My bash prompt

.bash_prompt.lua

local ret_code , n_jobs = ...
ret_code = tonumber ( ret_code )
n_jobs   = tonumber ( n_jobs ) or 0

local ffi = require "ffi"
ffi.cdef [[
	typedef uint32_t uid_t;
	uid_t geteuid(void);
	int gethostname(char *name, size_t namelen);
	char *getcwd(char *buf, size_t size);
	void free(void *ptr);
]]
local HOST_NAME_MAX = 64
local function gethostname ( )
	local buff = ffi.new ( "char[?]" , HOST_NAME_MAX )
	assert ( ffi.C.gethostname ( buff , HOST_NAME_MAX ) == 0 )
	return ffi.string ( buff )
end
local function getcwd ( )
	local cwd = ffi.C.getcwd ( nil , 0 )
	local str = ffi.string ( cwd )
	ffi.C.free ( cwd )
	return str
end

local getenv = os.getenv
local function cmd ( c )
	local fd = io.popen ( c .. " 2> /dev/null" )
	local ret = fd:read "*l"
	fd:close ( )
	return ret
end

local uid      = ffi.C.geteuid()
local hostname = getenv "HOSTNAME" or gethostname()
local username = getenv "USER" or getenv "USERNAME" or ""
local home     = getenv "HOME" or getenv "HOMEPATH"
local pwd      = (getenv "PWD" or getcwd()):gsub("^"..home,"~")

local escapes = {
	reset   = 0 ;
	bold    = 1 ;
	blink   = 5 ;
	fraktur = 20 ;

	-- Colours
	black   = 30 ;
	red     = 31 ;
	green   = 32 ;
	yellow  = 33 ;
	blue    = 34 ;
	magenta = 35 ;
	cyan    = 36 ;
	white   = 37 ;
}

-- \1 and \2 are undocumented features that cause bash to not count the characters inbetween as printable
-- (and hence will place the prompt at the correct location)
local function esc ( ... )
	return "\1\27["..table.concat({...},";").."m\2"
end
local function set_title ( str )
	io.write ( "\1\27]0;" , str , "\7\2" )
end

--set_title ( string.format ( "%s@%s %s" , username , hostname , pwd ) )

io.write (
	esc(escapes.yellow),os.date("%m-%d %H:%M:%S "),
	esc(escapes.reset,escapes.bold),username,
	esc(escapes.reset),"@",
	esc(escapes.green),hostname," ",
	esc(escapes.bold,escapes.blue),pwd,
	esc(escapes.reset)," "
)

local is_git = select(3, os.execute ( "git rev-parse --git-dir > /dev/null 2> /dev/null" )) == 0
if is_git then
	local hash = cmd "git show --format=%h"
	if hash then -- Hash is nil if currently not on a commit (e.g. new repo)
		local status = io.popen "git status -sb"
		local branch = status:read"*l":match("^## (.*)") -- First line is ## BRANCH NAME
		local dirty  = status:read"*l" -- If there are any uncommited changes they will follow
		status:close()
		local col = escapes.green
		if dirty then
			col = escapes.red
		end
		io.write(esc(col),"git:{",branch,":",hash,"} ")
	else
		io.write(esc(escapes.green),"git ")
	end
end

local is_hg = select(3, os.execute ( "hg root > /dev/null 2> /dev/null" )) == 0
if is_hg then
	local t = { }
	local summary = io.popen "hg summary"
	for line in  summary:lines() do
		local name , value = line:match("([^:]+): (.*)")
		if name then
			t [ name ] = value
		end
	end
	summary:close()
	local col = escapes.green
	local hg_status = cmd ( "hg status -q" )
	if hg_status then
		col = escapes.red
	elseif not t.update:match("(current)") then
		col = escapes.yellow
	end
	io.write(esc(col),"hg:{",t.branch,":",t.parent:match(":(%x*)"),"} ")
end

if n_jobs ~= 0 then
	io.write(esc(escapes.bold,escapes.cyan),n_jobs," jobs ")
end

io.write (esc(escapes.reset))

if ret_code and ret_code ~= 0 then
	io.write(esc(escapes.bold,escapes.red),"exit=",ret_code," ")
end

io.write ( uid==0 and "#" or "$" , " ", esc(escapes.reset) ) -- Reset

.bashrc

PS1="\$(luajit ~/.bash_prompt.lua \$? \j)"