__FILE__ is the file name that the __FILE__ token is in, and $0 is a variable containing the name of the program, as given to the shell.

They can most certainly be different - one case that comes to mind is a __FILE__ token in a library called by your program, but there are many others, particularly since you can assign to $0 (with varying effects on different OS), but you can't meaningfully assign to __FILE__.

Example code:

File 1 - firstfile

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

print $0 . "\n";
print __FILE__ . "\n";

do 'filetwo';

[download]

File 2 - filetwo

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

print $0 . "\n";
print __FILE__ . "\n";

[download]

It's simplistic, but should show the basic concept.

for(split(" ","tsuJ rehtonA lreP rekcaH")){print reverse . " "}print "\b.\n";

In reply to Re: Difference between $0 and __FILE__ by pobocks
in thread Difference between $0 and __FILE__ by solegaonkar

Title:
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, details, 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, summary, 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.