Getting The Title From Html Files

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This example program prints out the titles of all HTML files passed to it on the command-line. It provides a rough example of parsing out data from HTML files. It it not necessarily robust though (e.g. consider the rare case of a comment line containing <!-- <title>ack</title> -->).

Usage example (from the shell):

$ ls *.html
cgi.html          htaccess.html  mod_include.html   urlmapping.html
configuring.html  mod_auth.html  mod_rewrite.html
core.html         mod_cgi.html   rewriteguide.html
$ ./title.lua *.html
cgi.html: Apache Tutorial: Dynamic Content with CGI
configuring.html: Configuration Files
core.html: Apache Core Features
htaccess.html: Apache Tutorial: .htaccess files
mod_auth.html: Apache module mod_auth
mod_cgi.html: Apache module mod_cgi
mod_include.html: Apache module mod_include
mod_rewrite.html: Apache module mod_rewrite
rewriteguide.html: Apache 1.3 URL Rewriting Guide
urlmapping.html: Mapping URLs to Filesystem Locations - Apache HTTP Server

Below is the Lua program title.lua:

#!/usr/bin/env lua

function getTitle(fname)
  local fp = io.open(fname, "r")
  if fp == nil then
    return false
  end

  -- Read up to 8KB (avoid problems when trying to parse /dev/urandom)
  local s = fp:read(8192)
  fp:close()

  -- Remove optional spaces from the tags.
  s = string.gsub(s, "\n", " ")
  s = string.gsub(s, " *< *", "<")
  s = string.gsub(s, " *> *", ">")

  -- Put all the tags in lowercase.
  s = string.gsub(s, "(<[^ >]+)", string.lower)

  local i, f, t = string.find(s, "<title>(.+)</title>")
  return t or ""
end

if arg[1] == nil then
  print("Usage: lua " .. arg[0] .. " <filename> [...]")
  os.exit(1)
end

i = 1
while arg[i] do
  t = getTitle(arg[i])
  if t then
    print(arg[i] .. ": " .. t)
  else
    print(arg[i] .. ": File opening error.")
  end
  i = i + 1
end
os.exit(0)

-- AlexandreErwinIttner

Alternatively, the [lua-gumbo] library can be used:

#!/usr/bin/env lua

local gumbo = require "gumbo"
local document = assert(gumbo.parseFile(arg[1] or io.stdin))
print(document.title)

In this case, both the HTML5 parser and the Document.title implementation fully conform to the spec and should produce the exact same result as a modern browser.

lua-gumbo is available via: luarocks install gumbo


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Last edited July 21, 2017 6:20 pm GMT (diff)