Processing Command Line Arguments

When a Perl script is run, its command-line arguments (if any) are stored in an automatic array called @ARGV. You'll learn how to manipulate this array later. For now, just know that you can call the shift function repeatedly from the main part of the script to retrieve the command line arguments one by one.

Printing the Command Line Argument

Code:

  
  #!/usr/bin/perl
  # file: echo.pl

  $argument = shift;
  print "The first argument was $argument.\n";

Output:

(~) 50% chmod +x echo.pl
(~) 51% echo.pl tuna
The first argument was tuna.
(~) 52% echo.pl tuna fish
The first argument was tuna.
(~) 53% echo.pl 'tuna fish'
The first argument was tuna fish.
(~) 53% echo.pl
The first argument was .

Computing the Hypotenuse of a Right Triangle

Code:

  
  #!/usr/bin/perl
  # file: hypotenuse.pl

  $x = shift;
  $y = shift;
  $x>0 and $y>0 or die "Must provide two positive numbers";
  
  print "Hypotenuse=",sqrt($x**2+$y**2),"\n";

Output:

(~) 82% hypotenuse.pl
Must provide two positive numbers at hypotenuse.pl line 6.
(~) 83% hypotenuse.pl 1
Must provide two positive numbers at hypotenuse.pl line 6.
(~) 84% hypotenuse.pl 3 4
Hypotenuse=5
(~) 85% hypotenuse.pl 20 18
Hypotenuse=26.9072480941474
(~) 86% hypotenuse.pl -20 18
Must provide two positive numbers at hypotenuse.pl line 6.

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