Re: kill process when file count reached,,.

On Jul 2, 6:10 am, Leon Timmermans <faw...@xxxxxxxxx> wrote:
On Tue, 01 Jul 2008 16:25:44 -0700, onlineviewer wrote:
Hello All,

I am trying to run a tcpdump and have perl kill the tcpdump once 10
files have been created by tcpdump. Here is my code, not sure if my
logic is screwy
Thanks,

Hi,

I think this should have been posted at comp.lang.perl.misc instead of
here. Please think of that next time.

#!/usr/bin/perl

Please use strict and warnings, specially when asking for help. It
prevents a lot of bugs.

system "tcpdump -i bge1 -s0 -w /tmp/file.out -C 1"; sleep 2;

From the documentation of system():
"Does exactly the same thing as "exec LIST", except that a fork is done
first, and the *parent process waits for the child process to complete*."
That's not going to work.

while(true){

true? This is perl, not a shell script. Also, you might want to move that
sleep into the loop, or else it will burn CPU time. Also, you're having
an infinite loop there, which you probably don't want.

@array1 = `ls -l /tmp | grep files`;

IMO you could just use readdir and grep in perl. That should be strongly
preferred over using backticks (alternatively you could use File::Find,
but I'd say that's an overkill in this case). Further the names don't
match ('file.out' vs 'files'), which is definitely a bug. Also please
don't call your array @array1, it's probably the worst possible name you
could give it.

$result=@array1+1;

What does the +1 serve for??

if ($result > 3){

In your text you talk about 10 files, but this only checks for 2? Why?

$x=`ps -ef | awk '/tcpdump/ && !/awk/ {print
$2}'`;

You're using awk in backticks in a perl script? Make a choice: shell
scripting or perl scripting. Also, there is a pidof program you could
have used, but a better approach would have been to use fork & exec, in
that case you wouldn't have had this problem in the first place.

@y=split(' ', $x);
$c=$y[1];

This looks a bit double and broken...

system "kill -9 $c";

Perl has a kill builtin, why the hell not use that. Also, is a -9 really
necessary?

print "killing tcpdump...";
}else{
print "!!!\n";
exit;

If there are fewer than 3 files, it exits, if there are more, it will go
into infinite loop. That's got to be an error.

How about this program?

#!/usr/bin/perl

use strict;
use warnings;

defined(my $pid = fork) or die "Couldn't fork: $!\n";
if ($pid) {
while (1) {
sleep 2;
opendir my $dir, "/tmp" or die "Couldn't open /tmp: $!\n";
my @files = grep { /file.out/ } readdir $dir;
closedir $dir;
if (@files >= 10) {
print "killing tcpdump...\n";
kill 'TERM', $pid;
last;
}
else {
print "!!!\n";
}
}}

else {
else exec 'tcpdump -i bge1 -s0 -w /tmp/file.out -C 1';

}

In case someone might forget, the parent'll need
a 'wait' or 'waitpid' too.

A quick 'n dirty alternative although I'm still
not sure how the multiple output files are
named:

system("tcpdump... &");
sleep 2 while (()=glob("/tmp/...")) < 10;
kill 'TERM', -$$;

--
Charles DeRykus

.

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