fingerdaemon project from final chapter of Haskell Book
Pre the public internet era, the finger service was a way to figure out how to contact colleagues or other people on the same computer network and whether they were on the network at a given time. finger was originally intended to be used to share an office number, email address and basic contact details.
The fingerdaemon (a daemon is a process that runs in the background) acts as a simple server for a finger client where data is stored in a SQLite database (instead of on the OS) and returns information on a user.
The project is built using stack, a tool to build Haskell projects and manage dependencies (instructions on installing can be found here).
Clone the repo and run stack build to install the dependencies and build the executables.
Debug is a basic echo server to test the connection. To run it:
> sudo `stack exec which debug`
Type in a message and it should echo the message back.
This sets up the SQLite database.
A user has the following fields:
username
shell (e.g. /bin/zsh)
homeDirectory (e.g. /Users/Andrew)
realName
phone
- create the database with:
stack exec dbuser -- init - add a user with:
stack exec dbuser -- add username shell homeDirectory realName phone - update a user with:
stack exec dbuser -- update username shell homeDirectory realName phone - show all users with
stack exec dbuser -- all
After setting up the database run the fingerdaemon with
> sudo `stack exec which fingerdaemon`
in another shell session you can type
> finger andrew@localhost
if that user exists in the db it will send back the user details for that user