The AuthDigestGroupFile directive sets the name of a textual file containing the list of groups and their members (user names). Filename is the absolute path to the group file.
Each line of the group file contains a groupname followed by a colon, followed by the member usernames separated by spaces. Example:
mygroup: bob joe anne
Note that searching large text files is very inefficient.
Security: make sure that the AuthGroupFile is stored outside the document tree of the web-server; do not put it in the directory that it protects. Otherwise, clients will be able to download the AuthGroupFile.