Today I needed a regex in order to validate a MAC address field from a form. The other responses in this thread are excellent, but here's another alternative for this task: 
^(?:[[:xdigit:]]{1,2}[-:]){5}[[:xdigit:]]{1,2}$

[download]
I wanted to allow a user to type in a:b:c:d:e:f instead of 0a:0b:0c:0d:0e:0f, hence the {1,2} quantifiers. Using the POSIX character class :xdigit: tidies things up and makes it obvious what input is required, which helps document the code. I liked petdance's solution (++), but didn't use it because in my application I only wanted to allow ':' as the separator.

Thanks to the helpful CB people who assisted me with this: blakem, demerphq, davorg & Petruchio.

In reply to Re: Regular Expression for MAC Address by virtualsue
in thread Regular Expression for MAC Address by marius

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.