How do I get login statistics?

Question

I want to get a list that shows how many times each user logged in to the system.

Something along the lines

user1 45
user2 134
user3 200

Answer 1

 last | cut -d' ' -f1 | sort | uniq -c | sort -rn

It'll output something like:

189 user1
 73 user2
    ...
  7 reboot
    ...
  1 wtmp
  1

When the username column contain 'reboot' it means system reboot, not a login. When the username column contain wtmp or it's empty it's also not a login.

Answer 2

last | cut -d' ' -f1| awk '{ users[$0]++ } END { for(w in users) { print users[w],w }}' | sort -n

Similar to dvb's answer but with awk.