How can I pass command-line arguments to a Perl program?

Question

I'm working on a Perl script. First time in more than a decade. Really.

How can I pass command line parameters to it?

Example:

script.pl "string1" "string2"

Answer 1

You pass them in just like you're thinking, and in your script, you get them from the array @ARGV. Like so:

$numArgs = $#ARGV + 1;
print "thanks, you gave me $numArgs command-line arguments.\n";

foreach $argnum (0 .. $#ARGV) {

   print "$ARGV[$argnum]\n";

}

From here.

Answer 2

foreach my $arg (@ARGV) {
    print $arg, "\n";
}

will print each argument.

Answer 3

Depends on what you want to do. If you want to use the two arguments as input files, you can just pass them in and then use <> to read their contents.

If they have a different meaning, you can use GetOpt::Std and GetOpt::Long to process them easily. GetOpt::Std supports only single-character switches and GetOpt::Long is much more flexible. From GetOpt::Long:

use Getopt::Long;
my $data   = "file.dat";
my $length = 24;
my $verbose;
$result = GetOptions ("length=i" => \$length,    # numeric
                    "file=s"   => \$data,      # string
                    "verbose"  => \$verbose);  # flag

Alternatively, @ARGV is a special variable that contains all the command line arguments. $ARGV[0] is the first (ie. "string1" in your case) and $ARGV[1] is the second argument. You don't need a special module to access @ARGV.

Answer 4

If the arguments are filenames to be read from, use the diamond (<>) operator to get at their contents:

while (my $line = <>) {
  process_line($line);
}

If the arguments are options/switches, use GetOpt::Std or GetOpt::Long, as already shown by slavy13.myopenid.com.

On the off chance that they're something else, you can access them either by walking through @ARGV explicitly or with the shift command:

while (my $arg = shift) {
  print "Found argument $arg\n";
}

(Note that doing this with shift will only work if you are outside of all subs. Within a sub, it will retrieve the list of arguments passed to the sub rather than those passed to the program.)

Answer 5

If you just want some values, you can just use the @ARGV array. But if you are looking for something more powerful in order to do some command line options processing, you should use Getopt::Long.

Answer 6

Funny, I forgot to specify the datatype using Getopt (passing an integer, '=i') and the result was that a 0 became a 1, but a 1 remained a 1 and a 2 a 2 and so on.

Cheers