— Macro: int sigmask (int signum)

This macro returns a signal mask that has the bit for signal signum set. You can bitwise-OR the results of several calls to sigmask together to specify more than one signal. For example,

          (sigmask (SIGTSTP) | sigmask (SIGSTOP)
           | sigmask (SIGTTIN) | sigmask (SIGTTOU))

specifies a mask that includes all the job-control stop signals.

— Function: int sigblock (int mask)

This function is equivalent to sigprocmask (see Process Signal Mask) with a how argument of SIG_BLOCK: it adds the signals specified by mask to the calling process's set of blocked signals. The return value is the previous set of blocked signals.

— Function: int sigsetmask (int mask)

This function equivalent to sigprocmask (see Process Signal Mask) with a how argument of SIG_SETMASK: it sets the calling process's signal mask to mask. The return value is the previous set of blocked signals.

— Function: int sigpause (int mask)

This function is the equivalent of sigsuspend (see Waiting for a Signal): it sets the calling process's signal mask to mask, and waits for a signal to arrive. On return the previous set of blocked signals is restored.