[unix-history] / share / man / man4 / fd.4

.\" Copyright (c) 1990, 1991 The Regents of the University of California.
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     @(#)fd.4	5.2 (Berkeley) 3/28/91
.\"
.Dd March 28, 1991
.Dt FD 4
.Os
.Sh NAME
.Nm fd ,
.Nm stdin ,
.Nm stdout ,
.Nm stderr
.Nd file descriptor files
.Sh DESCRIPTION
The files
.Pa /dev/fd/0
through
.Pa /dev/fd/#
refer to file descriptors which can be accessed through the file
system.
If the file descriptor is open and the mode the file is being opened
with is a subset of the mode of the existing descriptor, the call:
.Bd -literal -offset indent
fd = open("/dev/fd/0", mode);
.Ed
.Pp
and the call:
.Bd -literal -offset indent
fd = fcntl(0, F_DUPFD, 0);
.Ed
.Pp
are equivalent.
.Pp
Opening the files
.Pa /dev/stdin ,
.Pa /dev/stdout
and
.Pa /dev/stderr
is equivalent to the following calls:
.Bd -literal -offset indent
fd = fcntl(STDIN_FILENO,  F_DUPFD, 0);
fd = fcntl(STDOUT_FILENO, F_DUPFD, 0);
fd = fcntl(STDERR_FILENO, F_DUPFD, 0);
.Ed
.Pp
Flags to the
.Xr open 2
call other than
.Dv O_RDONLY , 
.Dv O_WRONLY
and
.Dv O_RDWR
are ignored.
.Sh FILES
.Bl -tag -width /dev/stderr -compact
.It Pa /dev/fd/#
.It Pa /dev/stdin
.It Pa /dev/stdout
.It Pa /dev/stderr
.El
.Sh SEE ALSO
.Xr tty 4
.Sh HISTORY
The
.Nm
descriptor implementation
.Ud
Commit	Line	Data
15637ed4 RG	1	.\" Copyright (c) 1990, 1991 The Regents of the University of California.
	2	.\" 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 5.2 (Berkeley) 3/28/91
	33	.\"
	34	.Dd March 28, 1991
	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
	44	The files
	45	.Pa /dev/fd/0
	46	through
	47	.Pa /dev/fd/#
	48	refer to file descriptors which can be accessed through the file
	49	system.
	50	If the file descriptor is open and the mode the file is being opened
	51	with is a subset of the mode of the existing descriptor, the call:
	52	.Bd -literal -offset indent
	53	fd = open("/dev/fd/0", mode);
	54	.Ed
	55	.Pp
	56	and the call:
	57	.Bd -literal -offset indent
	58	fd = fcntl(0, F_DUPFD, 0);
	59	.Ed
	60	.Pp
	61	are equivalent.
	62	.Pp
	63	Opening the files
	64	.Pa /dev/stdin ,
65	.Pa /dev/stdout
66	and
67	.Pa /dev/stderr
68	is equivalent to the following calls:
69	.Bd -literal -offset indent
70	fd = fcntl(STDIN_FILENO, F_DUPFD, 0);
71	fd = fcntl(STDOUT_FILENO, F_DUPFD, 0);
72	fd = fcntl(STDERR_FILENO, F_DUPFD, 0);
73	.Ed
74	.Pp
75	Flags to the
76	.Xr open 2
77	call other than
78	.Dv O_RDONLY ,
79	.Dv O_WRONLY
80	and
81	.Dv O_RDWR
82	are 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	.Sh HISTORY
93	The
94	.Nm
95	descriptor implementation
96	.Ud