It's better to not open files until you need them. Personally, I think it's better to close them when you're done, but depending on the script it can be ok to leave them for the garbage collector. In my opinion that's just sloppy, but there are reasons to do it.

You can learn a lot about this from the open page alone.

What they do depends on the platform you're on. In *nix there are system calls that get made to the kernel requesting filehandles and readwrites and things. Perl buffers all this stuff and gives you a really nice interface (several actually) to use. In windows, I can only assume it's similar, but don't really know for sure. The details of system level IO represent an enormous discussion that you can safely ignore (for the most part) in perl.

-Paul

In reply to Re: What happens when I use a filehandle by jettero
in thread What happens when I use a filehandle by Anonymous Monk

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.