1.\" Copyright (c) 1980, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)syscall.2 8.1 (Berkeley) 6/16/93 33.\" $FreeBSD$ 34.\" 35.Dd June 16, 1993 36.Dt SYSCALL 2 37.Os 38.Sh NAME 39.Nm syscall , 40.Nm __syscall 41.Nd indirect system call 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.In sys/syscall.h 46.In unistd.h 47.Ft int 48.Fn syscall "int number" ... 49.Ft off_t 50.Fn __syscall "quad_t number" ... 51.Sh DESCRIPTION 52The 53.Fn syscall 54function 55performs the system call whose assembly language 56interface has the specified 57.Fa number 58with the specified arguments. 59Symbolic constants for system calls can be found in the header file 60.Ao Pa sys/syscall.h Ac . 61The 62.Fn __syscall 63form should be used when one or more of the arguments is a 6464-bit argument to ensure that argument alignment is correct. 65This system call is useful for testing new system calls that 66do not have entries in the C library. 67.Sh RETURN VALUES 68The return values are defined by the system call being invoked. 69In general, a 0 return value indicates success. 70A -1 return value indicates an error, 71and an error code is stored in 72.Va errno . 73.Sh BUGS 74There is no way to simulate system calls that have multiple return values 75such as 76.Xr pipe 2 . 77.Sh HISTORY 78The 79.Fn syscall 80function appeared in 81.Bx 4.0 . 82