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I have written a script that run in WingFTP Server which has a Lua scripting engine built in. The script recursively deletes empty folders except the specified root folder.

--Walks a file tree and delete empty folders except the root folder
function EmptyFolderDeleter(options)
    local rootPath = options.path
    local path = options.path

    function walk(path)
        local currentPath = path

        --cycle through the current directory, walking directories
        for dir in c_GetDir(currentPath) do
            local fullPath = currentPath..dir.."/"
            walk(fullPath)
        end

        --if we've got this far then we're at the bottom of the tree
        --there are no more directories to visit
        --now check if there is ANYTHING (file or folder) in the current folder 
        local empty = true
        for isdir, file in c_GetFileDir(currentPath) do
            empty = false
        end

        --now check the 'empty' flag and if the folder is the root
        if empty == true and currentPath ~= rootPath then
            c_RemoveFileDir(currentPath)
        end

    end
    walk(path)
 end

The script uses three custom Lua functions that are built into WingFTP:

c_GetDir() = an iterator that returns directory names as string

c_GetFileDir() = an iterator that returns directory and file names as strings. Also returns a boolean whether the returned string is directory or not.

c_RemoveFileDir() = Deletes the specified file or folder

My script can be called like so like so:

local root = "D:/Clients/"
for dir in c_GetDir(root) do
    EmptyFolderDeleter{path=root..dir.."/"}
end

Is there is simpler or more efficient way to recursively delete empty sub folders in Lua?

Is there anything I can do to improve code readability?

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1 Answer 1

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Since you're not updating the variables path, rootPath and currentPath anywhere, use a single variable.

Define the function walk locally.

You can also break out of your c_GetFileDir loop once you've updated the empty flag. This will remove the time to iterate through all children of a directory.

The help pages for WFTPServer have a different return values for c_GetFileDir than yours!

function EmptyFolderDeleter( options )
    local root = options.path

    local walk = function( path )

        --cycle through the current directory, walking directories
        for dir in c_GetDir( path ) do
            walk( path..dir.."/" )
        end

        --if we've got this far then we're at the bottom of the tree
        --there are no more directories to visit
        --now check if there is ANYTHING (file or folder) in the current folder 
        local empty = true
        for isdir, file in c_GetFileDir( path ) do
            empty = false
            break
        end

        --now check the 'empty' flag and if the folder is the root
        if empty and path ~= root then
            c_RemoveFileDir( path )
        end
    end

    walk( root )
 end
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  • 2
    \$\begingroup\$ Regarding c_GetFileDir in the help pages: Yes I was scratching my head for ages and then I contacted WingFTP directly who confirmed that their help pages are in fact incorrect! \$\endgroup\$ Commented May 11, 2015 at 14:49
  • \$\begingroup\$ Thanks for your tips, I feel the readability of the code has been improved. Just one note: I like the the white spacing in the function parameters, e.g. walk( root ) I have not seen this before and am surprised that I quite like it! How do you format functions with multiple parameters? \$\endgroup\$ Commented May 12, 2015 at 7:29
  • 1
    \$\begingroup\$ @chazjn f( a, b, {1, 2, 3}, c, d ) \$\endgroup\$ Commented May 12, 2015 at 11:03

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