CODEWITHSUNDEEP
perlunixrhel
Prashant Shete
Prashant Shete

Reputation: 60

how to specify arguments to unix command in perl

I am trying to find the processes which are not running through perl. It works for some processes using following code but not for cgred service. 

foreach $critproc (@critarray)
    {
    #system("/usr/bin/pgrep $critproc");
    $var1=`/usr/bin/pgrep $critproc`;
    print "$var1";
    print "exit status: $?\n:$critproc\n";
    if ($? != 0)
            {
            $probs="$probs $critproc,";
            $proccrit=1;
            }
    }

For cgred I have to specify /usr/bin/pgrep -f cgred to check whether any pid is associated with it or not. But when I specify -f in above code it gives exit status 0 ($?) to all the processes even if its not running.

Can you anyone tell me how to pass arguments to unix command in Perl.

Thanks

Upvotes: 0

Views: 55

Answers (1)

ikegami
ikegami

Reputation: 386461

What's $critproc? Where's the -f you say is giving you problems? One might imagine you have some kind of escaping problem, but that shouldn't be the case if $critproc is cgred as you seem to imply.

Given these problem, I'm just going to answer the general question.

The following avoids the shell, so no need to build a shell command:

system("/usr/bin/pgrep", "-f", $critproc);
die "Killed by signal ".( $? & 0x7F ) if $? & 0x7F;
die "Exited with error ".( $? >> 8 ) if ($? >> 8) > 1;
my $found = !($? >> 8);

If you need a shell command, you can use String::ShellQuote's shell_quote to build it.

use String::ShellQuote qw( shell_quote );

my $shell_cmd = shell_quote("/usr/bin/pgrep", "-f", $critproc) . " >/dev/null";
system($shell_cmd);
die "Killed by signal ".( $? & 0x7F ) if $? & 0x7F;
die "Exited with error ".( $? >> 8 ) if ($? >> 8) > 1;
my $found = !($? >> 8);

or

use String::ShellQuote qw( shell_quote );

my $shell_cmd = shell_quote("/usr/bin/pgrep", "-f", $critproc);
my $pid = `$shell_cmd`;
die "Killed by signal ".( $? & 0x7F ) if $? & 0x7F;
die "Exited with error ".( $? >> 8 ) if ($? >> 8) > 1;
my $found = !($? >> 8);

Upvotes: 4

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