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Postings from August 2001
The example code for waitpid in perlfunc recommends the &WNOHANG
construct. In certain cases, this can cause a spurious and curious
warning message in the POSIX module.
For example:
use POSIX;
$SIG{CHLD} = sub {
warn "@_";
my $process_id = waitpid(-1,&WNOHANG); warn "Reaped $process_id!";
};
defined(my $pid = fork()) or die;
if ($pid) {
warn "Launched $pid!";
sleep 1;
}
producing:
Argument "CHLD" isn't numeric in entersub at
/usr/lib/perl5/5.00503/i386-linux/POSIX.pm line 207.
Removing the ampersand from WNOHANG avoids the warning. (It does not
silently pass along the contents of @_).
The following patches against 5.7.2 update the documentation to recommend
a bareword call (already used in perlipc). In addition, one core module
used the dodgy semantics.
--- ext/POSIX/~POSIX.pod Mon Aug 27 11:06:33 2001 +++ ext/POSIX/POSIX.pod
Mon Aug 27 11:06:50 2001 @@ -1535,7 +1535,7 @@
Wait for a child process to change state. This is identical to Perl's
builtin C<waitpid()> function, see L<perlfunc/waitpid>.
- $pid = POSIX::waitpid( -1, &POSIX::WNOHANG );
+ $pid = POSIX::waitpid( -1, POSIX::WNOHANG );
print "status = ", ($? / 256), "\n";
=item wcstombs
--- pod/~perlfunc.pod Mon Aug 27 10:56:12 2001 +++ pod/perlfunc.pod Mon
Aug 27 10:56:26 2001 @@ -5915,7 +5915,7 @@
use POSIX ":sys_wait_h";
#...
do {
- $kid = waitpid(-1,&WNOHANG);
+ $kid = waitpid(-1,WNOHANG);
} until $kid == -1;
then you can do a non-blocking wait for all pending zombie processes.
--- lib/Net/~Ping.pm Mon Aug 27 11:00:38 2001 +++ lib/Net/Ping.pm Mon Aug
27 11:00:48 2001 @@ -353,7 +353,7 @@
# Wait for the child to return or for the timeout to expire. do {
- $child = waitpid($pid, &WNOHANG);
+ $child = waitpid($pid, WNOHANG);
$ret = $?;
} until time > ($time + $timeout) or $child;
-- c
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