如何在Ruby中获取文件模式？

Question

I'm new to ruby file IO. I have a function that takes a File parameter, and I need to make sure that the file is in read-only mode.

def myfunction(file)
    raise ArgumentError.new() unless file.kind_of?(File)

    #Assert that file is in read-only mode
end

Any help would be appreciated!

Answer 1

So all you need is 'make sure make sure that the file is in read-only mode', why not just set it as readonly with FileUtils.chmod .

Or if actually you just want to test if it is readonly, use File.writeable ?

Answer 2

If you don't need to raise an error, you can use reopen , I think something like:

file = file.reopen(file.path, "r")

I can't find a way to otherwise verify that there isn't a write stream, but here's a bit of a hack that will work. Although I don't like exception throwing being used in the expected path, you could use close_write :

begin
  file.close_write
  # you could actually raise an exception here if you want
  # since getting here means the file was originally opened for writing
rescue IOError
  # This error will be raised if the file was not opened for
  # writing, so this is actually the path we want
end

Answer 3

You can use file.readable? , which returns true or false.

Please check this link.