$|++;
print "  ";
for (0..20) {
    select undef, undef, undef, 0.25;
    print "\b\b";
    printf "%2d", $_;
}
print "\n";
[download]

_________
broquaint

You're not actually going to update the contents of STDOUT, you're going to exploit your terminal in order to move the cursor around.

You could look at Term::* and Curses::*. There, you will find a vast array of terminal manipulation routines.

You could use the backspace character (\b), as someone just mentioned.

Update: or carriage return (\r)

--
¤ Steve Marvell

> perl -e "for(1..10){print qq(\r$_.);select undef,undef,undef,0.5}"
[download]

You could try using backspaces to back up over the previous number and overwrite it. Or use the ANSI cursor escape sequences to move back to the start of the line or directly to the position on the line and overwrite.

The following code is good Perl, but it does work.

#!e:\perl\bin\perl.exe -w
use strict;
use warnings;
use diagnostics;

for( my $n=1; $n<1000; $n++) {
    my $back = length $n;
    print $n, substr "\b\b\b\b", 0, $back;
}

[download]

As well as the other methods suggested in this thread you can also (if you are on a unix box at least) use "tput" to move the cursor around.

system("tput cup 4 10");

will move the cursor to position 4,10 (top left is 0,0 so we are down 4 and across 10). Probably a bit of an overkill where \b might do :)

--
my $chainsaw = 'Perl';

$|++;

for ($i=0; $i<1000; $i++) {
    print "\r$i";
}
print "\n";
[download]

Use "\r" to send the cursor back to the beginning of the line. If you use \b to backspace one character, you'd have to keep up with how long $i has become, and/or add/remove \b's if you change the text of your status line. Send the cursor to the front of the line, reprint the whole thing and be done with it.

Print a \n at the bottom of the loop. Otherwise your terminal prompt (or the next line of output) will get displayed at the end of the last status line and just look plain weird (especially if it starts with a number :) ).

HTH

/\/\averick
OmG! They killed tilly! You *bleep*!!

perl -ne "print qq/\r$. lines processed/;select undef, undef, undef, 0
+.2" your_file_here
[download]

~Particle *accelerates*

You can call a system("clear") before each print statement.