Running a command in Perl

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

Please forgive if this is a stupid question but I'm a bit stuck and wondered if you could help?

I have a perl program that gets information about running processes on a server. I have a command that works on the command line but I can't get it to work in my perl script.

The command that works on the command line is:

ps aux | grep java | perl -e 'while(<STDIN>){if (/-Xmx((\d+)[gG])/) { 
+$mem += $2 } } print "total memory reserved by Java processes: ${mem}
+G\n"'
[download]

Which gives me: total memory reserved by Java processes: 58G

If I post this into my perl script no matter how I tweak it I can't get it to work.

Can you please help?

Comment on Running a command in Perl Download Code

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Re: Running a command in Perl by davido (Cardinal) on Jan 28, 2014 at 16:52 UTC
You didn't mention specifically what you tried, and in what way it fails, so it's hard to diagnose what you're doing wrong. Does this work for you? foreach(`ps aux \| grep java`){ if (/-Xmx((\d+)[gG])/) { $mem += $2 } } print "total memory reserved by Java processes: ${mem}G\n" [download] Dave	[reply] [d/l]
Re: Running a command in Perl by Tux (Canon) on Jan 28, 2014 at 17:37 UTC
Why not use Proc::ProcessTable: `$ cat mem.pl use 5.12.1; use warnings; use Data::Peek; use Proc::ProcessTable; my $s; $s += $_->{size} for grep { $_->cmndline =~ /java/ } @{Proc::ProcessTa +ble->new->table}; say $s; $ perl mem.pl 27656867840` [download] Enjoy, Have FUN! H.Merijn	[reply] [d/l]
Re: Running a command in Perl by Laurent_R (Canon) on Jan 28, 2014 at 19:45 UTC
Launching a Perl one-liner within a shell system command launched itself by another Perl program seems to be poor design. If you really want to call a system command from your Perl script just issue this system command: `ps aux \| grep java` [download] and process the output within your other Perl script with the commands you have in your one-liner. Although the filtering made by the grep shall command could itself be done within the Perl script. And then, of course, there are also some pure Perl solutions using modules.	[reply] [d/l]