readlinkat(2) - NetBSD Manual Pages

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READLINK(2)               NetBSD 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 suc-
     ceeds, 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 sys-
                        tem.

     [ELOOP]            Too many symbolic links were encountered in translat-
                        ing the pathname.

     [ENAMETOOLONG]     A component of a pathname exceeded {NAME_MAX} charac-
                        ters, or an entire path name exceeded {PATH_MAX} char-
                        acters.

     [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 nei-
                        ther AT_FDCWD nor a valid file descriptor open for
                        reading or searching.

     [ENOTDIR]          path is not an absolute path and fd is a file descrip-
                        tor 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.

NetBSD 10.1                      July 28, 2013                     NetBSD 10.1