Front page | perl.perl5.porters |
Postings from August 2005
On Mon, Aug 22, 2005 at 03:29:42AM -0700, Chris wrote:
>
> Calls to system() in a forked child always return -1 if the parent has
> set SIG{CHLD}='IGNORE'. I would expect/hope it to return 0.
>
> Demonstrated by:
> perl -e '$SIG{CHLD} = "IGNORE"; fork or sleep 0xbeef; print
> "system:".system("true")."\n";'
> prints: system:-1
When $SIG{CHLD} is set to "IGNORE", wait(2) will return -1 [1]. Since
system returns the status as provided by wait and wait isn't providing a
status I think the -1 return is reasonable. Check $! when system
returns -1; in this case it will say "No child processes" (ECHILD).
The patch after my .sig addresses this in perlfunc.
[1] On Linux this is not true and wait(2) will ignore the IGNORE and
actually wait for the process to finish, returning the status and
pid. I personally don't think perl should support this behaviour.
--
Rick Delaney
rick@bort.ca
diff -ruN perl-current/pod/perlfunc.pod perl-current-dev/pod/perlfunc.pod
--- perl-current/pod/perlfunc.pod 2005-08-05 10:42:09.000000000 -0400
+++ perl-current-dev/pod/perlfunc.pod 2005-08-22 13:19:01.312460976 -0400
@@ -6017,6 +6017,8 @@
the output from a command, for that you should use merely backticks or
C<qx//>, as described in L<perlop/"`STRING`">. Return value of -1
indicates a failure to start the program (inspect $! for the reason).
+It could also mean that you have set C< $SIG{CHLD} = 'IGNORE' >, in which
+case the C<wait> call would return -1 (inspect $!).
Like C<exec>, C<system> allows you to lie to a program about its name if
you use the C<system PROGRAM LIST> syntax. Again, see L</exec>.
Thread Previous
|
Thread Next