Reaper(3) User Contributed Perl Documentation Reaper(3)NAMEReaper - support for reaping child processes via $SIG{CHLD}
SYNOPSIS
use Reaper qw( reaper reapPid pidStatus );
my $pid = fork;
if ( $pid == 0 ) { # child
exec $some_command;
}
reapPid ( $pid );
...
if ( defined(my $exit = pidStatus($pid)) ) {
# child exited, check the code...
}
DESCRIPTION
perl has an annoying little problem with child processes -- well, it is
not actually a problem specific to perl, but it is somewhat more
difficult with perl: reaping child processes after they exit so they
don't hang around as zombies forever, and doing it in a way that
accurately captures the exit code of the child.
The right way to do it is to install a $SIG{CHLD} handler which calls
waitpid to reap the child process and store $? at that point. But the
problem is that different modules may step on each other in installing
their own version of the handler, there's no uniform way of doing this.
For some situations, a local $SIG{CHLD} handler is sufficient, but
often times the handler is no longer in scope at the time the child
process exits -- since the child may exit at any time. The local
handler is dynamically scoped, not lexically, so it depends entirely on
what subroutine is being executed at the time the signal is caught.
So the Reaper module provides a $SIG{CHLD} handler that can be
installed globally as well as locally. It also supports chaining of
signal handlers, meaning it will not just replace an existing
$SIG{CHLD} handler. It still requires applications to do the right
thing in using this module and not installing their own versions. At
least it provides a consistent implementation that can be shared
between various modules.
FUNCTIONS IN DETAIL
* reaper BLOCK
Install a local $SIG{CHLD} handler for a block of code, e.g.:
reaper {
do_something();
...
};
Any children that exit while the block is being executed (whether
started within that block or not) will cause the local $SIG{CHLD}
to be executed. The child exit status will be saved, and will be
available via the pidStatus() call.
* reapPid PIDLIST
Register one or more PIDs to be reaped. The reaper will only try
to reap PIDs that have been registered, so that it does not steal
the exit status for a pid from another handler.
* pidStatus PID
Return the exit status of a specific PID. If no status for the PID
is available (i.e. the process is still running), returns undef.
AUTHOR
Jeremy Slade <jeremy@jkslade.net>
POD ERRORS
Hey! The above document had some coding errors, which are explained
below:
Around line 55:
You can't have =items (as at line 151) unless the first thing after
the =over is an =item
perl v5.14.0 2006-06-07 Reaper(3)
