how to store values from system command

[veeruch]

hi perlmonks,
if i give a code like given below ,i couldn't get the $val how can i get it the values;

/usr/bin/perl -w
use strict;
my $val = system("ls -lrt ");
print "$val";

[ikegami]

When you want to capture output, use backticks

my $val = `ls -lrt`;

or

my $val = qx/ls -lrt/;

Ref: perlop

[andyford]

Please ignore this post if you really really want the output of 'ls',
but if you're doing what I think you're doing, take a step back and check out the documention for the internal Perl ways of doing things.
This will allow you to build a robust, portable, and maintainable application.

reading directories

getting the properties of files

[swampyankee]

In your sample, $val will contain the return code from ls. Most system commands return 0 or undef on success, so your system("ls -lrt "); call is succeeding (I'm quite sure ls can fail; I just can't remember seeing it do so.).

As ikegami and andyford mentioned, using system is almost certainly not the best solution. For one thing, it uses a sub-shell, where using glob or opendir doesn't.

You could try something like this (see stat):

#!perl

use strict;

use warnings;

my @list = glob("*");

foreach(@list){

    (my $dev,   my $ino,     my $mode, my $nlink, my $uid,
     my $gid,   my $rdev,    my $size, my $atime, my $mtime,
     my $ctime, my $blksize, my $blocks) = stat;

     # do processing here

}

yeah, verily, an update

ikegami pointed out that system only uses a subshell if the command contains shell metacharacters. In any case, unless you need the data exactly as produced by ls, using the Perl functions is certainly more portable (Windows doesn't have ls), and possibly faster.

---

[ikegami]

$val will contain the return code from ls.

[system] uses a sub-shell

One of those statments is necessarily false. If a shell is used, $val will contain the return value of the shell, not ls.

So does system use a shell? It depends. "If there is only one scalar argument, the argument is checked for shell metacharacters, and if there are any, the entire argument is passed to the system's command shell for parsing." Otherwise, no.

In this case? no. However, I still wouldn't use ls.

Some examples:

system('command foobar')      # no shell
system('command "foo bar"')   # shell
system('command', 'foo bar')  # no shell
system('sort < file | uniq')  # shell