grab all the usernames in /etc/passwd
1cut -f1 -d: /etc/passwd
where field f1 is the first occurrence before delimiter :. Since the first occurrence is the username, the command above will grab all the usernames.
fyi, one entry in /etc/passwd looks like this:
jane:x:1000:1000:Jane,,,:/home/jane:/bin/bash
1cut -f7 -d: /etc/passwd
Field 7 is the last part in /etc/passwd, i.e, the shell associated with each account.
-d, delimiter
-f, field