Break out of the sub or loop on keypress

[Michael Alipio]

Hi,

I have a sub that returns a value and inside it runs a loop that displays 
something on the screen, say a list of numbered items. Now what I want to do is 
if the item i'm interested appears on the screen, the user can hit any key and 
the program will exit the sub and return what ever it is supposed to return.

Any idea how to accomplish that?


  

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Re: Break out of the sub or loop on keypress

[Mr. Shawn H. Corey]

On Sat, 2008-08-09 at 14:42 -0700, Michael Alipio wrote:
> Hi,
> 
> I have a sub that returns a value and inside it runs a loop that displays 
> something on the screen, say a list of numbered items. Now what I want to do 
> is if the item i'm interested appears on the screen, the user can hit any key 
> and the program will exit the sub and return what ever it is supposed to 
> return.
> 
> Any idea how to accomplish that?
> 
> 
>   
> 
Yes.  Fork of a child process, use Term::ReadKey to set STDIN to respond
immediately on key press.  When that happens, the child process signals
the parent, which breaks the loop.

See:
perldoc perlipc
perldoc Term::ReadKey


-- 
Just my 0.0002 million dollars worth,
  Shawn

"Where there's duct tape, there's hope."

"Perl is the duct tape of the Internet."
Hassan Schroeder, Sun's first webmaster


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Re: Break out of the sub or loop on keypress

[Rob Dixon]

Michael Alipio wrote:
> 
> I have a sub that returns a value and inside it runs a loop that displays 
> something on the screen, say a list of numbered items. Now what I want to do
> is if the item i'm interested appears on the screen, the user can hit any key
> and the program will exit the sub and return what ever it is supposed to
> return.
> 
> Any idea how to accomplish that?

I'm not clear if the "what ever it is supposed to return" is related to the key
press or not. If not then perhaps the subroutine should be broken into two.

Anyway, it sounds like what you want to do is to break out of a loop when a key
is pressed. The program below prints dots until a key is pressed and then says
how many have been printed. Does that help?

Rob


use strict;
use warnings;

use Term::ReadKey;

my $n = 0;

while () {
  print '.';
  last if ReadKey(-1);
  $n++;
}

print $n;


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