From HowToGeek

Linux newusers Command Man Page

This is the man page for the newusers command.

NAME
       newusers - update and create new users in batch

SYNOPSIS
       newusers [new_users]

DESCRIPTION
       newusers reads a file of user name and clear-text password pairs and uses this 
       information to update a group of existing users or to create new users. Each line 
       is in the same format as the standard password file (see
       passwd(5)) with the following exceptions:

       pw_passwd
          This field will be encrypted and used as the new value of the encrypted password.

       pw_age
          This field will be ignored for shadow passwords if the user already exists.

       pw_gid
          This field may be the name of an existing group, in which case the named 
          user will be added as a member. If a non-existent numerical group is given, 
          a new group will be created having this number.

       pw_dir
          This field will be checked for existence as a directory and a new directory 
          with the same name will be created if it does not already exist. The 
          ownership of the directory will be set to be that of the user being created 
          or updated. Note that newusers does not create parent directories of the 
          new user's home directory. The newusers command will fail to create the 
          home directory if the parent directories do not exist, and will send a message 
          to stderr informing the user of the failure. The newusers command will not
          halt or return a failure to the calling shell if it fails to create the home 
          directory, it will continue to process the batch of new users specified.

       This command is intended to be used in a large system environment where 
       many accounts are updated at a single time.

CAVEATS
       The input file must be protected since it contains unencrypted passwords.