* libs/libc/unistd/lib_readlinkat.c
*
* SPDX-License-Identifier: Apache-2.0
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
* Included Files
****************************************************************************/
#include <errno.h>
#include <unistd.h>
#include "libc.h"
#ifdef CONFIG_FS_LINKS
* Public Functions
****************************************************************************/
* Name: readlinkat
*
* Description:
* The readlinkat() system call operates in exactly the same way as
* readlink(), except for the differences described here.
*
* If the pathname given in pathname is relative, then it is interpreted
* relative to the directory referred to by the file descriptor dirfd
* (rather than relative to the current working directory of the calling
* process)
*
* If pathname is relative and dirfd is the special value AT_FDCWD, then
* pathname is interpreted relative to the current working directory of
* the calling process (like readlink()).
*
* If pathname is absolute, then dirfd is ignored.
*
* Input Parameters:
* dirfd - The file descriptor of directory.
* path - The full path to the symbolic link
* buf - The user-provided buffer in which to return the path to the
* link target.
* bufsize - The size of 'buf'
*
* Returned Value:
* Upon successful completion, readlinkat() will return the count of bytes
* placed in the buffer. Otherwise, it will return a value of -1, leave the
* buffer unchanged, and set errno to indicate the error.
*
****************************************************************************/
ssize_t readlinkat(int dirfd, FAR const char *path, FAR char *buf,
size_t bufsize)
{
FAR char *fullpath;
int ret;
fullpath = lib_get_tempbuffer(PATH_MAX);
if (fullpath == NULL)
{
set_errno(ENOMEM);
return ERROR;
}
ret = lib_getfullpath(dirfd, path, fullpath, PATH_MAX);
if (ret < 0)
{
lib_put_tempbuffer(fullpath);
set_errno(-ret);
return ERROR;
}
ret = readlink(fullpath, buf, bufsize);
lib_put_tempbuffer(fullpath);
return ret;
}
#endif