chfn changes user fullname, office number, office extension, and home phone number information for a user's account. This information is typically printed by finger(1) and similiar programs. A normal user may only change the fields for their own account, the super user may change the fields for any account. Also, only the super user may use the -o option to change the undefined portions of the GCOS field.
The only restrictions placed on the contents of the fields is that no control characters may be present, nor any of comma, colon, or equal sign. The other field does not have this restriction, and is used to store accounting information used by other applications.
If none of the options are selected, chfn operates in an interactive fashion, prompting the user with the current values for all of the fields. Enter the new value to change the field, or leave the line blank to use the current value. The current value is displayed between a pair of [? marks. Without options, chfn prompts for the current user account.