Perl – Capture the output of Perl’s ‘system()’

perlshell

I need to run a shell command with system() in Perl. For example,

system('ls')

The system call will print to STDOUT, but I want to capture the output into a variable so that I can do future processing with my Perl code.

Best Answer

That's what backticks are for. From perldoc perlfaq8:

Why can't I get the output of a command with system()?

You're confusing the purpose of system() and backticks (``). system() runs a command and returns exit status information (as a 16 bit value: the low 7 bits are the signal the process died from, if any, and the high 8 bits are the actual exit value). Backticks (``) run a command and return what it sent to STDOUT.
my $exit_status   = system("mail-users");
my $output_string = `ls`;

See perldoc perlop for more details.

Related Solutions

Python – How to execute a program or call a system command

Use the subprocess module in the standard library:

import subprocess
subprocess.run(["ls", "-l"])

The advantage of subprocess.run over os.system is that it is more flexible (you can get the stdout, stderr, the "real" status code, better error handling, etc...).

Even the documentation for os.system recommends using subprocess instead:

The subprocess module provides more powerful facilities for spawning new processes and retrieving their results; using that module is preferable to using this function. See the Replacing Older Functions with the subprocess Module section in the subprocess documentation for some helpful recipes.

On Python 3.4 and earlier, use subprocess.call instead of .run:

subprocess.call(["ls", "-l"])

How to use SSH to run a local shell script on a remote machine

If Machine A is a Windows box, you can use Plink (part of PuTTY) with the -m parameter, and it will execute the local script on the remote server.

plink root@MachineB -m local_script.sh

If Machine A is a Unix-based system, you can use:

ssh root@MachineB 'bash -s' < local_script.sh

You shouldn't have to copy the script to the remote server to run it.

Best Answer

Related Solutions

Python – How to execute a program or call a system command

How to use SSH to run a local shell script on a remote machine

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