for each signal with subroutines in the queue.
uninstallSIGD
uninstallSIGD();
Removes the dispatcher for each signal that's using the dispatcher. The signal handler
installed is what ever was set when this module's code was loaded and initialized.
DEPENDENCIES
o Carp
o Paranoid
o Paranoid::Debug
o POSIX
EXAMPLES
pfork
This following example caps the number of children processes to three at a time:
$SIG{CHLD} = \&sigchld;
MAXCHILDREN = 3;
for (1 .. 5) {
# Only the children execute the following block
unless ($pid = pfork()) {
# ....
exit 0;
}
}
You can also install a child-exit routine to be called by sigchld. For instance, to track
the children's history in the parent:
sub recordChild ($$) {
my ($cpid, $cexit) = @_;
push(@chistory, [$cpid, $cexit]);
}
installChldHandler(&recordChild);
for (1 .. 5) {
unless ($pid = pfork()) {
# ....
exit $rv;
}
}
# Prints the child process history
foreach (@chistory) { print "PID: $$_[0] EXIT: $$_[1]\n" };
BUGS AND LIMITATIONS
On Solaris pcapture doesn't return a -1 for non-existant commands, but a 0. On Linux this
appears to work as intended.
AUTHOR
Arthur Corliss (corliss@digitalmages.com)
LICENSE AND COPYRIGHT
This software is licensed under the same terms as Perl, itself. Please see
http://dev.perl.org/licenses/ for more information.
(c) 2005 - 2017, Arthur Corliss (corliss@digitalmages.com)