" Pattern to detect real-looking shebang to an absolute path
let s:shebang = '^#!\s*/[^/]\+'
" If the buffer looks shebanged, and the file being saved to doesn't exist
" yet, set up a hook to make it executable after the write is done done
function! shebang_create_exec#(filename) abort
" If the first line isn't a shebang, or the file exists, do nothing
if getline(1) !~# s:shebang || filereadable(a:filename)
return
endif
" Set a buffer variable to the target filename
let b:shebang_create_exec_filename = a:filename
" Set up a hook to run and clean up after the write
autocmd shebang_create_exec BufWritePost <buffer>
\ call s:Run(expand('<afile>:p'))
endfunction
" Clear away the hook that called us and make the file executable
function! s:Run(filename) abort
" Clear away the hook that called us
autocmd! shebang_create_exec BufWritePost <buffer>
" Check that the save filename was set by BufWritePre
if !exists('b:shebang_create_exec_filename')
return
endif
" Check that it matches the file we just saved, and if so, make that file
" executable
if a:filename ==# b:shebang_create_exec_filename
call s:MakeExecutable(b:shebang_create_exec_filename)
endif
" Clear away the save filename, even if we didn't change any permissions
unlet b:shebang_create_exec_filename
endfunction
" Make a given filename executable
function! s:MakeExecutable(filename) abort
" Get filename into local variable
let filename = a:filename
" How we do this depends on whether we have native file permissions
" functions (Vim >=8.0)
if exists('*setfperm')
" We have setfperm(), so we can make the file executable without a fork to
" chmod(1), which should be quick and safe
let cperm = getfperm(filename)
" Replace every third character of the permissions string with an 'x'
let nperm
\ = strpart(cperm, 0, 2).'x'
\ . strpart(cperm, 3, 2).'x'
\ . strpart(cperm, 6, 2).'x'
" If our new permissions string differs from the current one, apply it to
" the file
if nperm !=# cperm
call setfperm(filename, nperm)
endif
else
" We'll need to fork to chmod(1); escape the filename safely, using
" shellescape() if we've got it, or manual UNIX sh quoting if not
let filename_escaped = exists('*shellescape')
\ ? shellescape(filename)
\ : "'" . substitute(filename, "'", "'\\''", 'g') . "'"
" Try to make the file executable with a fork to chmod(1)
call system('chmod +x '.filename_escaped)
endif
endfunction
