The
siginterrupt() function is used to change the system call restart behavior when a system call is interrupted by the specified signal. If the flag is false (0), then system calls will be restarted if they are interrupted by the specified signal and no data has been transferred yet. System call restart is the default behavior on
4.2BSD.
If the flag is true (1), then restarting of system calls is disabled. If a system call is interrupted by the specified signal and no data has been transferred, the system call will return -1 with the global variable
errno set to
EINTR. Interrupted system calls that have started transferring data will return the amount of data actually transferred. System call interrupt is the signal behavior found on
4.1BSD and AT&T System V UNIX systems.
Note that the new
4.2BSD signal handling semantics are not altered in any other way. Most notably, signal handlers always remain installed until explicitly changed by a subsequent
sigaction(2) call, and the signal mask operates as documented in
sigaction(2). Programs may switch between restartable and interruptible system call operation as often as desired in the execution of a program.
Issuing a
siginterrupt(
3) call during the execution of a signal handler will cause the new action to take place on the next signal to be caught.