How can I get a human-readable description from a signal number?

Question

Does the POSIX standard or another C standard provide a way to recover a meaningful message from a signal number, in the same way that strerror() makes it possible to recover a message from errno? The Gnu C library has strsignal(), but if possible, I would like something portable to BSD and other Unix variants.

Answer 1

The externally defined array sys_siglist contains the signal descriptions for each signal number, and is standard issue on BSD.

#include <signal.h>

extern const char *const sys_siglist[];

Answer 2

Yes, interestingly, there is a standard way to get a string message from a signal in POSIX. It is, quite coincidentally, strsignal(). From POSIX.1-2008:

The strsignal() function shall map the signal number in signum to an implementation-defined string and shall return a pointer to it. It shall use the same set of messages as the psignal() function.

An environment that does not provide you this function is not POSIX-compliant. Although relatively new (Issue 7 came out in 2008), I have a man page for strsignal() on Mac OS X, so that's a good sign.