ikegami is right that you can use pack and unpack create / read from structs. however, using pack() to write structs does not work portably, especially when you've got a struct made up of different-sized elements - AFAIK C compilers are allowed to switch elements in struct around, and anyway insert unused bytes to align elements depending on their type. IOW: 

struct {
  byte a;
  long b;
}

[download]

may take up 6 bytes on a system with 4-byte integers and a 2-byte alignment requirement for integers. OTOH on a system with 4-byte aligned 4-byte integers, it might take up 8 bytes.

Ofcourse, there are modules to deal with all of this, a CPAN search gave me this (probably incomplete) list:

note - I've not tested any of these and if none of them work, I know Inline::C does, but it's probably overkill for this application. Also, if you only need it to work on a specific system, you can hardcode the pack() template anyway (you might have to experiment to get the right one).

"What should it profit a man, if he should win a flame war, yet lose his cool?"

In reply to Re: Using ioctl() by Joost
in thread Using ioctl() by chriswalsh

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.