On Feb 15, 12:35 pm, shawnhco...@gmail.com (Shawn H Corey) wrote:
> Matthias Meyer wrote:
> > Hi group,
>
> > I try to catch a signal, write out some statistics about my running
> > perl program and continue afterwards with the program.
>
> > use strict;
> > no utf8;
> > use MyProgram::Lib;
> > use Encode;
> > use Socket;
> > use File::Path;
> > use File::Find;
> > use Getopt::Std;
> > die("MyProgram::Lib->new failed\n") if ( !(my $init = MyProgram::Lib->init)
> > );
> > $SIG{ILL} = \&write_status;
> > :
> > sub write_status
> > {
> > my $sigName = shift;
>
> > print( STDERR "Signal ILL catched" );
> > return;
> > }
> > Within bash I send the signal with "kill -4 <procID>"
> > Unfortunately my program die after catching the signal.
> > Without the print it dies too.
> > Also within debugger (perl -d:ptkdb) it dies after the return statement.
>
> > Is it possible to interrupt a perl program and continue afterwards?
>
> > Thanks
> > Matthias
>
> What OS?
>
> Normally a program continues but if it is waiting or sleeping, it
> continues after the command. You have to redo the command until it
> terminates correctly. Example: waiting for a child process:
>
> my $child_pid = 0;
> WAIT_BLOCK: {
> $child_pid = wait();
> redo WAIT_BLOCK if $child_pid == 0 || $child_pid < -1;
>
> }
>
No, you don't need 'redo' on a blocking wait. I see why you
might conclude that reading the waitpid doc but I believe the
that doc is mis-leading in not clarifying that only a non-blocking
wait, ie, WNOHANG, will potentially return a 0.
See:
http://groups.google.de/group/perl.beginners/browse_thread/thread/71ac675f384a9828
Here're the key parts of that exchange which may look remarkably
familiar :)
> On some systems, a value of 0 indicates that there are processes still
> running.
>> I see that but I suspect Perl's waitpid doc is unintentionally
>> misleading.
>> A quick look at Linux and OpenBSD wait(2) manpages specifies a 0
>> return can occur only with FLAGS set to WNOHANG.
>> OpenBSD: from waitpid(2) manpage:
>> Otherwise, if WNOHANG is specified and there
>> are no stopped or exited children, 0 is returned.
>> Linux:
>> ... if WNOHANG was specified and no child(ren) specified by
pid
>> has yet changed state, then 0 is returned.
> In other words, waitpid can return a value which is not the pid of the
> child you requested. Therefore redo, since it's a foreach loop. This,
> of course, is only true on some systems; it may not be true on yours.
>> If there's a system where a blocking waitpid could return
something
>> other than -1 or the specific pid you waited on, that'd be true.
But,
>> even then, you'd have to be careful that a -1 indicating a reaped
>> process didn't cause an endless loop due to the 'redo'.
--
Charles DeRykus
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