SIGBLOCK Section: Linux Programmer's Manual (2) Updated: 31 August 2025 Index   NAME sigblock, siggetmask, sigsetmask, sigmask - manipulate the signal mask   SYNOPSIS #include <signal.h> int sigblock(int mask); int siggetmask(void); int sigsetmask(int mask); int sigmask(int signum);   DESCRIPTION This interface is made obsolete by The sigblock system call adds the signals specified in mask to the set of signals currently being blocked from delivery. The sigsetmask system call replaces the set of blocked signals totally with a new set specified in mask. Signals are blocked if the corresponding bit in mask is a 1. The current set of blocked signals can be obtained using siggetmask. The sigmask macro is provided to construct the mask for a given signum.   RETURN VALUES siggetmask returns the current set of masked signals. sigsetmask and sigblock return the previous set of masked signals.   NOTES Prototypes for these functions are only available if __USE_BSD is defined before <signal.h> is included. It is not possible to block SIGKILL or SIGSTOP - this restriction is silently imposed by the system.   CONFORMING TO 4.4BSD. These function calls appeared in BSD 4.3 and are deprecated. Use the POSIX signal facilities for new programs.   SEE ALSO   Index NAME SYNOPSIS DESCRIPTION RETURN VALUES NOTES CONFORMING TO SEE ALSO This document was created by using the manual pages. Time: 11:56:07 GMT, March 24, 2025