Sunday, April 27, 2008

Perl Script To Translate Signal Names And Numbers

Hey There,

For this "Lazy Sunday" post I threw together a quick little Perl script to help out further with what we went over more thoroughly in our previous post on signal definitions in Linux and Unix.

This script takes at least one argument (or it throws a fit and refuses to cooperate with you ;) of either a signal name or signal number, which it will then translate to the other (does the way I wrote that make sense? ;)

So, if you want to know what signals 4 and 5 do, you could run:

host # ./ 4 5
Signal Number 4 = ILL
Signal Number 5 = TRAP

And see the (somewhat more verbose) translations from the system includes. Conversely, you could want to know what numbers the TERM and KILL signals are, which you could get by running:

host # ./ TERM KILL
Signal Name TERM = 15
Signal Name KILL = 9

Or you can mix and match. Do whatever, you want. If you throw the script an argument it doesn't understand it will react accordingly ;)

host # ./ hup 8 ... 9
Signal Name HUP = 1
Signal Number 8 = FPE
...: What is that supposed to mean?
Signal Number 9 = KILL

One interesting thing in the script is the use of an absolute subroutine call. Even though I put the "use Sys::SigAction;" line in the script, Perl was interpreting the function calls (like sig_number()) as belonging to the Main:: module. Pretty much every function, or command, in Perl does. "print," for example, is actually Main::print, so I had to use "absolute" naming. Writing "Sys::SigAction::sig_number()" (in this instance) is one way to make sure that Perl knows exactly where to look for that subroutine to run :)


Creative Commons License

This work is licensed under a
Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License


# 2008 - Mike Golvach -
# Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License

if ( $#ARGV < 0 ) {
print "Usage: $0 signalNumber1 [signalNumbern...]\n";

use Sys::SigAction;

@signos = @ARGV;

foreach $sig (@signos) {
if ( $sig =~ /[A-Za-z]+/ ) {
$sig = uc($sig);
$signum=Sys::SigAction::sig_number( $sig );
print "Signal Name $sig = $signum\n";
} elsif ($sig =~ /[0-9]+/) {
$signame=Sys::SigAction::sig_name( $sig );
print "Signal Number $sig = $signame\n";
} else {
print "$sig: What is that supposed to mean?\n";

, Mike