We mentioned above that the shell prints a message describing the signal
that terminated a child process. The clean way to print a message
describing a signal is to use the functions
psignal. These functions use a signal number to specify which
kind of signal to describe. The signal number may come from the
termination status of a child process (see Process Completion) or it
may come from a signal handler in the same process.
This function returns a pointer to a statically-allocated string containing a message describing the signal signum. You should not modify the contents of this string; and, since it can be rewritten on subsequent calls, you should save a copy of it if you need to reference it later.
This function prints a message describing the signal signum to the standard error output stream
stderr; see Standard Streams.
If you call
psignalwith a message that is either a null pointer or an empty string,
psignaljust prints the message corresponding to signum, adding a trailing newline.
If you supply a non-null message argument, then
psignalprefixes its output with this string. It adds a colon and a space character to separate the message from the string corresponding to signum.
There is also an array
sys_siglist which contains the messages
for the various signal codes. This array exists on BSD systems, unlike