Lua how to remove ".html" text from end of string

Question

So I have a string in Lua and I want to remove all occurances ".html" text of the end of the string

local lol = ".com/url/path/stuff.html"

print(lol)

Output i want :

.com/url/path/stuff


local lol2 = ".com/url/path/stuff.html.html"

print(lol2)

Output i want :

.com/url/path/stuff

bar = lol:gsub("(.*).html.*$","%1") removes one occurance of the .html text but as the "lol2" variable string example i provided it does not work on that :( — C0nw0nk
– C0nw0nk, Commented Aug 16, 2018 at 1:18

brianolive · Accepted Answer · 2018-08-16 10:01:04Z

4

First, you could define a function like this:

function removeHtmlExtensions(s)
    return s:gsub("%.html", "")
end

Then:

local lol = ".com/url/path/stuff.html"
local lol2 = ".com/url/path/stuff.html.html"

local path1 = removeHtmlExtensions(lol)
local path2 = removeHtmlExtensions(lol2)

print(path1) -- .com/url/path/stuff
print(path2) -- .com/url/path/stuff

There is a second value returned from the gsub method that indicates how many times the pattern was matched. It returns, for example, 1 with path1 and 2 with path2. (Just in case that info is useful to you):

local path2, occurrences = removeHtmlExtensions(lol2)

print(occurrences) -- 2

edited Aug 16, 2018 at 10:01

answered Aug 16, 2018 at 1:32

brianolive

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4 Comments

C0nw0nk Over a year ago

Is this also ok i got this to work too. bar = lol:gsub(".html.*$","") print(bar) the only issue is if the url contains /html/ it removes that too more problems :(

Curtis Fenner Over a year ago

Since . is a special character in string patterns, you should escape it when you pass to :gsub as :gsub("%.html", "")

brianolive Over a year ago

@Curtis, right, of course. Thanks for the fix. Updated.

DarkWiiPlayer Over a year ago

that will remove all occurrences of '.html' though

DarkWiiPlayer · Accepted Answer · 2018-08-17 06:21:15Z

2

This can easily be done with a tail-recursive function like this:

local function foo(bar)
  if bar:find('%.html$') then return foo(bar:sub(1, -5) else return bar end
end

in words:

If bar ends in '.html', remove the last 5 characters and feed that into foo again (to remove any more occurrences)
Otherwise, return bar as it is

Benefits:

Tail recursive, so it can't overflow the stack even for very long chains '.html'
string.find is pretty fast when you anchor the search to the end of the string with $
string.sub is also rather fast compared to, for example, string.gsub (note that those two do completely different things, despite the similar name).

answered Aug 17, 2018 at 6:21

DarkWiiPlayer

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