fbbd9655e5
Renumber cluase 4 to 3, per what everybody else did when BSD granted them permission to remove clause 3. My insistance on keeping the same numbering for legal reasons is too pedantic, so give up on that point. Submitted by: Jan Schaumann <jschauma@stevens.edu> Pull Request: https://github.com/freebsd/freebsd/pull/96
159 lines
4.2 KiB
Groff
159 lines
4.2 KiB
Groff
.\" Copyright (c) 1983, 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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.\" @(#)readlink.2 8.1 (Berkeley) 6/4/93
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.\" $FreeBSD$
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.\"
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.Dd April 10, 2008
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.Dt READLINK 2
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.Os
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.Sh NAME
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.Nm readlink ,
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.Nm readlinkat
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.Nd read value of a symbolic link
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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 ssize_t
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.Fn readlink "const char *restrict path" "char *restrict buf" "size_t bufsiz"
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.Ft ssize_t
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.Fo readlinkat
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.Fa "int fd" "const char *restrict path" "char *restrict buf" "size_t bufsize"
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.Fc
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.Sh DESCRIPTION
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The
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.Fn readlink
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system call
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places the contents of the symbolic link
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.Fa path
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in the buffer
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.Fa buf ,
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which has size
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.Fa bufsiz .
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The
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.Fn readlink
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system call does not append a
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.Dv NUL
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character to
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.Fa buf .
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.Pp
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The
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.Fn readlinkat
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system call is equivalent to
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.Fn readlink
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except in the case where
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.Fa path
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specifies a relative path.
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In this case the symbolic link whose content is read relative to the
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directory associated with the file descriptor
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.Fa fd
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instead of the current working directory.
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If
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.Fn readlinkat
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is passed the special value
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.Dv AT_FDCWD
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in the
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.Fa fd
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parameter, the current working directory is used and the behavior is
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identical to a call to
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.Fn readlink .
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.Sh RETURN VALUES
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The call returns the count of characters placed in the buffer
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if it succeeds, or a \-1 if an error occurs, placing the error
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code in the global variable
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.Va errno .
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.Sh ERRORS
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The
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.Fn readlink
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system call
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will fail if:
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.Bl -tag -width Er
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.It Bq Er ENOTDIR
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A component of the path prefix is not a directory.
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.It Bq Er ENAMETOOLONG
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A component of a pathname exceeded 255 characters,
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or an entire path name exceeded 1023 characters.
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.It Bq Er ENOENT
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The named file does not exist.
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.It Bq Er EACCES
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Search permission is denied for a component of the path prefix.
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.It Bq Er ELOOP
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Too many symbolic links were encountered in translating the pathname.
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.It Bq Er EINVAL
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The named file is not a symbolic link.
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.It Bq Er EIO
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An I/O error occurred while reading from the file system.
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.It Bq Er EFAULT
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The
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.Fa buf
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argument
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extends outside the process's allocated address space.
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.El
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.Pp
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In addition to the errors returned by the
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.Fn readlink ,
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the
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.Fn readlinkat
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may fail if:
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.Bl -tag -width Er
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.It Bq Er EBADF
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The
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.Fa path
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argument does not specify an absolute path and the
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.Fa fd
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argument is neither
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.Dv AT_FDCWD
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nor a valid file descriptor open for searching.
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.It Bq Er ENOTDIR
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The
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.Fa path
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argument is not an absolute path and
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.Fa fd
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is neither
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.Dv AT_FDCWD
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nor a file descriptor associated with a directory.
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.El
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.Sh SEE ALSO
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.Xr lstat 2 ,
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.Xr stat 2 ,
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.Xr symlink 2 ,
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.Xr symlink 7
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.Sh STANDARDS
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The
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.Fn readlinkat
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system call follows The Open Group Extended API Set 2 specification.
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.Sh HISTORY
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The
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.Fn readlink
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system call appeared in
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.Bx 4.2 .
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The
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.Fn readlinkat
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system call appeared in
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.Fx 8.0 .
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