SIGINTERRUPT

Section: C Library Functions (3)
Updated: May 15, 1985
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NAME

siginterrupt - allow signals to interrupt system calls

SYNOPSIS

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 4.2 BSD.

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 4.1 BSD and AT&T System V UNIX systems.

Note that the new 4.2 BSD signal handling semantics are not altered in any other way. Most notably, signal handlers always remain installed until explicitly changed by a subsequent sigvec(2) call, and the signal mask operates as documented in sigvec(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.

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 VALUE

A 0 value indicates that the call succeeded. A -1 value indicates that an invalid signal number has been supplied.

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