How to get list of directories in Lua

Question

I need a list of directory in LUA

Suppose I have a directory path as "C:\\Program Files"

I need a list of all the folders in that particular path and

Answer 1

You also install and use the 'paths' module. Then you can easily do this as follow:

require 'paths'

currentPath = paths.cwd() -- Current working directory
folderNames = {}
for folderName in paths.files(currentPath) do
    if folderName:find('$') then
        table.insert(folderNames, paths.concat(currentPath, folderName))
    end
end

print (folderNames)

-- This will print all folder names

Optionally, you can also look for file names with a specific extension by replacing fileName:find('$') with fileName:find('txt' .. '$')

If you're running on a Unix-based machine you can get a numerically-sorted list of files using the following code:

thePath = '/home/Your_Directory'
local handle = assert(io.popen('ls -1v ' .. thePath)) 
local allFileNames = string.split(assert(handle:read('*a')), '\n')

print (allFileNames[1]) -- This will print the first file name

The second code also excludes files such as '.' and '..'. So it's good to go!

Answer 2

I don't like installing libraries either and am working on an embedded device with less memory power then a pc. I found out that using 'ls' command lead to an out of memory. So I created a function that uses 'find' to solve the problem.

This way it was possible to keep memory usage steady and loop all the 30k files.

function dirLookup(dir)
   local p = io.popen('find "'..dir..'" -type f')  --Open directory look for files, save data in p. By giving '-type f' as parameter, it returns all files.     
   for file in p:lines() do                         --Loop through all files
       print(file)       
   end
end

Answer 3

Few fixes of val says Reinstate Monica solution:

function scandir(directory)
    local pfile = assert(io.popen(("find '%s' -mindepth 1 -maxdepth 1 -type d -printf '%%f\\0'"):format(directory), 'r'))
    local list = pfile:read('*a')
    pfile:close()

    local folders = {}

    for filename in string.gmatch(list, '[^%z]+') do
        table.insert(folders, filename)
    end

    return folders
end

Now it filters by folders, excludes dir itself and prints only names.

Answer 4

 for dir in io.popen([[dir "C:\Program Files\" /b /ad]]):lines() do print(dir) end

*For Windows

Outputs:

Adobe
Bitcasa
Bonjour
Business Objects
Common Files
DVD Maker
IIS
Internet Explorer
iPod
iTunes
Java
Microsoft Device Emulator
Microsoft Help Viewer
Microsoft IntelliPoint
Microsoft IntelliType Pro
Microsoft Office
Microsoft SDKs
Microsoft Security Client
Microsoft SQL Server
Microsoft SQL Server Compact Edition
Microsoft Sync Framework
Microsoft Synchronization Services
Microsoft Visual Studio 10.0
Microsoft Visual Studio 9.0
Microsoft.NET
MSBuild
...

Each time through the loop you are given a new folder name. I chose to print it as an example.

Answer 5

IIRC, getting the directory listing isn't possible with stock Lua. You need to write some glue code yourself, or use LuaFileSystem. The latter is most likely the path of least resistance for you. A quick scan of the docs shows lfs.dir() which will provide you with an iterator you can use to get the directories you are looking for. At that point, you can then do your string comparison to get the specific directories you need.

Answer 6

Don't parse ls, it's evil! Use find with zero-terminated strings instead (on linux):

function scandir(directory)
    local i, t = 0, {}
    local pfile = assert(io.popen(("find '%s' -maxdepth 1 -print0"):format(directory), 'r'))
    local list = pfile:read('*a')
    pfile:close()
    for filename in s:gmatch('[^\0]+')
        i = i + 1
        t[i] = filename
    end
    return t
end

WARNING: however, as an acceped answer this apporach could be exploited if directory name contain ' in it. Only one safe solution is to use lfs or other special library.