#!/usr/bin/lua
--[[
abs2rel for Lua
split and split_path taken from "Split a string with a pattern, Take Two"
http://lua-users.org/wiki/SplitJoin
--]]
function split(str, pat)
local t = {} -- NOTE: use {n = 0} in Lua-5.0
local fpat = "(.-)" .. pat
local last_end = 1
local s, e, cap = str:find(fpat, 1)
while s do
if s ~= 1 or cap ~= "" then
table.insert(t,cap)
end
last_end = e+1
s, e, cap = str:find(fpat, last_end)
end
if last_end <= #str then
cap = str:sub(last_end)
table.insert(t, cap)
end
return t
end
function split_path(str)
return split(str,'[\\/]+')
end
-- parts = split_path("/usr/local/bin")
--> {'usr','local','bin'}
function join(words, sep)
local s = ""
for i,v in ipairs(words) do
s = s .. sep .. v
end
return string.sub (s, string.len(sep)+1)
end
function abs2rel(path, base)
if path == base then return "." end
local pathdirs = split_path(path)
local basedirs = split_path(base)
local i = 1
local rem_i = math.min(#pathdirs, #basedirs)
-- remove common parts of both paths
while (rem_i > 0) and (pathdirs[i] == basedirs[i]) do
rem_i = rem_i - 1
table.remove(pathdirs, 1)
table.remove(basedirs, 1)
end
-- now for each remaining basedirs, replace them with ..
if #basedirs > 0 then
for i, v in ipairs(basedirs) do
basedirs[i] = ".."
end
end
for i, v in ipairs(pathdirs) do
basedirs[#basedirs+1] = v
end
return join(basedirs, "/")
end
if #arg ~= 2 then
io.stderr:write("usage: " .. arg[0] .. " <PATH> <BASE>\n")
os.exit(1)
end
print(abs2rel(arg[1], arg[2]))
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