How can I store the result of a system command in a Perl variable?

Question

$ cat test.pl
my $pid = 5892;
my $not = system(\"top -H -p $pid -n 1 | grep myprocess | wc -l\");
print \"not = $not\\n\";
$ perl test.pl
11
not = 0
$

Answer 1

The easiest way is to use the `` feature in Perl. This will execute what is inside and return what was printed to stdout:

 my $pid = 5892;
 my $var = `top -H -p $pid -n 1 | grep myprocess | wc -l`;
 print "not = $var\n";

This should do it.