Recipe 16.13. Listing Available Signals
Author: Tom Christiansen & Nathan Torkington
Date: 1999-07-02T01:44:08Z

#

| Chapter 16 Process Management and Communication |

## 16.13. Listing Available Signals

### Problem

You want to know the signals your operating system provides.

### Solution

If your shell has a built-in kill -l command, use it:

    % kill -l
    HUP INT QUIT ILL TRAP ABRT BUS FPE KILL USR1 SEGV USR2 PIPE
    ALRM TERM CHLD CONT STOP TSTP TTIN TTOU URG XCPU XFSZ VTALRM
    PROF WINCH POLL PWR

Or using just Perl, print the keys in `%SIG` if you have release 5.004 or later:

    % perl -e 'print join(" ", keys %SIG), "\n"'
    XCPU ILL QUIT STOP EMT ABRT BUS USR1 XFSZ TSTP INT IOT USR2 INFO TTOU
    ALRM KILL HUP URG PIPE CONT SEGV VTALRM PROF TRAP IO TERM WINCH CHLD
    FPE TTIN SYS

Before version 5.004, you had to use the Config module:

    % perl -MConfig -e 'print $Config{sig_name}'
    ZERO HUP INT QUIT ILL TRAP ABRT EMT FPE KILL BUS SEGV SYS PIPE ALRM
    TERM URG STOP TSTP CONT CHLD TTIN TTOU IO XCPU XFSZ VTALRM PROF WINCH
    INFO USR1 USR2 IOT

### Discussion

If your version of Perl is before 5.004, you have to use `signame` and `signo` in Config to find the list of available signals, since `keys` `%SIG` wasn't implemented then.

The following code retrieves by name and number the available signals from Perl's standard Config.pm module. Use `@signame` indexed by number to get the signal name, and `%signo` indexed by name to get the signal number.

    use Config;
    defined $Config{sig_name} or die "No sigs?";
    $i = 0;                     # Config prepends fake 0 signal called "ZERO".
    foreach $name (split(' ', $Config{sig_name})) {
        $signo{$name} = $i;
        $signame[$i] = $name;
        $i++;
    }

### See Also

The documentation for the standard Config module, also in Chapter 7 of Programming Perl; the "Signals" sections in Chapter 6 of Programming Perl and in perlipc (1)

16.12. Sharing Variables in Different Processes |  | 16.14. Sending a Signal