Login Information

We have a user who is working off site and we would like to know
that he is actually logging into the system, what he is working on,
and when he logs out. I found the profile file in the /etc directory and
placed a "cat" command to copy the information of any users logging
onto the server into another file but when I done this it just copied the
information of the profile file into my other file rather than information
on
the user logging in??

Does anyone have any suggestions on how to get information of users
logging into the server and copy it into another file???

Cheers
Colin