How to change file permission from within vi

Question

I sometimes open a read-only file in vi, forgetting to do chmod +w before opening it. Is there way to change the file from within vi?

Something like !

Answer 1

Have you tried

!chmod +w %

The % represents the current filename.

You could also map a key to this like Ctrl-W.

:map  :!chmod +w %

Note that you type Ctrl-V Ctrl-M to get the