Perl print line example - How to print a specified line from a text file

Have you ever needed a program to print a specific line from a text file? I had this need a long time ago, and I wrote a Perl program to do just that, and I'd like to share it here.

There are certainly more Perl-ish ways to write a program to print a specific line from a text file, but hey, I don't use Perl that much these days, and I can still read this one. :)

Here's the source code for a Perl script I named perl-print-line.pl:

#!/usr/bin/perl

# purpose: print a specific line from a text file
# usage:   perl-print-line.pl line-number input-file

# use perl argv to verify the number of command line arguments
@ARGV == 2 or die "Usage: print-specific-line.pl line-number input-file\n";
$desired_line_number = $ARGV[0];
$filename = $ARGV[1];

# use perl open function to open the file (or die trying)
open(FILE, $filename) or die "Could not read from $filename, program halting.";

# loop through the file with a perl while loop, stopping when you get to the desired record
$count = 1;
while (<FILE>)
{
  if ($count == $desired_line_number)
  {
    # print line, then get out of here
    print $_;
    close FILE;
    exit;
  }
  $count++;
}
close FILE;

print "Sorry, I think the line number you entered is greater than the number of lines in the file.\n";

Example Perl print line program output

Okay, well there really isn't any exciting about the example output from this program, but to be clear, this is how I run this Perl script:

perl perl-print-line.pl 1000 my-long-file

The Perl way

If you really want to approach this problem "the Perl way", you'll probably want to look at the special Perl variable named $., but that's all I'll say about it. :) Sorry, but I'm not real big on memorizing special variables when I'm working with a half-dozen different programming languages.

 

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