List of all users and groups

The tool you want is almost certainly dscl. The shortest way to do it was already pointed out:

$ dscl . list /users$ dscl . list /groups

If you want to output information about each user, though, use readall:

$ dscl . readall /users$ dscl . readall /groups

And if you need to programatically parse said information, use -plist to make your life easier:

$ dscl -plist . readall /users$ dscl -plist . readall /groups

Open Directory approach (from: http://rickcogley.blogspot.com/2008/11/listing-open-directory-users-on-os-x.html):

dscacheutil -q userdscacheutil -q group

Take each line from the respective output that starts with "name:" strip off the "name:" and you have your list.If you do not have dscacheutil, you can use the manual commands:

root# dscl localhost list /Local/Default/Usersroot# dscl localhost list /LDAPv3/127.0.0.1/Users

Old school approach for before Open Directory....(sigh):For list of users:

• Grab the /etc/passwd file from the system.
• Split it out by lines
• Split out each line based on ":"
• Take the first symbol for each line

For list of groups:

• Grab the /etc/group file from the system.
• Split it out by lines
• Split out each line based on ":"
• Take the first symbol for each line

Non-garbbled/no-tempfile commands:

# dscl . list /users# dscl . list /groups