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). Of course, I could dig in the signal(7) man page, 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:

-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

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.)