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A "signal" is a way for your program to process "asynchronous" events. Meaning that you register a subroutine to be called when that event occurs. When you do this, you don't have to explictly keep checking that a particular event occured, the OS will call the sub when that event occurs.

kill ALRM, $$ doesn't make sense to me!

The below code shows a simple example of a handler for SIGALRM.

#!/usr/bin/perl -w use strict; #$|=1; #see note below... $SIG{'ALRM'} = 'timeout'; alarm(1); while (1){sleep(1);} sub timeout { print "stdout: Alarming!\n"; print STDERR "stderr: Alarming!\n"; exit(0); }; __END__ prints: Note: stderr msg comes first because "autoflush" for stdout wasn't turned on (stdout normally doesn't get "flushed" until program end). $|=1; turns autoflush on. stderr: Alarming! stdout: Alarming!
Kill $some_number makes no sense if $some_number is not a PID. kill ALRM doesn't have a PID. ALRM on my system is "numeric 14", but that is just shorthand for what the string ALRM means.

In reply to Re: Signals in Strawberry Perl: Name or number? by Marshall
in thread Signals in Strawberry Perl: Name or number? by bv

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