What's the easiest way to get a user's full name on a Linux/POSIX system?

Question

I could grep through /etc/passwd but that seems onerous. \'finger\' isn\'t installed and I\'d like to avoid that dependency. This is for a program so it would be nice if there

Answer 1

The top two answers can be combined in one line:

getent passwd  | cut -d ':' -f 5 | cut -d ',' -f 1