2fe8fb192f
There is important information about booting non-ack images in docs/UPDATING. ack/aout-format images can't be built any more, and booting clang/ELF-format ones is a little different. Updating to the new boot monitor is recommended. Changes in this commit: . drop boot monitor -> allowing dropping ack support . facility to copy ELF boot files to /boot so that old boot monitor can still boot fairly easily, see UPDATING . no more ack-format libraries -> single-case libraries . some cleanup of OBJECT_FMT, COMPILER_TYPE, etc cases . drop several ack toolchain commands, but not all support commands (e.g. aal is gone but acksize is not yet). . a few libc files moved to netbsd libc dir . new /bin/date as minix date used code in libc/ . test compile fix . harmonize includes . /usr/lib is no longer special: without ack, /usr/lib plays no kind of special bootstrapping role any more and bootstrapping is done exclusively through packages, so releases depend even less on the state of the machine making them now. . rename nbsd_lib* to lib* . reduce mtree
138 lines
3.7 KiB
Groff
138 lines
3.7 KiB
Groff
.\" $NetBSD: dup.2,v 1.21 2009/01/11 02:46:30 christos Exp $
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.\"
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.\" Copyright (c) 1980, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)dup.2 8.1 (Berkeley) 6/4/93
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.\"
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.Dd December 2, 2008
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.Dt DUP 2
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.Os
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.Sh NAME
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.Nm dup ,
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.Nm dup2
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.Nd duplicate an existing file descriptor
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In unistd.h
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.Ft int
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.Fn dup "int oldd"
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.Ft int
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.Fn dup2 "int oldd" "int newd"
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.Sh DESCRIPTION
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.Fn dup
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duplicates an existing object descriptor and returns its value to
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the calling process
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.Fa ( newd
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=
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.Fn dup oldd ) .
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The argument
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.Fa oldd
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is a small non-negative integer index in
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the per-process descriptor table.
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The value must be less than the size of the table, which is returned by
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.Xr getdtablesize 3 .
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The new descriptor returned by the call
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is the lowest numbered descriptor currently not in use by the process.
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.Pp
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The object referenced by the descriptor does not distinguish
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between
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.Fa oldd
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and
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.Fa newd
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in any way.
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Thus if
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.Fa newd
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and
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.Fa oldd
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are duplicate references to an open
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file,
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.Xr read 2 ,
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.Xr write 2
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and
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.Xr lseek 2
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calls all move a single pointer into the file,
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and append mode, non-blocking I/O and asynchronous I/O options
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are shared between the references.
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If a separate pointer into the file is desired, a different
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object reference to the file must be obtained by issuing an
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additional
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.Xr open 2
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call.
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The close-on-exec flag on the new file descriptor is unset.
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.Pp
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In
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.Fn dup2 ,
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the value of the new descriptor
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.Fa newd
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is specified.
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If this descriptor is already
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in use, the descriptor is first deallocated as if a
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.Xr close 2
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call had been done first.
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If
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.Fa newd
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and
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.Fa oldd
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are the same, the call has no effect.
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.Sh RETURN VALUES
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The value \-1 is returned if an error occurs in either call.
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The external variable
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.Va errno
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indicates the cause of the error.
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.Sh ERRORS
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.Fn dup
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and
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.Fn dup2
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fail if:
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.Bl -tag -width Er
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.It Bq Er EBADF
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.Fa oldd
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is not a valid active descriptor
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or
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.Fa newd
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is not in the range of valid file descriptors.
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.It Bq Er EMFILE
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Too many descriptors are active.
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.El
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.Sh SEE ALSO
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.Xr accept 2 ,
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.Xr close 2 ,
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.Xr fcntl 2 ,
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.Xr open 2 ,
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.Xr pipe 2 ,
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.Xr socket 2 ,
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.Xr socketpair 2 ,
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.Xr getdtablesize 3
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.Sh STANDARDS
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The
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.Fn dup
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and
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.Fn dup2
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functions conform to
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.St -p1003.1-90 .
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