Using print to overwrite a line

[Paul Harwood]

Is there a simple way to print over an existing line?

For example: I would like to have a progress report that reads 10%, 20%
etc. I don't want to print a new line each time. I want to write over
the existing line and have it update as it goes.

--Paul

[Bob Showalter]

Paul Harwood wrote:

> Is there a simple way to print over an existing line?
>
> For example: I would like to have a progress report that
> reads 10%, 20%
> etc. I don't want to print a new line each time. I want to write over
> the existing line and have it update as it goes.
>
> --Paul

Use "\r" to move to the beginning of the current line (depending on the
capabilities of your terminal). Also unbuffer STDOUT. Something like this:

$| = 1;
for (1 .. 5) {
print "\rStep $_";
sleep 1;
}
print "\rFinished.\n";

[Rob Dixon]

Paul Harwood wrote:

>
> Is there a simple way to print over an existing line?
>
> For example: I would like to have a progress report that reads 10%, 20%
> etc. I don't want to print a new line each time. I want to write over
> the existing line and have it update as it goes.

Hi Paul.

I presume you're writing to a file? Can you show us an example of what
you mean? It's probably best if you rewrite the file, but that's not
a problem.

Rob

[Hacksaw]

This is not the most elegant solution, but it did only take me five minutes.
The salient part is the backspace and printing blanks bit. A more elegent
solution would figure out how to destructively clear the line using something
from ncurses.

#!/usr/bin/perl -w

$|=1;

@reports = ("starting", "now we're cooking", "Almost half!", "Over the hump",
"Almost done!", "Finito!");
#print @reports;

foreach $item (@reports)
{
print $item;

sleep 1;
print "\b" x length($item);
print ' ' x length($item);
print "\b" x length($item);

}

--
Music so wishes to be heard that it calls on some to give it voice and some to
give it ears.
[url]http://www.hacksaw.org[/url] -- [url]http://www.privatecircus.com[/url] -- KB1FVD

[Flimm]

This doesn't work if the line being printed is longer than the width of the terminal.