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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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.\" 4. 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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