The psignal and strsignal functions locate the descriptive message string for a signal number.
The strsignal function accepts a signal number argument sig and returns a pointer to the corresponding message string.
The psignal function accepts a signal number argument sig and writes it to the standard error. If the argument s is non- NULL and does not point to the null character, s 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 message strings can be accessed directly through the external array sys_siglist, indexed by recognized signal numbers. The external array sys_signame is used similarly and contains short, lower-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.
sigaction(2), perror(3), strerror(3)