add-include-guards.lua: Quick and dirty script to add include guards to header files

add-include-guards.lua

#!/usr/bin/lua

-- Quick and dirty script to add include guards to header files
-- Author: Alexandre Erwin Ittner <alexandre (a) ittner x com x br>
-- License: GPLv2 or (at your option) any later version

local io = require("io")
local table = require("table")
local os = require("os")

local function process_one_file(fname)
    if fname:sub(-2) ~= ".h" then
        io.stderr:write(fname, ": does not end in '.h'\n")
        return false
    end
    local fp = io.open(fname, "rb")
    if not fp then
        io.stderr:write(fname, ": failed to read file.\n")
        return false
    end
    local macroname = "_" .. fname:upper():gsub("[^A-Z0-9]", "_")
    local guard = "\n#ifndef " .. macroname .. "\n"
                .. "#define " .. macroname
    local tbl = { }
    local added = false
    while true do
        local line = fp:read("*l")
        if not line then break end
        if line:find(macroname) then
            io.stderr:write(fname, ": looks that this file already have ",
                "the guard in the line '", line, "'.\n")
            fp:close()
            return false
        end
        tbl[#tbl+1] = line
        if not added and line:gsub("%s", "") == "" then
            tbl[#tbl+1] = guard
            added = true
        end
    end
    if not added then
        table.insert(tbl, guard, 1)
    end
    tbl[#tbl+1] = "\n#endif  /* " .. macroname .. " */\n"
    fp:close()

    local fp = io.open(fname, "wb")
    if not fp then
        io.stderr:write(fname, ": failed to update file.\n")
        return false
    end
    fp:write(table.concat(tbl, "\n"))
    if not fp:close() then
        io.stderr:write(fname, ": failed to close file.\n")
        return false
    end
    return true
end

if not arg or #arg < 1 then
    io.stderr:write("Usage: ", arg[0], " someheader.h [...]\n")
    os.exit(1)
end

local allok = true
for i = 1, #arg do
    allok = process_one_file(arg[i]) and allok
end
os.exit(allok and 0 or 1)

how do we use this?