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SIGINTERRUPT(3)       DragonFly Library Functions Manual       SIGINTERRUPT(3)


NAME

     siginterrupt -- allow signals to interrupt system calls


LIBRARY

     Standard C Library (libc, -lc)


SYNOPSIS

     #include <signal.h>

     int
     siginterrupt(int sig, int flag);


DESCRIPTION

     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 has been the default behavior since 4.2BSD, and is
     the default behaviour for signal(3) on DragonFly.

     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 transfer-
     ring 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.


NOTES

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


RETURN VALUES

     The siginterrupt() function returns the value 0 if successful; otherwise
     the value -1 is returned and the global variable errno is set to indicate
     the error.


ERRORS

     The siginterrupt() call fails if:

     [EINVAL]           sig is not a valid signal number.


SEE ALSO

     sigaction(2), sigprocmask(2), sigsuspend(2), signal(3)


HISTORY

     The siginterrupt() function appeared in 4.3BSD.

DragonFly 3.5                    June 4, 1993                    DragonFly 3.5

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