NAME

readlink, readlinkat — read value of a symbolic link

LIBRARY

Standard C Library (libc, -lc)

SYNOPSIS

#include <unistd.h>

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

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

DESCRIPTION

readlink() 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.

readlinkat() works the same way as readlink() except if path is relative. In that case, it is looked up from a directory whose file descriptor was passed as fd. Search permission is required on this directory. fd can be set to AT_FDCWD in order to specify the current directory.

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.

EXAMPLES

A typical use is illustrated in the following piece of code which reads the contents of a symbolic link named /symbolic/link and stores them as null-terminated string:

#include <limits.h> 
#include <unistd.h> 
 
char buf[PATH_MAX]; 
ssize_t len; 
 
if ((len = readlink("/symbolic/link", buf, sizeof(buf)-1)) == -1) 
	error handling; 
buf[len] = '\0';

ERRORS

readlink() and readlinkat() will fail if:

[EACCES]

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

[EFAULT]

buf extends outside the process's allocated address space.

[EINVAL]

The named file is not a symbolic link.

[EIO]

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

[ELOOP]

Too many symbolic links were encountered in translating the pathname.

[ENAMETOOLONG]

A component of a pathname exceeded {NAME_MAX} characters, or an entire path name exceeded {PATH_MAX} characters.

[ENOENT]

The named file does not exist.

[ENOTDIR]

A component of the path prefix is not a directory.

In addition, readlinkat() will fail if:

[EBADF]

path does not specify an absolute path and fd is neither AT_FDCWD nor a valid file descriptor open for reading or searching.

[ENOTDIR]

path is not an absolute path and fd is a file descriptor associated with a non-directory file.

SEE ALSO

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

STANDARDS

The readlink() function conforms to IEEE Std 1003.1-2001 (“POSIX.1”). readlinkat() conforms to IEEE Std 1003.1-2008 (“POSIX.1”).

HISTORY

The readlink() function appeared in 4.2BSD. The type returned was changed from int to ssize_t in NetBSD 2.1.