Beefy Boxes and Bandwidth Generously Provided by pair Networks
Perl Monk, Perl Meditation

Comment on

( #3333=superdoc: print w/replies, xml ) Need Help??

Some suggestions below on how to improve the early part of your script.

1) Replace:

if ($#ARGV != 0) { print "One, and only one (not $#ARGV), command line parameter is +expected\n"; exit; }
@ARGV == 1 or die "usage: $0 inputfile\n";
When a script encounters an error it should exit with a non-zero value (a bald exit returns a zero exit value), a usage statement is conventional, and or die is idiomatic.

BTW, you should rarely need to use the cumbersome $#array notation. Using it here is unnecessary and the code is clearer using @ARGV instead. Another example, from Perl Best Practices, chapter 5, "Use negative indices when counting from the end of an array" is to prefer $frames[-2] to $frames[$#frames-1] because it is easier on the eye and avoids the undesirable repetition of the variable name (DRY).

2) Replace:

my $inputFile=$ARGV[0];
my $inputFile = shift;
Using shift makes maintenance easier if you later add or remove command line arguments because you don't need to manually shuffle the ARGV indices (which are "magic numbers").

3) Replace:

if ( not -e $inputFile) { die "$inputFile doesn't exist!!!\nExiting.\n"; }
-f $inputFile or die "input file '$inputFile' does not exist.\n";
Using -f is more precise than -e because the first argument must be a file (not a directory, say). Using or die is idiomatic and more concise.

4) Replace:

open my $file, $inputFile or die "Could not open $inputFile: $!";
open my $file, '<', $inputFile or die "Could not open $inputFile: $!";
As for why the three-argument form of open is preferred, the old two-argument form of open is subject to various security exploits as described at Opening files securely in Perl.

In reply to Re: My first perl script is working, what did I do wrong? by eyepopslikeamosquito
in thread My first perl script is working, what did I do wrong? by killersquirel11

Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":

  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.
  • Log In?

    What's my password?
    Create A New User
    [marto]: glory days ;)
    [hippo]: Too true :)

    How do I use this? | Other CB clients
    Other Users?
    Others lurking in the Monastery: (8)
    As of 2018-06-22 09:58 GMT
    Find Nodes?
      Voting Booth?
      Should cpanminus be part of the standard Perl release?

      Results (124 votes). Check out past polls.