SIGINTERRUPT(3V)

NAME
siginterrupt - allow signals to interrupt system calls

SYNOPSIS

int siginterrupt(sig, flag)
int sig, flag;

DESCRIPTION

siginterrupt() 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, and on SunOS in the 4.2 environment, when the signal (3V) routine is used.

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 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 older version of the UNIX operating systems, such as 4.1BSD and System V UNIX. It is the default behavior on SunOS in the System V environment when the signal() routine is used; therefore, this routine is useful in that environment only if a signal that a sigvec(2) specified should restart system calls is to be changed not to restart them.

Note: 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 sigvec() call, and the signal mask operates as documented in sigvec(), unless the SV_RESETHAND bit has been used to specify that the pre-4.2BSD signal behavior is to be used. Programs may switch between restartable and interruptible system call operation as often as desired in the execution of a program.

Issuing a siginterrupt() call during the execution of a signal handler will cause the new action to take place on the next signal to be caught.

NOTES

This library routine uses an extension of the sigvec(2) system call that is not available in 4.2BSD, hence it should not be used if backward compatibility is needed.

RETURN VALUES

siginterrupt() returns:

0   on success.

-1  if an invalid signal number was supplied.

SEE ALSO
sigblock(2), sigpause(2V), sigsetmask(2), sigvec(2), signal(3V)