Get a variable from an array in perl - linux

Question

I am running a following command and getting the 4 lines as output.
userid#server:/home/userid# ps -ef|grep process
This is the output for the command.
userid 10117 9931 0 06:25 pts/0 00:00:00 grep process
userid 15329 1 0 Jul11 ? 00:03:40 process APP1
userid 15334 15329 1 Jul11 ? 2-00:40:53 process1 APP1
userid 15390 15334 0 Jul11 ? 05:19:31 process2 APP1
I want to save the value APP1 to a variable using perl. So I want an output like $APP = APP1.

Answer 1

Try this (your output is in this case in the file in.txt):
perl -ne ' /(APP\d+)/g; print "$1\n";' in.txt
Prints:
APP1
APP1
APP1

Answer 2

Perhaps using an array for the captured APPS1s would be helpful:
use strict;
use warnings;
my #apps;
while (<DATA>) {
push #apps, $1 if /process\d*\s+(.+)/;
}
print "$_\n" for #apps;
__DATA__
userid 10117 9931 0 06:25 pts/0 00:00:00 grep process
userid 15329 1 0 Jul11 ? 00:03:40 process APP1
userid 15334 15329 1 Jul11 ? 2-00:40:53 process1 APP1
userid 15390 15334 0 Jul11 ? 05:19:31 process2 APP1
Output:
APP1
APP1
APP1

Answer 3

Is APP1 the last entry on the command line? Or, is it the second word after the process* command?
If it's the last word on the line, you could use this:
use strict;
use warnings;
use autodie;
open my $command_output, "|-", "pgrep -fl process";
while ( my $command = < $command_output > ) {
$command =~ /(\w+)$/;
my $app = $1; #The last word on the line...
Otherwise, things get a bit more tricky. I am using pgrep instead of ps -ef | grep. The ps command returns a header, plus lots of fields. You need to split them, and parse them all. Plus, it even shows you the grep command you used to get the processes you're interested in.
The pgrep command with the -f and -l parameters returns no header and returns just the process ID followed by the full command. This makes it much easier to parse with a regular expression. (If you don't know about regular expressions, you need to learn about them.)
open my $command_output, "|-", "pgrep -fl process";
while ( my $command = < $command_output > ) {
if ( not $process =~ /^\d+\s+process\w+\s+(\w+)/ ) {
next;
}
my $app = $1; #The second word in the returned command...
There's no need to split or mess. There's no header to skip The regular expression matches the numeric process ID, the process command, and then selects the second word. I even check to make sure the output of the pgrep matches what I expect. Otherwise, I'll get the next line.

Answer 4

I used a single line command to get the required result.
#!/usr/bin/perl
use strict;
use warnings;
my $app1
$app1 = ( split /\s+/, `pgrep -f process1` )[-1];
print ($app1);