Hi Nora,
On Thursday 24 Jun 2010 10:15:11 HACKER Nora wrote:
> Hi list,
>
> I am currently having an issue with background processes. I already
> searched the web and found a way how to principally send a process into
> background, wait for the execution to finish and then go on with the
> main program:
>
> my $pid = fork;
> if ( $pid ) {
> wait;
> print "done.\n";
> } else {
> print "starting.\n";
> system "compress *.dbf &";
> exit;
> }
>
> The "done." is being issued at the correct point of time, namely when
> really all files have been compressed. Unfortunately, this only
> compresses one file after the other and therefore lacks performance. So
> I tried to send multiple processes into background and have them to be
> executed simultaneously. I tried the following:
>
> my $pid = fork;
> if ( $pid ) {
> wait;
> print "done.\n";
> } else {
> print "starting.\n";
> foreach ( glob "*.dbf" ) {
> system "compress $_ &";
> exit;
> }
>
> This behaves as expected, from the "simultaneous" and "background" point
> of view - but my big problem is now that the message "done." is being
> issued as soon as all the compression processes are ISSUED instead of
> when they are FINISHED.
>
> Could anybody please point me into the right direction how to best solve
> that issue? Maybe I should fork all the single compression processes to
> get a pid for each, put them into an array and check with a loop whether
> they still exist (process running)? Would there be another / easier /
> more efficient way?
>
Look into http://perldoc.perl.org/functions/wait.html and
http://perldoc.perl.org/functions/waitpid.html .
Regards,
Shlomi Fish
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