Most notably, signal handlers always remain installed until explicitly changed by a subsequent sigaction or sigvec call, and the signal mask operates as documented in the sigaction subroutine. Programs can switch between restartable and interruptible subroutine operations as often as desired in the running of a program. Issuing a siginterrupt call during the running of a signal handler causes the new action to take place on the next signal caught. Restart does not occur unless it is explicitly specified with the sigaction or sigvec subroutine in the libc.a library. Parameters Signal Indicates the signal .
Flag Indicates true or false.
A value of 0 indicates that the call succeeded. A value of -1 indicates that the supplied signal number is not valid. The sigaction or sigvec subroutine, sigpause subroutine, sigsetmask or sigblock subroutine.