[[!meta title="A Lesser-Known Feature of kill(1)"]]
[[!meta author="rohieb"]]
[[!meta license="CC-BY-SA 3.0"]]

## Problem ##
I was debugging a program, which suddenly died with

    QFATAL : TestEdge::testSaveRemove() Received signal 11

For better understanding of the problem, it would be nice to know what
the meaning of “signal 11” is.


## Solution ##
I was not so fluent in signal numbers (maybe I should take [a
course][memrise]). Of course, I _could_ dig in the [`signal(7)` man
page][mansignal], or in the respective C header (`signal.h`). However,
while digging in the manpages, I noticed that `kill(1)` does not only
kill processes, but also does exactly what I want.[^1] Citing from the
[man page][mankill]:

    -l, --list [signal]
      List  signal  names.   This  option has optional argument, which
      will convert signal number to signal name, or other way round.

[^1]: At least the version in Debian, which is from
    [procps](https://gitorious.org/procps)

So I could just say:

    $ kill -l 11
    SEGV

Ah, segmentation fault. Nice to know :-)

In addition, the man page also mentions a useful parameter `-L`, which
prints a nice table of signal numbers and mnemonics:

    $ /bin/kill -L
     1 HUP      2 INT      3 QUIT     4 ILL      5 TRAP     6 ABRT  7 BUS
     8 FPE      9 KILL    10 USR1    11 SEGV    12 USR2    13 PIPE 14 ALRM
    15 TERM    16 STKFLT  17 CHLD    18 CONT    19 STOP    20 TSTP 21 TTIN
    22 TTOU    23 URG     24 XCPU    25 XFSZ    26 VTALRM  27 PROF 28 WINCH
    29 POLL    30 PWR     31 SYS

(Also, the man page also warns about `kill` probably being a shell
built-in. At least the Bash and zsh built-ins also know `-l`, but not
`-L`, so you have to call `/bin/kill` explicitly.)

[memrise]: http://www.memrise.com/course/158486/unix-signals/
[mansignal]: http://manpages.debian.net/cgi-bin/man.cgi?query=signal&apropos=0&sektion=7&manpath=Debian+7.0+wheezy&format=html&locale=en
[mankill]: http://manpages.debian.net/cgi-bin/man.cgi?query=kill&apropos=0&sektion=0&manpath=Debian+7.0+wheezy&format=html&locale=en

[[!tag UNIX Linux Debian UNIX_signal_numbers signal.h SIGSEGV kill]]