https://docs.mongodb.com/manual/tutorial/configure-ldap-sasl-openldap/

It would be helpful if the "Authenticate the user in the mongo shell" also included an example of authenticating by passing the command line options to the mongo shell. This is particularly useful so that the user does not have to type their password to appear on the screen.

Example:

mongo --port <port> --host <host> --authenticationMechanism PLAIN --authenticationDatabase '$external' -u <user> -p