1.\" $OpenBSD: fd.4,v 1.4 2001/01/29 02:11:08 niklas Exp $ 2.\" $NetBSD: fd.4,v 1.3 1994/11/30 16:22:13 jtc Exp $ 3.\" 4.\" Copyright (c) 1990, 1991, 1993 5.\" The Regents of the University of California. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. All advertising materials mentioning features or use of this software 16.\" must display the following acknowledgement: 17.\" This product includes software developed by the University of 18.\" California, Berkeley and its contributors. 19.\" 4. Neither the name of the University nor the names of its contributors 20.\" may be used to endorse or promote products derived from this software 21.\" without specific prior written permission. 22.\" 23.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33.\" SUCH DAMAGE. 34.\" 35.\" @(#)fd.4 8.1 (Berkeley) 6/9/93 36.\" 37.Dd June 9, 1993 38.Dt FD 4 39.Os 40.Sh NAME 41.Nm fd , 42.Nm stdin , 43.Nm stdout , 44.Nm stderr 45.Nd file descriptor files 46.Sh DESCRIPTION 47The files 48.Pa /dev/fd/0 49through 50.Pa /dev/fd/# 51refer to file descriptors which can be accessed through the file system. 52If the file descriptor is open and the mode the file is being opened 53with is a subset of the mode of the existing descriptor, the call: 54.Bd -literal -offset indent 55fd = open("/dev/fd/0", mode); 56.Ed 57.Pp 58and the call: 59.Bd -literal -offset indent 60fd = fcntl(0, F_DUPFD, 0); 61.Ed 62.Pp 63are equivalent. 64.Pp 65Opening the files 66.Pa /dev/stdin , 67.Pa /dev/stdout , 68and 69.Pa /dev/stderr 70is equivalent to the following calls: 71.Bd -literal -offset indent 72fd = fcntl(STDIN_FILENO, F_DUPFD, 0); 73fd = fcntl(STDOUT_FILENO, F_DUPFD, 0); 74fd = fcntl(STDERR_FILENO, F_DUPFD, 0); 75.Ed 76.Pp 77Flags to the 78.Xr open 2 79call other than 80.Dv O_RDONLY , 81.Dv O_WRONLY , 82and 83.Dv O_RDWR 84are ignored. 85.Sh FILES 86.Bl -tag -width /dev/stderr -compact 87.It Pa /dev/fd/# 88.It Pa /dev/stdin 89.It Pa /dev/stdout 90.It Pa /dev/stderr 91.El 92.Sh SEE ALSO 93.Xr tty 4 94