Node:Signaling Yourself, Next:Signaling Another Process, Up:Generating Signals
A process can send itself a signal with the raise
function. This
function is declared in signal.h
.
int raise (int signum) | Function |
The raise function sends the signal signum to the calling
process. It returns zero if successful and a nonzero value if it fails.
About the only reason for failure would be if the value of signum
is invalid.
|
int gsignal (int signum) | Function |
The gsignal function does the same thing as raise ; it is
provided only for compatibility with SVID.
|
One convenient use for raise
is to reproduce the default behavior
of a signal that you have trapped. For instance, suppose a user of your
program types the SUSP character (usually C-z; see Special Characters) to send it an interactive stop signal
(SIGTSTP
), and you want to clean up some internal data buffers
before stopping. You might set this up like this:
#include <signal.h> /* When a stop signal arrives, set the action back to the default and then resend the signal after doing cleanup actions. */ void tstp_handler (int sig) { signal (SIGTSTP, SIG_DFL); /* Do cleanup actions here. */ ... raise (SIGTSTP); } /* When the process is continued again, restore the signal handler. */ void cont_handler (int sig) { signal (SIGCONT, cont_handler); signal (SIGTSTP, tstp_handler); } /* Enable both handlers during program initialization. */ int main (void) { signal (SIGCONT, cont_handler); signal (SIGTSTP, tstp_handler); ... }
Portability note: raise
was invented by the ISO C
committee. Older systems may not support it, so using kill
may
be more portable. See Signaling Another Process.