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READLINK(2) System Calls Manual READLINK(2)

readlink, readlinkat, freadlink — read value of a symbolic link

#include <unistd.h>

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

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

ssize_t
freadlink(int fd, char *restrict buf, size_t bufsize);

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

The () 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 () system call returns the same information about an open symbolic link file referenced by descriptor fd.

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.

readlink() will fail if:

[]
Search permission is denied for a component of the path prefix.
[]
Buf extends outside the process's allocated address space.
[]
The named file is not a symbolic link.
[]
An I/O error occurred while reading from the file system.
[]
Too many symbolic links are encountered in translating the pathname. This is taken to be indicative of a looping symbolic link.
[]
A component of a pathname exceeded {NAME_MAX} characters, or an entire path name (possibly expanded by a symbolic link) exceeded {PATH_MAX} characters.
[]
The named file does not exist.
[]
A component of the path prefix is not a directory.

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.

#include <unistd.h>

int
(const char *path, char *buf, int bufsize);;

The function type and the type of bufsize have changed.

lstat(2), stat(2), symlink(2), compat(5), symlink(7)

The readlinkat() system call is expected to conform to POSIX.1-2008 .

The readlink() function call appeared in 4.2BSD. The readlinkat() system call appeared in OS X 10.10. The freadlink() system call appeared in macOS 13.0.

June 4, 1993 BSD 4.2