Who
From MUME
Syntax: who [<group>] [alphabetically|number]
Lists the people currently in the game (although some people may choose to remain unseen).
Available groups:
ainur dwarves heroes men pray stoor bears elf hill metamorphs rangers tales beornings elves hobbits mortals retired tarkhnarb black eriadorian istari mountain rohirrim testchars cave fallohid legends newbies scouts thieves clerics females mages noldor shamans trolls dúnadan half-elves magic-users númenóreans silvan valar dúnedain halflings males orcs sindar warriors dwarf harfoot man players songs zaugurz
If you specify "number", you will not get the actual listing, but just the total number of players (in that group).
If you specify "alphabetically" (or some abbreviation longer than "al"), the players will be listed alphabetically. By default they are listed by how long they have been logged in (longest last).
Members of enemy races (for example Elves and Trolls) are unable to see each other with this command. Members of races who cooperate from time to time (Dwarves and Bears, Trolls and Tarkhnarb Orcs) can only see each other if they belong to the same group.