The
psignal() function locates the descriptive message string for the given signal number
sig and writes it to the standard error.
If the argument
s is non-
NULL it is written to the standard error file descriptor prior to the message string, immediately followed by a colon and a space. If the signal number is not recognized (
sigaction(2)), the string “Unknown signal” is produced.
The
psiginfo() function produces the same output as the
psignal() function, only it uses the signal number information from the
si argument.
The message strings can be accessed directly using the external array
sys_siglist, indexed by recognized signal numbers. The external array
sys_signame is used similarly and contains short, upper-case abbreviations for signals which are useful for recognizing signal names in user input. The defined variable
NSIG contains a count of the strings in
sys_siglist and
sys_signame.