jaco has asked for the wisdom of the Perl Monks concerning the following question:

Fellow Monks
I'm trying to create a script that uses an alarm handler to cause a reoccuring event within a while loop.
To the best of my knowledge the manner at which I'm doing this is acceptable. However, I'm curious
to know if there's a better way. Or perhaps a more proper or stable way. Not that I knowingly find this
unstable, but the line in perlipc
That means that doing nearly anything in your handler could in theory trigger a memory fault and
subsequent core dump.
has always been a concern. Anyway, it's something like ... 
#!/usr/bin/perl


$SIG{ALRM} = sub {alarm(0);print "blah\n";alarm(10);};


open(FILE, "tail -f /var/log/messages|");
$| = 1;
alarm(10);

while(<FILE>){
        print $_;
}

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Re: Reoccuring time based event inside a loop (threads)
by BrowserUk (Patriarch) on Oct 06, 2004 at 17:43 UTC

    It's easy and safe with threads. 

    #! perl -slw
use strict;
use threads qw[ async ];
use threads::shared;

$| = 1;

## Simulate tail
open FILE, q[
    perl -le"$|=1; print and select(undef,undef,undef,.1) for 1 .. 30"
+ |
] or die $!;

my $done : shared  = 0;
my $t = async {
    while( !$done and sleep 1 ) {
        print 'Blah';
    }
};

while( <FILE> ) {
    printf;
}

$done = 1;
$t->join;

__END__
P:\test>397046
1
2
3
4
5
6
7
8
9
10
Blah
11
12
13
14
15
16
17
18
19
Blah
20
21
22
23
24
25
26
27
28
Blah
29
30
Blah

P:\test>

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    Examine what is said, not who speaks.
    "Efficiency is intelligent laziness." -David Dunham
    "Think for yourself!" - Abigail
    "Memory, processor, disk in that order on the hardware side. Algorithm, algorithm, algorithm on the code side." - tachyon
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[d/l]
Re: Reoccuring time based event inside a loop
by Joost (Canon) on Oct 06, 2004 at 16:19 UTC
[reply]

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