Apache HTTP Server Version 2.4

htdigest is used to create and update the flat-files used
    to store usernames, realm and password for digest authentication of HTTP
    users. Resources available from the Apache HTTP server can be restricted
    to just the users listed in the files created by htdigest.
This manual page only lists the command line arguments. For details of
    the directives necessary to configure digest authentication in
    httpd see the Apache manual, which is part
    of the Apache distribution or can be found at
    http://httpd.apache.org/.
htdigest [ -c ]
    passwdfile realm username
-cpasswdfile-c is given, this file is created if it does not already
    exist, or deleted and recreated if it does exist.realmusernameThis program is not safe as a setuid executable. Do not make it setuid.