Lua Pattern Matching to "fix" html code

Question

I have a lot of badly formatted HTML which I am trying to fix using Lua for example

<p class='heading'>my useful information</p>
<p class='body'>lots more text</p>

which I want to replace with

<h2>my useful information</h2>
<p class='body'>lots more text</p>

What I am trying to use is the following Lua function which is passed the whole html page. How ever I have two problems, I want the gsub to pass the replace function the whole match including the top and tail and I will then replace the top and tails and return the string. The other problem is my inner replace function can't see the top and tail fields.

Sorry if this is an obvious one, but I am still learning Lua.

function topandtailreplace(str,top,tail,newtop,newtail)
local strsearch = top..'(.*)'..tail
     function replace(str)
            str = string.gsub(str,top,newtop)
            str = string.gsub(str,tail,newtail)
            return str
    end
    local newstr = str:gsub(strsearch,replace())
    return newstr
end

lhf · Accepted Answer · 2011-06-16 16:55:42Z

3

This seems to work:

s=[[
<p class='heading'>my useful information</p>
<p class='body'>lots more text</p>
]]

s=s:gsub("<p class='heading'>(.-)</p>","<h2>%1</h2>")
print(s)

answered Jun 16, 2011 at 16:55

lhf

72.9k11 gold badges117 silver badges162 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Jane T Over a year ago

Thanks very much, I had gone off trying to make it harder than it was, I completely missed the %1 option to retain the middle bit.

Craig Barnes · Accepted Answer · 2017-08-16 07:16:26Z

0

You could use a HTML parsing library with a DOM tree, for example lua-gumbo:

luarocks install gumbo

The following example would do what you want:

local gumbo = require "gumbo"

local input = [[
    <p class='heading'>my useful information</p>
    <p class='body'>lots more text</p>
]]

local document = assert(gumbo.parse(input))
local headings = assert(document:getElementsByClassName("heading"))
local heading1 = assert(headings[1])
local textnode = assert(heading1.childNodes[1])
local new_h2 = assert(document:createElement("h2"))

heading1.parentNode:insertBefore(new_h2, heading1)
new_h2:appendChild(textnode)
heading1:remove()

io.write(document:serialize(), "\n")

answered Aug 16, 2017 at 7:16

Craig Barnes

1328 bronze badges

Collectives™ on Stack Overflow

Lua Pattern Matching to "fix" html code

2 Answers 2

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related