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. 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.\" @(#)fd.4 8.1 (Berkeley) 6/9/93 33.\" 34.Dd June 9, 1993 35.Dt FD 4 36.Os 37.Sh NAME 38.Nm fd , 39.Nm stdin , 40.Nm stdout , 41.Nm stderr 42.Nd file descriptor files 43.Sh DESCRIPTION 44The files 45.Pa /dev/fd/0 46through 47.Pa /dev/fd/# 48refer to file descriptors which can be accessed through the file 49system. 50If the file descriptor is open and the mode the file is being opened 51with is a subset of the mode of the existing descriptor, the call: 52.Bd -literal -offset indent 53fd = open("/dev/fd/0", mode); 54.Ed 55.Pp 56and the call: 57.Bd -literal -offset indent 58fd = fcntl(0, F_DUPFD, 0); 59.Ed 60.Pp 61are equivalent. 62.Pp 63Opening the files 64.Pa /dev/stdin , 65.Pa /dev/stdout 66and 67.Pa /dev/stderr 68is equivalent to the following calls: 69.Bd -literal -offset indent 70fd = fcntl(STDIN_FILENO, F_DUPFD, 0); 71fd = fcntl(STDOUT_FILENO, F_DUPFD, 0); 72fd = fcntl(STDERR_FILENO, F_DUPFD, 0); 73.Ed 74.Pp 75Flags to the 76.Xr open 2 77call other than 78.Dv O_RDONLY , 79.Dv O_WRONLY 80and 81.Dv O_RDWR 82are ignored. 83.Sh FILES 84.Bl -tag -width /dev/stderr -compact 85.It Pa /dev/fd/# 86.It Pa /dev/stdin 87.It Pa /dev/stdout 88.It Pa /dev/stderr 89.El 90.Sh SEE ALSO 91.Xr tty 4 92