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.Dd $Mdocdate: May 31 2007 $
.Dt SIGINTERRUPT 3
.Os
.Sh NAME
.Nm siginterrupt
.Nd allow signals to interrupt system calls
.Sh SYNOPSIS
.Fd #include <signal.h>
.Ft int
.Fn siginterrupt "int sig" "int flag"
.Sh DESCRIPTION
The
.Fn siginterrupt
function is used to change the system call restart
behavior when a system call is interrupted by the specified signal.
If
.Fa flag
is false (0), system calls will be restarted if
they are interrupted by the specified signal
.Fa sig
and no data has been transferred yet.
System call restart is the default behavior on
.Ox .
.Pp
If
.Fa flag
is true (1),
the 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
.Va errno
set to
.Er 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
.Bx
systems prior to
.Bx 4.2
as well as most systems based upon
.At V .
.Pp
Programs may switch between restartable and interruptible
system call operation as often as desired in the execution of a program.
Issuing a
.Fn siginterrupt
call during the execution of a signal handler will cause
the new action to take place on the next signal to be caught.
.Sh RETURN VALUES
.Fn siginterrupt
returns 0 on success or \-1 if an invalid signal number has been
specified.
.Sh SEE ALSO
.Xr sigaction 2 ,
.Xr sigprocmask 2 ,
.Xr sigsuspend 2
.Sh HISTORY
The
.Fn siginterrupt
function appeared in
.Bx 4.3 .