Delete all files except in array in NodeMCU Lua - arrays

Question

Delete all files except the files in array
files = {"init.lua", "client.lua", "config.htm", "server.lua", "update.lua"}

Answer 1

As mentioned in the documentation, you can get a list of all the files on the filesystem using file.list().
This returns a map file name => file size; so the filename is the table key, which you can make use of.
Keep in mind that:
Table indexing in Lua is acceptably fast
Key-Value pairs can be removed by setting the value to nil
So we can do something like this:
local whitelist = {"init.lua", "client.lua", "config.htm", "server.lua", "update.lua"}
local files = file.list()
-- Remove files found in the whitelist
for _, filename in ipairs(whitelist) do
files[filename] = nil
end
-- Delete the remaining files
for filename in pairs(files) do
file.remove(filename)
end

Answer 2

Firstly, we can create 3 array-like tables: one for the protected files (the one you provided), another to list all files in the directory and the last to select the files we will delete.
local protected = {"init.lua", "client.lua", "config.htm", "server.lua", "update.lua"}
local found = {}
local delete = {}
Next, we will gather the directory contents:
for name in io.popen([[dir "" /b]]):lines() do
table.insert(found, name)
end
It is worth noticing that it will get folders too, but it doesn't matter here, since we won't be able to delete these anyway.
Now, with a simple function and a for-loop we will get the values from found to delete except for the ones in protected:
local function contains(t, v)
for index, value in ipairs(t) do
if value == v then
return true
end
end
return false
end
for _, value in ipairs(found) do
if not contains(protected, value) then
table.insert(delete, value)
end
end
Now we delete the files in delete
for _, filename in ipairs(delete) do
print("Deleting "..filename.." (unless it is a folder)")
os.remove(filename) -- this function is simply unable to delete folders
end
And this is it. I must admit, I'm running it on Windows, so I used the dir command. Where you want to run it may need it to be changed to ls (from io.popen([[dir "" /b]]):lines() to io.popen([[ls "" /b]]):lines()).