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+.\"
+.\" Copyright (c) 1993, Sun Microsystems, Inc. All Rights Reserved.
+.\" Copyright 1989 AT&T
+.\" Copyright 2021 Oxide Computer Company
+.\"
+.\" The contents of this file are subject to the terms of the
+.\" Common Development and Distribution License (the "License").
+.\" You may not use this file except in compliance with the License.
+.\"
+.\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+.\" or http://www.opensolaris.org/os/licensing.
+.\" See the License for the specific language governing permissions
+.\" and limitations under the License.
+.\"
+.\" When distributing Covered Code, include this CDDL HEADER in each
+.\" file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+.\" If applicable, add the following below this CDDL HEADER, with the
+.\" fields enclosed by brackets "[]" replaced with your own identifying
+.\" information: Portions Copyright [yyyy] [name of copyright owner]
+.\"
+.Dd July 3, 1990
+.Dt FD 4FS
+.Os
+.Sh NAME
+.Nm fd ,
+.Nm stdin ,
+.Nm stdout ,
+.Nm stderr
+.Nd file descriptor files
+.Sh DESCRIPTION
+These files, conventionally called
+.Pa /dev/fd/0 ,
+.Pa /dev/fd/1 ,
+.Pa /dev/fd/2 ,
+and so on, refer to files accessible through file descriptors.
+If file descriptor
+.Em n
+is open, these two system calls have the same
+effect:
+.Bd -literal -offset indent
+fd = open("/dev/fd/<n>", mode);
+fd = dup(n);
+.Ed
+.Pp
+On these files
+.Xr creat 2
+is equivalent to
+.Xr open 2 ,
+and
+.Fa mode
+is
+ignored.
+As with
+.Xr dup 2 ,
+subsequent reads or writes on
+.Em fd
+fail unless the original file descriptor allows the operations.
+.Pp
+For convenience in referring to standard input, standard output, and standard
+error, an additional set of names is provided:
+.Pa /dev/stdin
+is a synonym
+for
+.Pa /dev/fd/0 ,
+.Pa /dev/stdout
+for
+.Pa /dev/fd/1 ,
+and
+.Pa /dev/stderr
+for
+.Pa /dev/fd/2 .
+.Sh DIAGNOSTICS
+.Xr open 2
+returns
+.Sy -1
+and
+.Va errno
+is set to
+.Er EBADF
+if the associated file descriptor is not open.
+.Sh SEE ALSO
+.Xr creat 2 ,
+.Xr dup 2 ,
+.Xr open 2