freebsd-dev/lib/libc/sys/syscall.2
Warner Losh fbbd9655e5 Renumber copyright clause 4
Renumber cluase 4 to 3, per what everybody else did when BSD granted
them permission to remove clause 3. My insistance on keeping the same
numbering for legal reasons is too pedantic, so give up on that point.

Submitted by:	Jan Schaumann <jschauma@stevens.edu>
Pull Request:	https://github.com/freebsd/freebsd/pull/96
2017-02-28 23:42:47 +00:00

78 lines
2.7 KiB
Groff

.\" Copyright (c) 1980, 1991, 1993
.\" The Regents of the University of California. All rights reserved.
.\"
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.\" modification, are permitted provided that the following conditions
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.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of the University nor the names of its contributors
.\" may be used to endorse or promote products derived from this software
.\" without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\"
.\" @(#)syscall.2 8.1 (Berkeley) 6/16/93
.\" $FreeBSD$
.\"
.Dd June 16, 1993
.Dt SYSCALL 2
.Os
.Sh NAME
.Nm syscall ,
.Nm __syscall
.Nd indirect system call
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/syscall.h
.In unistd.h
.Ft int
.Fn syscall "int number" ...
.Ft off_t
.Fn __syscall "quad_t number" ...
.Sh DESCRIPTION
The
.Fn syscall
function
performs the system call whose assembly language
interface has the specified
.Fa number
with the specified arguments.
Symbolic constants for system calls can be found in the header file
.In sys/syscall.h .
The
.Fn __syscall
form should be used when one or more of the arguments is a
64-bit argument to ensure that argument alignment is correct.
This system call is useful for testing new system calls that
do not have entries in the C library.
.Sh RETURN VALUES
The return values are defined by the system call being invoked.
In general, a 0 return value indicates success.
A -1 return value indicates an error,
and an error code is stored in
.Va errno .
.Sh HISTORY
The
.Fn syscall
function appeared in
.Bx 4.0 .
.Sh BUGS
There is no way to simulate system calls that have multiple return values
such as
.Xr pipe 2 .