Lua 5.3 came with a nice UTF-8 support library internally boundled. This is that same library packaged as a standalone library, which can be used by any version of Lua (5.1, 5.2 and LuaJIT).
On Unix systems or using a Make-like interface simply run
sudo make
sudo make install
For more information on how to customize the building procedure, check both makefiles (at root and src)
You can also grab a rock!
luarocks install lutf8
local utf8 = require "utf8"Check the Lua Manual for information
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