On Feb 4, Nilay Puri, Noida said:
>> Can any one help me understand the usage of special variable $| ?
>>
>> I know the description of this var. If set to nonzero, forces a flush
>> after every write or print.
Most filehandles buffer their output until a newline is reached. For
example, try this code:
for (1 .. 5) {
print STDOUT;
sleep 1;
}
At the end of 5 seconds, you'll get "12345". Compare that with this:
for (1 .. 5) {
print STDERR;
sleep 1;
}
Here, you get 1, then a pause, 2, then a pause, and so on. STDOUT is
buffered, whereas STDERR is not. Now, if you want to UNbuffer STDOUT, you
set $| to 1.
$| = 1;
for (1 .. 5) {
print STDOUT;
sleep 1;
}
Now you get 1, pause, 2, pause, 3, pause, 4, pause, 5, pause.
$| has its own value for each filehandle. In order to make filehandle FOO
unbuffered, you need to select() FOO and then set $| to 1.
my $old_fh = select FOO;
$| = 1; # now FOO is unbuffered
select $old_fh; # go back to whatever filehandle was previous selected
--
Jeff "japhy" Pinyan [EMAIL PROTECTED] http://www.pobox.com/~japhy/
RPI Acacia brother #734 http://www.perlmonks.org/ http://www.cpan.org/
<stu> what does y/// stand for? <tenderpuss> why, yansliterate of course.
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