The short question is this: should spawning a thread change how signal handlers behave? See below for a working code snippet.

So, I was banging my head against the keyboard trying to remember how to read in a series of lines from STDIN with Win32 ActivePerl. After much googling, I realize that I've only ever gotten characters with Term::ReadKey, and that isn't even close to what I wanted. Apparently, nothing is.

All I wanted to do was this, and be able to type ctrl-D to signify that I was done: 

my @lines = <STDIN>;

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(Somebody let me know if I missed the obvious boat here; I couldn't find the way to do this.)

So, I decided to go with ctrl-C: 

{
   local($SIG{INT}) = 'IGNORE';
   @lines = <STDIN>;
}

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Hmmm... that doesn't work either. It kills my script.

I soon came to realize that I'm using that nifty new Perl v5.8.8 with "safe" signals, and I suspect that this was getting in the way. Sadly, Perl::Unsafe::Signals isn't available via ppm for ActivePerl, so I didn't get to find out either way.

What I did discover, quite by accident was that spawning a thread changes the behavior of the signal handler: 

#!perl -w
use strict;
use threads;

my @lines;
print "Enter CTRL-C to end input\n";
$SIG{INT} = 'IGNORE'; # making this local() causes ctrl-C to kill the 
+script
@lines = <STDIN>;
threads->create( sub{} )->join();
$SIG{INT} = 'DEFAULT';  # putting this after thread creation makes eve
+rything happy
chomp @lines; # kill newlines from STDIN entries

print "Enter CTRL-C to exit\n";
local($") = ', ';
while ( 1 )
{
   print "You entered: @lines\n";
   sleep(1);
}

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So, I'm left wondering if that was supposed to work that way?

In reply to Is the signal handler supposed to work like this? by dpmott

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