readlink, readlinkat — read value of a symbolic link
Standard C Library (libc, −lc)
readlink(const char *restrict path, char *restrict buf, size_t bufsiz);
readlinkat(int fd, const char *restrict path, char *restrict buf, size_t bufsize);
The readlink() system call places the contents of the symbolic link path in the buffer buf, which has size bufsiz. The readlink() system call does not append a NUL character to buf.
The readlinkat() system call is equivalent to readlink() except in the case where path specifies a relative path. In this case the symbolic link whose content is read relative to the directory associated with the file descriptor fd instead of the current working directory. If readlinkat() is passed the special value AT_FDCWD in the fd parameter, the current working directory is used and the behavior is identical to a call to readlink().
The call returns the count of characters placed in the buffer if it succeeds, or a −1 if an error occurs, placing the error code in the global variable errno.
The readlink() system call will fail if:
A component of the path prefix is not a directory.
A component of a pathname exceeded 255 characters, or an entire path name exceeded 1023 characters.
The named file does not exist.
Search permission is denied for a component of the path prefix.
Too many symbolic links were encountered in translating the pathname.
The named file is not a symbolic link.
An I/O error occurred while reading from the file system.
The buf argument extends outside the process’s allocated address space.
In addition to the errors returned by the readlink(), the readlinkat() may fail if:
The path argument does not specify an absolute path and the fd argument is neither AT_FDCWD nor a valid file descriptor open for searching.
The path argument is not an absolute path and fd is neither AT_FDCWD nor a file descriptor associated with a directory.
The readlinkat() system call follows The Open Group Extended API Set 2 specification.
The readlink() system call appeared in 4.2BSD. The readlinkat() system call appeared in FreeBSD 8.0.
BSD April 10, 2008 BSD