Hi,

I need to add a timeout for external calls, as the external program sometimes never dies (it's a ClearQuest multisite call to the shipping server, that sometimes never ends, but simply hangs).

I have three different ways of forking the call, but none works. I send the one I believe most in...

Code: ( perl ) 

   1. use POSIX ":sys_wait_h";
   2. my $loop      = 1;
   3. $loop           = $ARGV[0] if defined $ARGV[0];
   4. my $timeout = 10;
   5. my $child     = fork();
   6. unless ( $child )  {
   7.     # Child
   8.     exec( "perl count.pl $loop" );
   9.     exit 0;
  10. }
  11.       
  12. sleep( $timeout );
  13. my $kid = waitpid( $child, WNOHANG );
  14. if( $kid != -1 )  {
  15.     print "The child is still running! Kill the process: $child.
+..\n";
  16.     kill( 9, $child );
  17. }
  18. else  {  print "no timeout\n";  }

[download]
The external program count.pl, is simply a program that prints an iterator every second:

Code: ( perl ) 

   1. my $loop     = 1;
   2. my $iterator = 1;
   3. $loop          = $ARGV[0] if defined $ARGV[0];
   4. for( ; $iterator <= $loop ; $iterator++ )  {
   5.     sleep( 1 );
   6.     print "$iterator($$)...\n";
   7. }

[download]
The idea is fine. After ten seconds, the mother process detects that the child process is still running, and tries to kill it.

And here is the strange thing!!!

The $child value (returned from the fork() command), is not the same as the $$ in the child process!!!

That means that the kill command is trying to kill another process (which in this case doesn't exist).

If I open another command tool window, and type in: perl -e "kill( 9, <child pid> )" the child is killed.

Am I doing something wrong?

I tried also:

Code: ( perl ) 

   1. local $SIG{ALRM} = sub { die "alarm\n" };       # NB \n required
   2. alarm 10;
   3. $child_pid = fork();
   4. if( $child_pid )  {
   5.     print "Child_pid = $child_pid\n";
   6.     $pid2 = waitpid( $child_pid, 0 );
   7. }
   8. elsif( $child_pid == 0 )  {
   9.     print "child pid= $$\n";
  10.     exec( "ratlperl count.pl $x" );
  11.     exit( 0 );
  12. }

[download]
I do get an alarm signal after the timeout, but I don't have the correct pid here also. kill() doesn't work.

Any help would be appreciated very much.

Cheers, /Richard

In reply to Problem to add a timeout to external calls on Win32 by webotronics

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