Important: this is a Fan Update to Cirk's popular addon, which fixes several compatibility issues with patch 5.0.4.
Lootcounter is a relatively small addon that aims to do two simple things - it tells you how many of something you have when you loot more of them, and it keeps track of the items you have on each character so that you can search for items through a small set of slash commands.
Lootcounter's slash commands
Lootcounter supports the following options: /lootcounter on enables Lootcounter for the current character (the default). /lootcounter off disables Lootcounter for the current character. /lootcounter ui on tells Lootcounter to show loot messages and counts in the middle of your screen, a bit like they would show for quest items. /lootcounter ui off tells Lootcounter to only show loot messages and counts in the usual chat window (the default). /lootcounter compact tells Lootcounter to try and compact any stacks of items you have (doesn't move stacks that are already complete though). /lootcounter show [searchterm] shows you a list of all your items (on you, and in the bank) that match the search term and their total counts in the default chat window. The search term can be part of an item name, an item type, or even an item link. /lootcounter showbank [searchterm] does the same thing as /lootcounter show but only shows matches in your bank. /lootcounter showbag [searchterm] does the same thing as /lootcounter show but only shows matches in your current bags or inventory. /lootcounter showalt <charactername> [searchterm] does the same thing as /lootcounter show but for the named alternate character. /lootcounter showall <searchterm> does the same thing as /lootcounter show but searches through all your characters at once. /lootcounter reset [charactername] resets the stored data for either your current, or the named character. /lootcounter resetall resets the stored data for all your characters. /lootcounter data on turns on storing of information for the current character (which is the default). /lootcounter data off turns off the storing of information for the current character - you might want to do this if you use another addon that provides a similar feature. /lootcounter status shows Lootcounter's status.
You can also just use /lc for these slash commands, unless you have Ybe's LootCount addon enabled, in which case Lootcounter will play nice and not register itself for the /lootcount or /lc slash commands (since those are what LootCount uses).
If you are using Cirk's Lootvalue, Lootcounter can provide count information for items directly to Lootvalue, so you can see them in your mouseover tooltips, without having to use lootcounter's slash commands.