Lua return directory path from path

Question

I have string variable which represents the full path of some file, like:

x = "/home/user/.local/share/app/some_file" on Linux
or
x = "C:\\Program Files\\app\\some_file" on Windows

I'm wondering if there is some programmatic way, better then splitting string manually to get to directory path

How do I return directory path (path without filename) in Lua, without loading additional library like LFS, as I'm using Lua extension from other application?

Answer 1

In plain Lua, there is no better way. Lua has nothing working on paths. You'll have to use pattern matching. This is all in the line of the mentality of offering tools to do much, but refusing to include functions that can be replaced with one-liners:

-- onelined version ;)
--    getPath=function(str,sep)sep=sep or'/'return str:match("(.*"..sep..")")end
getPath=function(str,sep)
    sep=sep or'/'
    return str:match("(.*"..sep..")")
end

x = "/home/user/.local/share/app/some_file"
y = "C:\\Program Files\\app\\some_file"
print(getPath(x))
print(getPath(y,"\\"))

Answer 2

Here is a platform independent and simpler solution based on jpjacobs solution:

function getPath(str)
    return str:match("(.*[/\\])")
end

x = "/home/user/.local/share/app/some_file"
y = "C:\\Program Files\\app\\some_file"
print(getPath(x)) -- prints: /home/user/.local/share/app/
print(getPath(y)) -- prints: C:\Program Files\app\

Answer 3

For something like this, you can just write your own code. But there are also libraries in pure Lua that do this, like lua-path or Penlight.