84d9c625bf
- Fix for possible unset uid/gid in toproto
- Fix for default mtree style
- Update libelf
- Importing libexecinfo
- Resynchronize GCC, mpc, gmp, mpfr
- build.sh: Replace params with show-params.
This has been done as the make target has been renamed in the same
way, while a new target named params has been added. This new
target generates a file containing all the parameters, instead of
printing it on the console.
- Update test48 with new etc/services (Fix by Ben Gras <ben@minix3.org)
get getservbyport() out of the inner loop
Change-Id: Ie6ad5226fa2621ff9f0dee8782ea48f9443d2091
178 lines
4.8 KiB
Groff
178 lines
4.8 KiB
Groff
.\" $NetBSD: readlink.2,v 1.32 2013/07/29 11:49:31 wiz Exp $
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.\"
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.\" 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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.\"
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.Dd July 28, 2013
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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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.Fn readlinkat "int fd" "const char * restrict path" "char * restrict buf"\
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"size_t bufsiz"
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.Sh DESCRIPTION
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.Fn readlink
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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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.Fn readlink
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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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.Fn readlinkat
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works the same way as
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.Fn readlink
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except if
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.Fa path
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is relative.
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In that case, it is looked up from a directory whose file
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descriptor was passed as
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.Fa fd .
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Search permission is required on this directory.
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.\" (These alternatives await a decision about the semantics of O_SEARCH)
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.\" Search permission is required on this directory
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.\" except if
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.\" .Fa fd
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.\" was opened with the
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.\" .Dv O_SEARCH
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.\" flag.
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.\" - or -
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.\" This file descriptor must have been opened with the
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.\" .Dv O_SEARCH
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.\" flag.
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.Fa fd
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can be set to
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.Dv AT_FDCWD
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in order to specify the current directory.
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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 EXAMPLES
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A typical use is illustrated in the following piece of code
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which reads the contents of a symbolic link named
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.Pa /symbolic/link
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and stores them as null-terminated string:
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.Bd -literal -offset indent
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#include \*[Lt]limits.h\*[Gt]
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#include \*[Lt]unistd.h\*[Gt]
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char buf[PATH_MAX];
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ssize_t len;
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if ((len = readlink("/symbolic/link", buf, sizeof(buf)-1)) == -1)
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error handling;
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buf[len] = '\e0';
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.Ed
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.Sh ERRORS
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.Fn readlink
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and
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.Fn readlinkat
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will fail if:
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.Bl -tag -width Er
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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 EFAULT
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.Fa buf
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extends outside the process's allocated address space.
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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 ELOOP
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Too many symbolic links were encountered in translating the pathname.
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.It Bq Er ENAMETOOLONG
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A component of a pathname exceeded
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.Brq Dv NAME_MAX
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characters, or an entire path name exceeded
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.Brq Dv PATH_MAX
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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 ENOTDIR
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A component of the path prefix is not a directory.
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.El
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.Pp
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In addition,
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.Fn readlinkat
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will fail if:
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.Bl -tag -width Er
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.It Bq Er EBADF
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.Fa path
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does not specify 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 valid file descriptor open for reading or searching.
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.It Bq Er ENOTDIR
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.Fa path
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is not an absolute path and
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.Fa fd
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is a file descriptor associated with a non-directory file.
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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 readlink
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function conforms to
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.St -p1003.1-2001 .
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.Fn readlinkat
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conforms to
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.St -p1003.1-2008 .
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.Sh HISTORY
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The
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.Fn readlink
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function appeared in
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.Bx 4.2 .
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The type returned was changed from
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.Ft int
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to
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.Ft ssize_t
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in
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.Nx 2.1 .
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