Running operating system commands in Perl

Archive - Originally posted on "The Horse's Mouth" - 2008-07-08 18:37:03 - Graham Ellis
Perl is excellent "glueware" - a language which can be well used to connect together a whole lot of elements. And one of those elements may be operating system commands run from within the Perl program.

Here are (three!) ways that you can do it - in each case leaving the result of running the commands in a scalar variable.

# CAUTION - OS Dependent!

 

$imc = `uname -m`;

 

$imd = qx!uname -r!;

 

$imcalled = <<`DONE`

uname -s

date

uptime

DONE

;

 

# CAUTION - OS Dependent!

 

print ("***** Here document:\n$imcalled\n");

print ("***** Backquote:\n$imc\n");

print ("***** qx:\n$imd");

So that's
* A text string of commands in backquotes
* A text string of commands in a 'qx' string
* A text block (here document)

And here's how it runs:

BirthdayBoy:csr1 grahamellis$ perl bq

***** Here document:

Darwin

Tue  8 Jul 2008 18:41:38 BST

18:41  up 31 mins, 2 users, load averages: 0.01 0.05 0.06

 

***** Backquote:

Power Macintosh

 

***** qx:

9.0.0

BirthdayBoy:csr1 grahamellis$

You can also run operating system commands via a piped file handle, where you'll read back the response line by line:

open (FH,"ls -l *.*|");

while ($line = <FH>) {

  print ++$n," ",$line;

  }

Which gives us ...

BirthdayBoy:csr1 grahamellis$ perl lbl

1 -rw-r--r--  1 grahamellis  grahamellis  2856  7 Jul 16:35 dis.txt

2 -rw-r--r--  1 grahamellis  grahamellis   825  8 Jul 09:24 fred.txt

3 -rw-r--r--  1 grahamellis  grahamellis     3  7 Jul 10:04 pod2htmd.tmp

4 -rw-r--r--  1 grahamellis  grahamellis     3  7 Jul 10:04 pod2htmi.tmp

5 -rw-r--r--  1 grahamellis  grahamellis   502  8 Jul 14:28 tick.pm

BirthdayBoy:csr1 grahamellis$

(By the way - the name of my computer today - "BirthdayBoy" - has been allocated to me by the router at the hotel and does not imply anything about the day I was born!)

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Running operating system commands in Perl