The bsd_signal() function provides a partially compatible interface for programs written to historical system interfaces (see USAGE below).

The function call bsd_signal(sig, func) has an effect as if implemented as:

void (*bsd_signal(int sig, void (*func)(int)))(int) { struct sigaction act, oact; act.sa_handler = func; act.sa_flags = SA_RESTART; sigemptyset(&act.sa_mask); sigaddset(&act.sa_mask, sig); if (sigaction(sig, &act, &oact) == -1) return(SIG_ERR); return(oact.sa_handler); }

The handler function should be declared:

void handler(int sig);

where sig is the signal number. The behavior is undefined if func is a function that takes more than one argument, or an argument of a different type.

Upon successful completion, bsd_signal() returns the previous action for sig. Otherwise, SIG_ERR is returned and errno is set to indicate the error.

Refer to sigaction(2).

This function is a direct replacement for the BSD signal(3UCB) function for simple applications that are installing a single-argument signal handler function. If a BSD signal handler function is being installed that expects more than one argument, the application has to be modified to use sigaction(2). The bsd_signal() function differs from signal (3UCB) in that the SA_RESTART flag is set and the SA_RESETHAND will be clear when bsd_signal() is used. The state of these flags is not specified for signal(3UCB).

sigaction(2), sigaddset(3C), sigemptyset(3C), signal(3UCB)