in reply to SIGCHLD and return codes

From perlipc:
On most Unix platforms, the `CHLD' (sometimes also known as `CLD') signal has special behavior with respect to a value of `'IGNORE''. Setting `$SIG{CHLD}' to `'IGNORE'' on such a platform has the effect of not creating zombie processes when the parent process fails to `wait()' on its child processes (i.e. child processes are automatically reaped). Calling `wait()' with `$SIG{CHLD}' set to `'IGNORE'' usually returns `-1' on such platforms.
I would install a signal handler that calls wait to reap the child process and get its exit status, as in this excerpt, adapted from perlipc: 
sub REAPER {
  $waitedpid = wait;

  # now status is in $?
  print "reaped pid $waitedpid, exited with status ", $? >> 8, "\n";

  # loathe sysV: it makes us not only reinstate
  # the handler, but place it after the wait
  $SIG{CHLD} = \&REAPER;
}
$SIG{CHLD} = \&REAPER;

[download]


--sacked

Replies are listed 'Best First'.
Re: (sacked) Re: SIGCHLD and return codes
by shrubbery (Acolyte) on Nov 17, 2001 at 00:30 UTC
    Looks like that works but how do I return $? from the handler?
[reply]
      Use a hash: 
      # once again, adapted from perlipc

use vars qw( %status ); # our, if you prefer

sub REAPER {
  $waitedpid = wait;

  # now status is in $?
  $status{ $waitedpid } = $? >> 8;

  # loathe sysV: it makes us not only reinstate
  # the handler, but place it after the wait
  $SIG{CHLD} = \&REAPER;
}
$SIG{CHLD} = \&REAPER;

while ( my ($k,$v) = each %status ) {
  print "pid $k\tstatus $v\n"
}

      [download]

      --sacked
[reply]
[d/l]

In Section Seekers of Perl Wisdom