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. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)syscall.2 8.1 (Berkeley) 6/16/93 29.\" $FreeBSD$ 30.\" 31.Dd June 16, 1993 32.Dt SYSCALL 2 33.Os 34.Sh NAME 35.Nm syscall , 36.Nm __syscall 37.Nd indirect system call 38.Sh LIBRARY 39.Lb libc 40.Sh SYNOPSIS 41.In sys/syscall.h 42.In unistd.h 43.Ft int 44.Fn syscall "int number" ... 45.Ft off_t 46.Fn __syscall "quad_t number" ... 47.Sh DESCRIPTION 48The 49.Fn syscall 50function 51performs the system call whose assembly language 52interface has the specified 53.Fa number 54with the specified arguments. 55Symbolic constants for system calls can be found in the header file 56.In sys/syscall.h . 57The 58.Fn __syscall 59form should be used when one or more of the arguments is a 6064-bit argument to ensure that argument alignment is correct. 61This system call is useful for testing new system calls that 62do not have entries in the C library. 63.Sh RETURN VALUES 64The return values are defined by the system call being invoked. 65In general, a 0 return value indicates success. 66A -1 return value indicates an error, 67and an error code is stored in 68.Va errno . 69.Sh HISTORY 70The 71.Fn syscall 72function appeared in 73.Bx 4.0 . 74.Sh BUGS 75There is no way to simulate system calls that have multiple return values 76such as 77.Xr pipe 2 . 78