CODEWITHSUNDEEP
regexperl
Brian G.
Brian G.

Reputation: 13

Perl check for input, otherwise use default

I would like Perl to check the command line to see if there were input files/arguments. Otherwise, use the default file when there are no arguments:

#!/usr/bin/perl -w

open(INPUT, "<", "./list2") || die "Couldn't open list for reading: $!\n";

while (<INPUT>)
{
  # print stuff;
}
close(INPUT);

I've got the default file (list2) that will be opened, but don't know how to check for input. I'm thinking of using a conditional statement (if argument_exists then read the input from the command line; else open the default_file). Does this exist in a library in Perl, or is there a regular expression ?

Upvotes: 1

Views: 535

Answers (2)

Shawn Darichuk
Shawn Darichuk

Reputation: 390

Since you're trying to read the file, it might make sense to check if the command line argument file exists. You can also make sure the argument is a file, not a socket or some other weird thing you're not expecting.

my @temp_array = @ARGV;         #make a copy of command line arguments
@ARGV = ();                     #we will re-build this list
foreach (@temp_array) {         #check the validity of every argument
    if (-e and -f) {            #-e means the path exists, -f means it's a file
        push @ARGV, $_;         #add this back to the @ARV list
    } else {
        print "Path '$_' is invalid\n";
    } #/else
} #/foreach

if (!@ARGV) {
    push @ARGV, './list2';
}

Upvotes: 0

Miller
Miller

Reputation: 35208

Parameters to your script are held in @ARGV. Therefore, simply check if that array contains any values, and add your desired logic.

You can also use @ARGV for reading from your default file like so:

#!/usr/bin/perl -w
use strict;
use warnings;

@ARGV = './list2' if ! @ARGV;

while (<>) {
    # print stuff
}

Upvotes: 4

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