Re: Print question

From: Sherm Pendley (spamtrap_at_dot-app.org)
Date: 01/12/05 

Date: Tue, 11 Jan 2005 21:38:10 -0500

jl_post@hotmail.com wrote:

> Normally, a print() statement in Perl won't print a newline
> unless you tell it to.

Quite correct, but that doesn't answer the question. The OP is asking how to
unbuffer output, so it appears immediately, rather than a line at a time.
To illustrate this, insert a sleep(2) between each of the prints in your
example:

> #!/usr/bin/perl
> use strict;
> use warnings;
> print "H";

sleep(2);

> print "i";

sleep(2);

> print "!";

sleep(2);

> print "\n";
> __END__

You'd think this would print one letter at a time, with a pause in between -
but that's not what happens. What usually happens is a six second pause,
and then "Hi!" printed all at once, because output is buffered. (I say
"usually" because it's an OS feature, not a Perl feature, so it may not
apply to everyone. In particular, I don't know if it's true on Windows.)

The FAQ I mentioned addresses the buffering question. In brief - the FAQ
gives much more detail - you set $| to a true value to disable buffering.

So if you add:
    $| == 1;

To your example, you get what the OP presumably wants from the sleep(2)
calls above - a two-second pause between each letter.

sherm-- 

-- 
Cocoa programming in Perl: http://camelbones.sourceforge.net
Hire me! My resume: http://www.dot-app.org

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