How to force a timeout on a system call?

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

I have a Perl script called by crontab once a day.
Within this script I make a system call to whois. Such as:

#!/usr/bin/perl -wT
use strict;

## [snipped for brevity]

my $resultin = `whois $dom`;
[download]

Every now and then I'll take a peek at the current processes using "ps -aux" and I'll notice a stuck "whois" running along with a script waiting its output.

I'm sure there is a simple strategy to wrap this system call so that I can either kill it or at least move on.

Any clues would be appreciated.

Claude

Comment on How to force a timeout on a system call? Download Code

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Re: How to force a timeout on a system call? by maverick (Curate) on Jun 21, 2001 at 23:56 UTC
Try this. `eval { local $SIG{'ALRM'} = sub { die "timed out\n" }; alarm(10); system("sleep 30; echo 'I made it'") && die "system call faile +d\n"; alarm(0); }; if ($@) { if ($@ eq "timed out\n") { print "I timed out\n"; } else { print "something else went boom\n"; } } else { print "I didn't time out\n"; }` [download] In ten seconds you should get output that reads "I timed out". This is almost exactly the eval timeout out example from the 'perlfunc' perldoc page. I modified it a little to have print statements for what happened where. /\/\averick Updated: bluto is quite right. here is my updated code. This seems to work fine under Linux. The only problem I have with Dominus solution is requiring the external program (you should be able to get it to work in one piece of code IMHO ;) ) `-- first.pl -- #!/usr/bin/perl use strict; my $pid; eval { local $SIG{'ALRM'} = sub { die "timed out\n" }; alarm(10); $pid = fork; if ($pid == 0) { exec("./second.pl"); } else { wait; } alarm(0); }; if ($@) { if ($@ eq "timed out\n") { kill(15,$pid); print "I timed out\n"; } else { print "something else went boom\n"; } } else { print "I didn't time out\n"; } -- second.pl -- #!/usr/bin/perl while(1) { print "alive\n"; sleep(1); }` [download] This produces this output on my system. `darkstar:~>./first.pl alive alive alive alive alive alive alive alive alive alive I timed out darkstar:~>` [download]	[reply] [d/l] [select]
Re: Re: How to force a timeout on a system call? by Xxaxx (Monk) on Jun 23, 2001 at 14:06 UTC
Much thanks for the update. Claude	[reply]
Re^2: How to force a timeout on a system call? by Freezer (Sexton) on Aug 17, 2012 at 17:40 UTC
It doesn't do that on my system : `I didn't time out I didn't time out` [download]	[reply] [d/l]
Re: How to force a timeout on a system call? by bluto (Curate) on Jun 22, 2001 at 01:19 UTC
The eval/alarm solution does not kill the child generated by system(). See the discussion at: Timing out shell commands (paranoia), esp Dominus's reply. -- bluto	[reply]
Re: How to force a timeout on a system call? by tarjema (Initiate) on Jun 22, 2001 at 03:26 UTC
I'd actually eliminate the problem sideways and use Net::XWhois: `use Net::XWhois; my $whois = new Net::XWhois DOMAIN => $domain;` [download] Then do whatever you're after on the response. To get the name servers: `@nservers = $whois->nameservers()` --tarjema	[reply] [d/l] [select]