Portable Process Control

scmason has asked for the wisdom of the Perl Monks concerning the following question:

Greetings Monks, I know that this is a silly question, but we are pressed for time and I wanted to draw on your experience. So here are the details:

We are writing a test script as part of a porting effort. We need to perform the following:

Open a program and
1. read its STDOUT
2. calculate its system time
3. calculate its max memory
4. kill it if the script is Control-C'd

Here are the caveats: it has to be Unix/Win portable and can not use any non-core modules.

So, we use open(PROG,"pogname|") to open the program with a handle to its stdout. We install a signal-handler to deal with keyboard interupts. Fine. But how do we kill a program started by 'open' from the signal handler? Simply closing the filehandle is not enough.

To get the system time, we use 'times' as such:

($user,$system,$cuser,$csystem) = times;

It seems to me that the program started with 'open' should be our child, but $cuser & $csystem are zero. Does this only work when you have forked a child?

As for the max memory issue, I could scan the ps table, but this is not portable. I am at a loss here.

I know that this is actually several questions. I am also painfully aware that there is no easy answer, but I will be happy to consider any advise you might have to offer.

"Never take yourself too seriously, because everyone knows that fat birds dont fly" -FLC

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Re: Portable Process Control by ikegami (Patriarch) on Aug 24, 2005 at 17:45 UTC
Calculating a child/program's memory usage is not possible when using only core modules. Calculating a child/program's memory usage is not portable. You'd have to branch based on `$^O`. I'm not sure about the others.	[reply] [d/l]
Re: Portable Process Control by MidLifeXis (Monsignor) on Aug 24, 2005 at 17:39 UTC
But how do we kill a program started by 'open' from the signal handler? From `perldoc -f open` Open returns nonzero upon success, the undefined value otherwise. If the "open" involved a pipe, the return value happens to be the pid of the subprocess. --MidLifeXis	[reply] [d/l]
Re: Portable Process Control by sk (Curate) on Aug 24, 2005 at 17:54 UTC
This progam starts another prog and reads from its STDOUT. The other prog just prints hi there in an infinite loop. `#!/usr/bin/perl -w open (PIPE,"printsth \|") or die $!; while(<PIPE>) {print; last if $i++ >=1000; } close(PIPE) or die "Quit with exit status: $? message: $!" ;` [download] `#prog printsth #!/usr/bin/perl -w print "hi there", $/ while(1);` [download] When i run my first scirpt it (`close`) terminates the pipe but fails for some reason. However i don't see my program opened through the script running in the system so it has been forced to terminate somehow `hi there .... .... hi there hi there Quit with exit status: 13 message: at termpipe line 7.` [download]	[reply] [d/l] [select]