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

As David pointed out, setfperm() is the way to do this within vim.

Here are the mappings I use to add write or execute permissions to the current file:

function! ChmodPlus(expr, pat)
    let file = expand('%')
    let oldperms = getfperm(file)
    let newperms = substitute(oldperms, a:expr, a:pat, '')
    if (oldperms != newperms)
        call setfperm(file, newperms)
    endif
    echom(printf('Permissions: %s', newperms))
endfunction

function! ChmodPlusX()
    call ChmodPlus('^\(..\).', '\1x')
endfunction

function! ChmodPlusW()
    call ChmodPlus('^\(.\).', '\1w')
endfunction

" Make current file writeable
noremap  W :call ChmodPlusW()

" Make current file executable
noremap  X :call ChmodPlusX()