pam_lua-based dynamic system motd.

motd.lua

#!/usr/bin/env lua
-- pam_lua-based dynamic MOTD.
-- Rewritten from scratch, again.
-- (Maybe also because it was a bit filthy...)
-- Still kinda bad, cause it executes programs...
-- But hey, it Works For Me(tm)!
--
-- To use:
-- Install pam_lua (https://github.com/vifino/pam_lua).
-- OPEN A ROOT SESSION RIGHT NOW. TMUX AS ROOT, TOO.
-- Add `session optional pam_lua.so script=/path/to/motd.lua` to some PAM file, like system or login.
-- Login and hope it works. In case it doesn't, revert the change, check system logs and tell me.

-- Configs
local OS = 'freebsd'
local filters = "box-unicode clippy"
local minlen = 40

-- Try not to fuck up anything after here.

-- Localize some functions
local tonumber, tostring = tonumber, tostring
local fmt = string.format
local min, max, floor, log = math.min, math.max, math.floor, math.log
local strep = string.rep
local popen = io.popen

-- Helpers
local function pad(str, n, c)
	c = c or ' '
	return str .. strep(c, n - #str)
end

local function sizefmt(s)
	local C = "B"
	
	if s >= 0x40000000 then
		s = s / 0x40000000
		C = "G"
	elseif s >= 0x100000 then
		s = s / 0x100000
		C = "M"
	elseif s >= 1024 then
		s = s / 0x400
		C = "K"
	end
	local d = 10 ^ (floor(log(s) / log(10)) - 2)
	return tostring(floor(s / d) * d)..C
end

local function exec(prog)
	local f = popen(prog)
	local c = f:read('*all')
	f:close()
	return c
end

local function oneexec(prog)
	local r = exec(prog)
	return r:match("^([^\r\n]+)")
end

-- Hacky way to parse sysctl. Yay.
local sysctl_pattern = "^([%w._-]) = (.-)$"
if OS == 'freebsd' then sysctl_pattern = "^([%w._-]+): (.-)$" end

local function sysctl_parse(sysctl)
	local cmd = 'sysctl -a'
	if sysctl then cmd = 'sysctl -- '.. sysctl end

	local res = {}

	local output = exec(cmd)
	local lastname
	for line in output:gmatch("[^\r\n]+") do
		local name, val = line:match(sysctl_pattern)
		if not val then
			res[lastname] = res[lastname] .. line .. '\n'
		else
			res[name] = val
			lastname = name
		end
	end
	return res
end

local sysctl = {}
setmetatable(sysctl, {__index=function(t, k)
	local vals = sysctl_parse(k)
	for nk, nv in pairs(vals) do
		local v = nv
		local numb = tonumber(nv)
		if numb then v = numb end
		rawset(t, nk, v)
	end
	return t[k] or true
end})

-- Content
local content={}
local function addl(...) content[#content+1] = fmt(...) end

-- Basics
local hostname = oneexec("hostname")
addl(os.date("%H:%M %p, %A, the %x."))

-- Uptime
local up, users = oneexec("uptime"):match("up +(.-), +([0-9]+) user")
addl("Uptime:   %s", up)
addl("Users:    %s users", users)

addl("")
-- Memory
local mem_used, mem_avail, mem_total
if OS == "freebsd" then
	mem_total = sysctl["hw.physmem"]
	mem_avail = (sysctl["vm.stats.vm.v_inactive_count"] + sysctl["vm.stats.vm.v_cache_count"] +
	             sysctl["vm.stats.vm.v_free_count"]
	            ) * sysctl["hw.pagesize"]
	mem_used = mem_total - mem_avail
else
	-- TODO: make it work on linux too.
end
addl("Memory:   %s/%s used (%.2f%%)", sizefmt(mem_used), sizefmt(mem_total), (mem_used/mem_total) * 100)

-- Formatting!
local formatters = {}
formatters.none = function(linet) return linet end

-- Boxes!!
-- UL, UR, DL, DR, BU, BD, BL, BR, HL, HR
local boxes = {
	plain =  {'+', '+',  '+',  '+', '-', '_', '|', '|', '[', ']'},
	curved = {'/', '\\', '\\', '/', '-', '_', '|', '|', '<', '>'},
	unicode = {'┌', '┐', '└', '┘', '─', '─', '│', '│', '<', '>'},
}

for name, C in pairs(boxes) do
	local C1, C2, C3, C4, C5, C6, C7, C8, C9, C10 = C[1], C[2], C[3], C[4], C[5], C[6], C[7], C[8], C[9], C[10]
	formatters["box-"..name] = function(linet)
		local maxn = max(#hostname + 3, minlen or 0)
		for i=1, #linet do
			maxn = max(maxn, #linet[i])
		end
	
		local rett = {
			[1] = C1 .. C5 .. C9 .. hostname .. C10 .. strep(C5, maxn - 3 - #hostname) .. C2
		}
		for i=1, #linet do
			local str = linet[i]
			rett[i+1] = C7 .. pad(str, maxn) .. C8
		end
		rett[#rett+1] = C3 .. strep(C6, maxn) .. C4
		return rett
	end
end

-- Ascii art stuffs. Mostly clippy.
local artsies = {}
artsies.clippy = [[
 __
/  \
|  |
|O O/
|| ||   /
|\_/|  /
\___/ <--
]]

for name, ascii in pairs(artsies) do
	local asciimax = 0
	local asciit = {}
	local n = 1
	for line in ascii:gmatch("[^\r\n]+") do
		asciimax = max(asciimax, #line)
		asciit[n] = line
		n = n + 1
	end
	local asciilen = n-1

	formatters[name] = function(linet)
		local outb = {}
		local numo = #linet
		local startpos = 1
		local offset = 0
		if numo < asciilen then
			offset = asciilen - numo
		elseif numo > asciilen then
			startpos = numo - asciilen + 1
		end
		local padding = strep(" ", asciimax)
		for i=1, max(numo + offset, startpos + asciilen) - 1 do
			local line = linet[i-offset] or ""
			if i >= startpos then
				outb[i] = pad(asciit[i - startpos + 1], asciimax) .. line
			else
				outb[i] = padding .. line
			end
		end
		return outb
	end
end

-- Output
local outt = content
for filter in filters:gmatch("[^ ]+") do
	outt = formatters[filter](outt)
end
local out = ""
for i=1, #outt do
	out = out .. outt[i] .. '\n'
end

if pam then
	if pam.handler == "open_session" then
		if pam.flag.silent then return pam.ret.ignore end
		pam.info(out)
	end
	return pam.ret.ignore
end

io.write(out)