of_system_int and to_system_int return and take respectively a signal number corresponding to those in the system's /usr/include/bits/signum.h (or equivalent). It is not guaranteed that these numbers are portable across any given pair of systems -- although some are defined as standard by POSIX.

send signal pid_spec sends signal to the processes specified by pid_spec.

send_i is like send, except that it silently returns if the specified processes don't exist.

send_exn is like send, except that it raises if the specified processes don't exist.

All of send, send_i, and send_exn raise if you don't have permission to send the signal to the specified processes or if signal is unknown.

can_send_to pid returns true if pid is running and the current process has permission to send it signals.

sigprocmask cmd sigs changes the set of blocked signals.

• If cmd is `Set, blocked signals are set to those in the list sigs.
• If cmd is `Block, the signals in sigs are added to the set of blocked signals.
• If cmd is `Unblock, the signals in sigs are removed from the set of blocked signals.

sigprocmask returns the set of previously blocked signals.

sigpending () returns the set of blocked signals that are currently pending.

sigsuspend sigs atomically sets the blocked signals to sigs and waits for * a non-ignored, non-blocked signal to be delivered. On return, the blocked * signals are reset to their initial value.