Meridius has asked for the wisdom of the Perl Monks concerning the following question:

Can some one tell me how sleep is working. If i am giving sleep inside loop witout "\n" its not working.
This code is not working 
while(1){
     print  "Test";
     sleep(1);
}

[download]

whereas this is working 
while(1){
     print  "Test\n";
     sleep(1);
}

[download]
-Meridius-

Replies are listed 'Best First'.
Re: Sleep Not Sleeping when using without "\n"
by ikegami (Patriarch) on Mar 24, 2005 at 06:11 UTC
    STDOUT is buffered. "\n" forces the buffer to empty, and so does auto-flushing. Turn auto-flushing with $|=1, and the "\n" won't be necessary for the print to work immediately.
[reply]
[d/l]
      Or just be very, very, patient :)
[reply]
        From the Suffering from Buffering article, link in comment below, we get the line: "The blocks on your disk are probably about 8K bytes."

        Using that, and your original, non '\n', case, plus the sleep of 1 second, we get:

           8K = 8 * 1024 = 8192 bytes
   'test' = 4 bytes
   8192/4 = 2048 = # of times output will need to happen before you se
+e anything due to buffering.
   2048 * 1 second sleeps between each output = 2048 seconds
   2048 / 60 seconds per minute = 34.1333 minutes to wait.

        [download]
        -Scott
[reply]
[d/l]
Re: Sleep Not Sleeping when using without "\n"
by BUU (Prior) on Mar 24, 2005 at 06:31 UTC
[reply]

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