module(..., package.seeall)

require("posix")

-- the following methods are available:
-- /proc/<pid>/stat	the comm field (2nd) field contains name but only up 
--   			to 15 chars. does not resolve links
--
-- /proc/<pid>/cmdline	argv[0] contains the command. However if it is a script
--   			then will the interpreter show up
--
-- /proc/<pid>/exe	link to exe file. this will resolv links
--
-- returns list of all pids for given exe name

--[[
-- gives lots of false positives for busybox
local function is_exe(path, name)
	local f = posix.readlink(path.."/exe")
	if f and (f == name or posix.basename(f) == name) then
		return true
	else
		return false
	end
end
]]--


local function is_stat(path, name)
	local f = io.open(path.."/stat")
	local line = f:read()
	local p = string.match(line, "^%d+ %((%d+)%)")
	f:close()
	if p ~= nil and string.len(name) <= 15 and p == name then
		return true
	else
		return false
	end
end

local function is_cmdline(path, name)
	local f = io.open(path.."/cmdline")
	if f == nil then
		return false
	end
	local line = f:read()
	f:close()
	if line == nil then 
		return false
	end
	local arg0 = string.gsub(line, string.char(0)..".*", "")
	return posix.basename(arg0) == name
end

function pidof(name)
	local pids = {}
	local i, j

	for i,j in pairs(posix.glob("/proc/[0-9]*")) do
		local pid = tonumber(posix.basename(j))
		if is_stat(j, name) or is_cmdline(j, name) then
			table.insert(pids, pid)
		end
	end
	if #pids == 0 then
		pids = nil
	end
	return pids
end