perldoc -f sleep

while( sleep 120 ) { 
  # do what you want
}
[download]

I've never seen it used as the condition of a while loop. I rather like that.

What I've always done it just inset it in the code

while (#Files do not yet exist)
{
sleep(120);
#check for files;
}
[download]

As an alternative to sleeping if you are on Linux (or indeed Irix) with FAM installed - you might consider using SGI::FAM which will allow your program to get events when the contents of a directory changes:

          use SGI::FAM;
         my $fam=new SGI::FAM;
         $fam->monitor('foo');
         while (1) {
           my $event=$fam->next_event; # Blocks
           print "Pathname: ", $event->filename,
             " Event: ", $event->type, "\n";
         }
[download]

/J\

Looks like there is a nice opportunity to do a File::ChangeNotify that presents a unified interface to Win32::ChangeNotify and SGI::FAM (which has got to be one the worst module names i've seen in ages.)



---
demerphq


First they ignore you, then they laugh at you, then they fight you, then you win.
-- Gandhi

#!/usr/bin/perl
use warnings;
use strict;
use Tk;

#read  (perldoc -f stat). 

my $file = shift or die "No file given $!\n";
my $timer;
my $lastmtime = (stat $file)[9];

my $mw= tkinit;
$mw->withdraw;   #make it in background 
$mw->geometry('+20+20'); #set in upper left corner 

my $label = $mw->Label(
       -text => "$file modified at $lastmtime ")->pack(-expand =>1);

&startwatchdog($lastmtime);

$mw->Button(-text => 'Ok',
            -command => sub{
                    $mw->withdraw;
                    $timer->cancel;
                    &startwatchdog( $lastmtime );
                })->pack();
MainLoop;

sub startwatchdog{
my $mtime = shift;

$timer = $mw->repeat(5000, sub { # check every 5 seconds. 
             if ((stat $file)[9] > $lastmtime) {
                # file was modified. 
                # create your dialog box. 
                $lastmtime = (stat $file)[9];
                print "file modified at $lastmtime \n", chr(07);
                $label->configure(-text =>"$file modified at $lastmtim
+e");
                $mw->deiconify;
                $mw->raise;
         }
  });


}
[download]

Alarm is useful if you want to remind yourself to check for the files in two minutes, but do something else in the meanwhile. It's also good for timing out blocking system calls.

Frankly I don't see how it can be useful here, unless you do something like

$SIG{ALRM} = 'IGNORE';
alarm 120;
sleep; # forever, or until interrupted
[download]

Which is, IMHO, a redundant and less reliable way to get the same effect as

sleep 120;
[download]

-nuffin
zz zZ Z Z #!perl