console print issue

[Bigus]

This is driving me nuts and I've had it working in different scripts
before.. here's the code:

for($i=0;$i<5;$i++){
sleep 2;
print ">";
}

that should cause an angle bracket to be printed on the commandline every 2
seconds, but instead all 5 are printed at the same time when it's finished
the loop. Can anyone shed any light on why?

Bigus

 

[Eugene Mikheyev]

that should cause an angle bracket to be printed on the commandline every
2

seconds, but instead all 5 are printed at the same time when it's finished
the loop. Can anyone shed any light on why?

Sure, just turn on the autoflash.
$| = 1;

 

[Bigus]

every

Sure, just turn on the autoflash.
$| = 1;

that's odd, because I've never used $| before and in some of my previous
scripts where I've looped through a folder of log files I've included a
progress-bar style thing, like:

where the first row of brackets is the number of log files and on the second
row a bracket is printed after each file has been processed.. and it's
worked fine. I guess something else must have forced a flush of teh print
statements in those cases.

Anyway, thanks

 

[Paul Lalli]

that's odd, because I've never used $| before and in some of my previous
scripts where I've looped through a folder of log files I've included a
progress-bar style thing, like:


where the first row of brackets is the number of log files and on the second
row a bracket is printed after each file has been processed.. and it's
worked fine. I guess something else must have forced a flush of teh print
statements in those cases.

Anyway, thanks

STDOUT defaults to line-buffering (when set to the terminal), files
default to block-buffering. This could account for the differences you
see. Also, printing a newline character flushes the buffer as well.

perldoc -q flush
and
perldoc perlop (search for $!)

for more info.

Paul Lalli

 

[J. Romano]

Sure, just turn on the autoflash.
$| = 1;

If you prefer not to use the autoflush feature, but rather be able
to flush manually, you can always require the "flush.pl" module and
call "flush(*STDOUT)" whenever you need to, like in this example:

#!/usr/bin/perl -w
use strict;
require "flush.pl";

for (1 .. 5)
{
sleep 2;
print ">";
flush(*STDOUT);
}
__END__


-- Jean-Luc

 

[John W. Krahn]

that's odd, because I've never used $| before and in some of my previous
scripts where I've looped through a folder of log files I've included a
progress-bar style thing, like:


where the first row of brackets is the number of log files and on the second
row a bracket is printed after each file has been processed.. and it's
worked fine. I guess something else must have forced a flush of teh print
statements in those cases.

You could have been printing to STDERR which isn't buffered.


John