Assuming other applications visiting this logfile are playing nice too, you could use flock with the LOCK_NB bitflag set (that is Lock Non-Blocking). This will cause flock to return immediately instead of waiting for a lock. When it returns, its status will tell you whether it was granted a lock or not. If not, you know something else has the file locked. Flocking is voluntary, so scripts/programs that don't lock the file or check to see if it's locked won't play nice with applications that do.

As far as reading lines as they're being written, that's precarious. Due to buffering, you're unlikely to get line by line info, but rather chunks every so often.

By the way, another option would be to periodically check last modification time, or file size. A change there will indicate the file has been written to.


Dave

In reply to Re: Is a file currently being modified? by davido
in thread Is a file currently being modified? by njcodewarrior

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.