Beefy Boxes and Bandwidth Generously Provided by pair Networks
"be consistent"

Comment on

( #3333=superdoc: print w/ replies, xml ) Need Help??

I have a program which loops indefinitely, and every 30 seconds checks for a condition and prints to a log file if the condition exists. But this distilled version of the code does not print out to the logfile:

use strict; use warnings; $|++; # make buffer 1 (error happens with or without this) open LOG,">foo.log" or die "can't open foo.log: $!"; while (1) { print LOG (localtime).": something\n"; sleep(30); # if I comment this, print works }

As noted, if I comment out the sleep(30) line, the code writes out to the logfile while the program is running.

I also noted that if if I modify the code so it closes the logfile, it does write to the logfile:

use strict; use warnings; $|++; # make buffer 1 (error happens with or without this) open LOG,">foo.log" or die "can't open foo.log: $!"; for (my $t=0;$t<3;$t++) { print LOG (localtime).": something\n"; sleep(30); } close LOG or die "can't close log: $!";

But it seems to me that the first example ought to work. Any ideas of why this happens? I'm using Perl 5.6, and this happens from both my Linux machine and from ActiveState Perl 5.60. BTW, I can think of other ways to do this, I'm mostly curious as to what causes it not to work. Thanks.


In reply to open, sleep, & print together cause an error by zeno

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, 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, 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.
  • Log In?

    What's my password?
    Create A New User
    and the web crawler heard nothing...

    How do I use this? | Other CB clients
    Other Users?
    Others making s'mores by the fire in the courtyard of the Monastery: (5)
    As of 2015-11-29 09:42 GMT
    Find Nodes?
      Voting Booth?

      What would be the most significant thing to happen if a rope (or wire) tied the Earth and the Moon together?

      Results (750 votes), past polls