Manual Pages  — PSIGNAL

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 psiginfo() function is similar to psignal(), except that the signal number information is taken from the si argument which is a siginfo_t structure.

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, 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.