The following values for the sa_flags member of the
sigaction structure are defined for Linux.
SA_NOCLDSTOP: Don't send SIGCHLD when a child process
SA_RESTART: Force restart of certain system calls when
interrupted by a signal handler.
SA_NOMASK: Disable signal mask (which blocks signals during
execution of a signal handler).
SA_ONESHOT: Clear signal handler after execution. Note that
SVR4 uses SA_RESETHAND to mean the same thing.
SA_INTERRUPT: Defined under Linux, but unused. Under SunOS,
system calls were automatically restarted, and this flag disabled that
SA_STACK: Currently a no-op, to be used for signal stacks.
Note that POSIX.1 defines only SA_NOCLDSTOP, and there are
several other options defined by SVR4 not available under Linux.
When porting applications which use sigaction, you may have to
modify the values of sa_flags to get the appropriate behavior.