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 has been the default behavior since
BSD 4.2 ,
and is the default behaviour for
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
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
Note that the new
signal handling semantics are not
altered in any other way.
Most notably, signal handlers always remain installed until
explicitly changed by a subsequent
call, and the signal mask operates as documented in
Programs may switch between restartable and interruptible
system call operation as often as desired in the execution of a program.
call during the execution of a signal handler will cause
the new action to take place on the next signal to be caught.