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

user_113124 0
Viewed 126137
$ 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
$

I want to capture the result i.e. 11 into a variable. How can I do that?

command system perl
6 Answers

Try using qx{command} rather than backticks. To me, it's a bit better because: you can do SQL with it and not worry about escaping quotes and such. Depending on the editor and screen, my old eyes tend to miss the tiny back ticks, and it shouldn't ever have an issue with being overloaded like using angle brackets versus glob.

user_12891270

Use backticks for system commands, which helps to store their results into Perl variables.

my $pid = 5892;
my $not = ``top -H -p $pid -n 1 | grep myprocess | wc -l`; 
print "not = $not\n";
user_107821760

Also for eg. you can use IPC::Run:

use IPC::Run qw(run);

my $pid = 5892;
run [qw(top -H -n 1 -p), $pid],
    '|', sub { print grep { /myprocess/ } <STDIN> },
    '|', [qw(wc -l)],
    '>', \my $out;

print $out;
  • processes are running without bash subprocess
  • can be piped to perl subs
  • very similar to shell
user_3317030
Related