NAME

readlink, readlinkat — read value of a symbolic link

SYNOPSIS

#include <unistd.h>

ssize_t
readlink(const char *restrict path, char *restrict buf, size_t bufsiz);

#include <fcntl.h>
#include <unistd.h>

ssize_t
readlinkat(int fd, const char *path, char *buf, size_t bufsiz);

DESCRIPTION

The readlink() function places the contents of the symbolic link path in the buffer buf, which has size bufsiz. readlink() does not append a NUL character to buf.

The readlinkat() function is equivalent to readlink() except that where path specifies a relative path, the symbolic link whose contents are read is determined relative to the directory associated with file descriptor fd instead of the current working directory.

If readlinkat() is passed the special value AT_FDCWD (defined in <fcntl.h>) in the fd parameter, the current working directory is used and the behavior is identical to a call to readlink().

RETURN VALUES

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.

ERRORS

readlink() and readlinkat() will fail if:

[ENOTDIR]

A component of the path prefix is not a directory.

[ENAMETOOLONG]

A component of a pathname exceeded NAME_MAX characters, or an entire pathname (including the terminating NUL) exceeded PATH_MAX bytes.

[ENOENT]

The named file does not exist.

[EACCES]

Search permission is denied for a component of the path prefix.

[ELOOP]

Too many symbolic links were encountered in translating the pathname.

[EINVAL]

The named file is not a symbolic link.

[EIO]

An I/O error occurred while reading from the file system.

[EFAULT]

buf or path extends outside the process's allocated address space.

Additionally, readlinkat() will fail if:

[EBADF]

The path argument specifies a relative path and the fd argument is neither AT_FDCWD nor a valid file descriptor.

[ENOTDIR]

The path argument specifies a relative path and the fd argument is a valid file descriptor but it does not reference a directory.

[EACCES]

The path argument specifies a relative path but search permission is denied for the directory which the fd file descriptor references.

SEE ALSO

lstat(2), stat(2), symlink(2), symlink(7)

STANDARDS

The readlink() and readlinkat() functions conform to IEEE Std 1003.1-2008 (“POSIX.1”).

HISTORY

The readlink() system call first appeared in 4.1cBSD. The readlinkat() system call has been available since OpenBSD 5.0.