Display And Pass Command Line Arguments in Perl

Question

I have the following program "Extract.pl", which opens a file, finds the lines containing "warning....", "info...", "disabling..." then counts and prints the value and number of them. It is working ok.

What I want to do is to create command line arguments for each of the 3 matches - warning, disabling and infos and then run either of them from the command prompt.

Here is the code:

#!/usr/bin/perl

use strict;
use warnings;

my %warnings = ();
my %infos = ();
my %disablings = ();    

open (my $file, '<', 'Warnings.txt') or die $!;                 

while (my $line = <$file>)  {                       

 if($line =~ /^warning ([a-zA-Z0-9]*):/i) {                     
     ++$warnings{$1};                           
}
 if($line =~ /^disabling ([a-zA-Z0-9]*):/i) {                       
     ++$disablings{$1};                         
}
 if($line =~ /^info ([a-zA-Z0-9]*):/i) {                        
     ++$infos{$1};                          
}
}
       close $file;                                     

       foreach my $w (sort {$warnings{$a} <=> $warnings{$b}} keys %warnings) {      
   print $w . ": " . $warnings{$w} . "\n";                  
}
       foreach my $d (sort {$disablings{$a} <=> $disablings{$b}} keys %disablings) {        
   print $d . ": " . $disablings{$d} . "\n";                    
}

       foreach my $i (sort {$infos{$a} <=> $infos{$b}} keys %infos) {   
       print $i . ": " . $infos{$i} . "\n"; 
}

You forgot to ask a question. What have you tried to read command line arguments? How does that fail? With a simple google search I found millions of good reads even on SO, including getopt. — memowe
– memowe, Commented Nov 20, 2012 at 16:35
Yes, I will give it a try. I have been reading about command line arguments a lot today, found some examples, but still can't implement them in my code. I have been learning programming and perl in the last dats and I was just seeking help.Thanks. — TheBlackCorsair
– TheBlackCorsair, Commented Nov 20, 2012 at 16:47
"run either of them from the command prompt." makes no sense. Either what? — ikegami
– ikegami, Commented Nov 20, 2012 at 17:10
well i mean that for example if i type in the command prompt Perl Extract.pl Warning it will display only the "Warning" values and not the "disabling" and "infos" and vice-versa. — TheBlackCorsair
– TheBlackCorsair, Commented Nov 20, 2012 at 17:15
So you "found some examples, but still can't implement them in my code". Why? What's happening? This isn't very helpful. — memowe
– memowe, Commented Nov 20, 2012 at 17:42

mpe · Accepted Answer · 2012-11-20 18:30:55Z

1

The builtin special array @ARGV holds all command line arguments to the script, excluding the script file itself (and the interpreter, if called as perl script.pl). In the case of a call like perl script.pl foo bar warnings, @ARGV would contain the values 'foo', 'bar', and 'warnings'. It's a normal array, so you could write something like (assuming the first argument is one of your options):

my ($warning, $info, $disabling);
if    ($ARGV[0] =~ /warning/i)   { $warning = 1   }
elsif ($ARGV[0] =~ /info/i)      { $info = 1      }
elsif ($ARGV[0] =~ /disabling/i) { $disabling = 1 }

# [...] (opening the file, starting the main loop etc...)

if ( $warning and $line =~ /^warning ([a-zA-Z0-9]*)/i ) {
    ++$warnings{$1};
}
elsif ( $info and $line =~ /^info ([a-zA-Z0-9]*)/i ) {
    ++$infos{$1};
}
elsif ( $disabling and $line =~ /^disabling ([a-zA-Z0-9]*)/i ) {
    ++$disablings{$1};
}

I created flag variables for the three conditions before the main loop that goes through the file to avoid a regex compilation on every line of the file.

You could also use the Getopt::Long or Getopt::Std modules. These provide easy and flexible handling of the command line arguments.

answered Nov 20, 2012 at 18:30

mpe

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1 Comment

TheBlackCorsair Over a year ago

Thank you @mpe. This is very useful. It is working and I also tried the Getopt::Long module and worked as well.

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