1.\" Copyright (c) 1990, 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.\" @(#)fd.4 8.1 (Berkeley) 6/9/93 29.\" $FreeBSD: src/share/man/man4/fd.4,v 1.5.2.1 2001/07/21 09:16:46 schweikh Exp $ 30.\" $DragonFly: src/share/man/man4/fd.4,v 1.2 2003/06/17 04:36:59 dillon Exp $ 31.\" 32.Dd June 9, 1993 33.Dt FD 4 34.Os 35.Sh NAME 36.Nm fd , 37.Nm stdin , 38.Nm stdout , 39.Nm stderr 40.Nd file descriptor files 41.Sh DESCRIPTION 42The files 43.Pa /dev/fd/0 44through 45.Pa /dev/fd/# 46refer to file descriptors which can be accessed through the file 47system. 48If the file descriptor is open and the mode the file is being opened 49with is a subset of the mode of the existing descriptor, the call: 50.Bd -literal -offset indent 51fd = open("/dev/fd/0", mode); 52.Ed 53.Pp 54and the call: 55.Bd -literal -offset indent 56fd = fcntl(0, F_DUPFD, 0); 57.Ed 58.Pp 59are equivalent. 60.Pp 61Opening the files 62.Pa /dev/stdin , 63.Pa /dev/stdout 64and 65.Pa /dev/stderr 66is equivalent to the following calls: 67.Bd -literal -offset indent 68fd = fcntl(STDIN_FILENO, F_DUPFD, 0); 69fd = fcntl(STDOUT_FILENO, F_DUPFD, 0); 70fd = fcntl(STDERR_FILENO, F_DUPFD, 0); 71.Ed 72.Pp 73Flags to the 74.Xr open 2 75call other than 76.Dv O_RDONLY , 77.Dv O_WRONLY 78and 79.Dv O_RDWR 80are ignored. 81.Sh FILES 82.Bl -tag -width /dev/stderr -compact 83.It Pa /dev/fd/# 84.It Pa /dev/stdin 85.It Pa /dev/stdout 86.It Pa /dev/stderr 87.El 88.Sh SEE ALSO 89.Xr tty 4 90