RunSlashCmd

Thanks to cladhaire and Josh_Borke for all the effort in coming up with this code that allows you to pass a /command to wow from a lua script. The following code is cladhaire's final product

function RunSlashCmd(cmd)
  local slash,rest = cmd:match("^(%S+)%s*(.-)$")
  for name in pairs(SlashCmdList) do
     local i = 1
     local slashCmd
     repeat
        slashCmd = getglobal("SLASH_"..name..i)
        
        if slashCmd == slash then
           -- Call the handler
           SlashCmdList[name](rest)
           return true
        end
        i = i + 1
     until slashCmd == nil
  end
  return false
end 

RunSlashCmd("/help")

RunSlashCmd("/addon do this")

Try

local t={}; t.GetText = function(self) return self.text end; local function RunSlash(slash) t.text = slash; ChatEdit_ParseText(t) end

Alternative

Another method to accomplish the same effect is to insert the command into an editbox and send the command. Note that it's usually better to do this with your own EditBox to avoid taint or conflicts with user input into the default editbox.

-- Create our editbox (may not need a name, untested)
local editbox = CreateFrame("EditBox", "myEditBox", UIParent, "ChatFrameEditBoxTemplate")

editbox:SetText("/command here") 
ChatEdit_SendText(editbox)