How to change read/write mode for a file using Emacs

emacsfilefile-permissions

If a file is set to read only mode, how do I change it to write mode and vice versa from within Emacs?

Best Solution

M-x toggle-read-only

or in more recent versions of Emacs

M-x read-only-mode

On my Windows box, that amounts to Alt-x to bring up the meta prompt and typing "toggle-read-only" to call the correct elisp function.

If you are using the default keyboard bindings,

C-x C-q

(which you read aloud as "Control-X Control-Q") will have the same effect. Remember, however, given that emacs is essentially infinitely re-configurable, your mileage may vary.

Following up from the commentary: you should note that the writeable status of the buffer does not change the writeable permission of the file. If you try to write out to a read only file, you'll see a confirmation message. However, if you own the file, you can write out your changes without changing the permissions on the file.

This is very convenient if you'd like to make a quick change to a file without having to go through the multiple steps of add write permission, write out changes, remove write permission. I tend to forget that last step, leaving potentially critical files open for accidental changes later on.