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1.\" $NetBSD: fd.4,v 1.3 1994/11/30 16:22:13 jtc Exp $
2.\"
3.\" Copyright (c) 1990, 1991, 1993
4.\" The Regents of the University of California. All rights reserved.
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34.\" @(#)fd.4 8.1 (Berkeley) 6/9/93
35.\"
36.Dd June 9, 1993
37.Dt FD 4
38.Os
39.Sh NAME
40.Nm fd ,
41.Nm stdin ,
42.Nm stdout ,
43.Nm stderr
44.Nd file descriptor files
45.Sh DESCRIPTION
46The files
47.Pa /dev/fd/0
48through
49.Pa /dev/fd/#
50refer to file descriptors which can be accessed through the file
51system.
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