Hi,

I would like to achieve the following:

Run a command and capture its output. While waiting for output, run a subroutine every 10 seconds. So, I do not want to escape from the while loop, like in most other examples.

In this example, the timer is set off, but it ends the program. I tried positioning the eval block on various places (e.g. outside the while loop), but to no avail. Perhaps it cannot be done and I need to dive into working with threads.

The sleep 120 in this code is only to simulate no response from command.

#!/usr/bin/perl
use strict;
use warnings;
use Time::Local;
use Time::HiRes qw[ time ];
use POSIX ":sys_wait_h";

my $ReturnValue = 0;

sub MainSub()
{
my $Sub = "MainSub";
my $SubReturnValue = 0;

my $CommandLine;
my $Command = qq(echo 'Hallo, sleeping for 120 seconds ...'; sleep 120
+ 2>&1);
open (COMMAND, '-|', "$Command");
while (<COMMAND>) {
    eval {
        local $SIG{ALRM} = sub { die("TimerTriggerStatus\n"); };
        alarm(10);
        printf "%s : %s\n", scalar localtime(), "$Sub - timer set to 1
+0 seconds";
        
        chomp;
        $CommandLine = $_;
        printf "%s : %s\n", scalar localtime(), "$Sub - CommandLine re
+ceived:\n$CommandLine";
    };

    if ( $@ eq "TimerTriggerStatus\n" ) {
        printf "%s : %s\n", scalar localtime(), "$Sub - timer triggere
+d";
        &TimerHandler;
    };
}
close (COMMAND);

return ($SubReturnValue);
} # end of sub MainSub


sub TimerHandler() {
my $Sub = "TimerHandler";
my $SubReturnValue = 0;

printf "%s : %s\n", scalar localtime(), "$Sub - timer expired";

alarm(10);
printf "%s : %s\n", scalar localtime(), "$Sub - timer set to 10 second
+s";

return ($SubReturnValue);

} # end of sub TimerHandler


sub TimerSub() {
my $Sub = "TimerSub";
my $SubReturnValue = 0;

printf "%s : %s\n", scalar localtime(), "$Sub - run after timer interr
+upt";

alarm(10);
printf "%s : %s\n", scalar localtime(), "$Sub - timer set to 10 second
+s";

return ($SubReturnValue);

} # end of sub TimerSub

#### MAIN ####
printf "%s : %s\n", scalar localtime(), "BEGIN - MAIN";
($ReturnValue) = &MainSub;
printf "%s : %s\n", scalar localtime(), "END - MAIN";

[download]

Output when run:

# time ./TestSigalrm.pl
Wed Jul 24 08:38:20 2019 : BEGIN - MAIN
Wed Jul 24 08:38:20 2019 : MainSub - timer set to 10 seconds
Wed Jul 24 08:38:20 2019 : MainSub - CommandLine received:
Hallo, sleeping for 120 seconds ...
Alarm clock

real    0m10.018s
user    0m0.014s
sys     0m0.002s

[download]

In reply to Using SIG{ALRM} within while loop. by evroom

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