4.1cBSD/usr/man/man2/getdopt.2

.TH GETDOPT 2
.UC 4.2
.SH NAME
getdopt, setdopt \- get/set options associated with a descriptor 
.SH SYNOPSIS
.nf
.ft B 
#include <descrip.h>
.PP
.ft B
getdopt(d, whichway, dopt)
int d, whichway;
struct dopt *dopt;
.PP
.ft B
setdopt(d, whichway, dopt)
int d, whichway;
struct dopt *dopt;
.fi
.SH DESCRIPTION
\fBN.B. This call is proposed for 4.2bsd, but not implemented in 4.1c.\fP
.PP
I/O operations on descriptors are normally blocking in case 
a request can not be immediately completed.  This mode of
operation may be altered to be 
.I "non-blocking"
or
.I "asynchronous"
through the 
.I setdopt
call.  The
.I getdopt
call allows a process to find out what mode a descriptor
is presently using.
.PP
The descriptor is indicated as
.IR d .
The
.I whichway
parameter is formed by 
.BR or 'ing 
together the following:
.PP
.nf
.RS
.DT
DOPT_INPUT		0x1	apply to input
DOPT_OUTPUT	0x2	apply to all output
DOPT_EXCEPT	0x4	apply to any exceptional conditions
.RE
.fi
.PP
.I Dopt
is a pointer to a structure of the form
.PP
.nf
.RS
.DT
struct dopt {
	int	do_flags;
	int	do_pid;
};
.sp 1
#define	DOFLAG_DONTBLOCK	0x1
#define	DOFLAG_SIGNALPROC	0x2
#define	DOFLAG_SIGNALPGRP	0x4
.RE
.fi
.PP
Operations on a non-blocking descriptor will either complete
immediately, note an error EWOULDBLOCK, partially complete an
input or output operation, returning a partial count or return
an error EINPROGRESS noting the requested operation is in progress.
.PP
A descriptor which has signalling enabled will cause the specified
process and/or process group to be signalled, with a SIGIO when
input, output, or an in-progress operation completes, or with a SIGURG
signal when an exceptional condition arises.
.SH "RETURN VALUE
If the call succeeds, then the call returns a 0 value.
If an error occurs, a value \-1 is returned and an error
indication is stored in the global variable \fIerrno\fP\|.
.SH ERRORS
The possible errors for \fIgetdopt\fP are:
.TP 15
[EBADF]
\fID\fP is not a valid descriptor.
.TP 15
[EFAULT]
The \fIdopt\fP argument is at an illegal address.
.TP 15
[EACCESS]
The process or process group specified in \fIsetdopt\fP
is not allowed to be signalled by the current process.
.SH "SEE ALSO"
select(2), signal(2)