5

I'm using Lua on iOS and I'm having problems to open a file with io.open("filename.txt","w"), I know that I'm receiving nil, but is there any way to detect the failure reason and try to solve it according to that? something like errno of C?

Hola Soy Edu Feliz Navidad
  • 6,746
  • 4
  • 38
  • 55

1 Answers1

10

From the documentation:

io.open (filename [, mode])

This function opens a file, in the mode specified in the string mode. It returns a new file handle, or, in case of errors, nil plus an error message.

An example usage using the second value returned from the function is as follows:

local f, err = io.open("filename.txt", "w")
if f then
    -- do something with f
else
    print("Error opening file: " .. err)
end

If the process does not have permission to open the file, for example, the following message will be printed out:

Error opening file: filename.txt: Permission denied

Community
  • 1
  • 1
  • I'd like to add that it is *very* important to check the return value of `io.open` before writing anything to the file; actually, if it returns `nil` and you pass this `nil` value as file handle for writing, Lua5.2 segfaults. – michaelmeyer Feb 12 '14 at 22:39