READLINK(2) | System Calls Manual | READLINK(2)

# 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.

July 28, 2013 | NetBSD 8.2