How to create an alias for a command in Vim?

Question

To leave completion untouched, try using

cnoreabbrev W w

It will replace W in command line with w, but only if it is neither followed nor preceded by word character, so :W<CR> will be replaced with :w<CR>, but :Write won’t. (Note that this affects any commands that match, including ones that you might not expect. For example, the command :saveas W Z will be replaced by :saveas w Z, so be careful with this.)

Update

Here is how I would write it now:

cnoreabbrev <expr> W ((getcmdtype() is# ':' && getcmdline() is# 'W')?('w'):('W'))

As a function:

fun! SetupCommandAlias(from, to)
  exec 'cnoreabbrev <expr> '.a:from
        \ .' ((getcmdtype() is# ":" && getcmdline() is# "'.a:from.'")'
        \ .'? ("'.a:to.'") : ("'.a:from.'"))'
endfun
call SetupCommandAlias("W","w")

This checks that the command type is : and the command is W, so it’s safer than just cnoreabbrev W w.

With supplementary searching, I've found that someone asked nearly the same question as I.

:command <AliasName> <string of command to be aliased>

will do the trick.

Please be aware that, as Richo points out, the user command must begin with a capital letter.

I find that mapping the ; key to : would be a better solution, and would make you more productive for typing other commands.

nnoremap ; :
vnoremap ; :

The best solution involves writing a custom function for handling abbreviations that only take place in the beginning of the command bar.

For this, add the following your vimrc file or anywhere else.

" cabs - less stupidity                                                      {{{
fu! Single_quote(str)
  return "'" . substitute(copy(a:str), "'", "''", 'g') . "'"
endfu
fu! Cabbrev(key, value)
  exe printf('cabbrev <expr> %s (getcmdtype() == ":" && getcmdpos() <= %d) ? %s : %s',
    \ a:key, 1+len(a:key), Single_quote(a:value), Single_quote(a:key))
endfu
"}}}

 

" use this custom function for cabbrevations. This makes sure that they only
" apply in the beginning of a command. Else we might end up with stuff like
"   :%s/\vfoo/\v/\vbar/
" if we happen to move backwards in the pattern.

" For example:
call Cabbrev('W', 'w')

A few useful abbreviations from the source material where I found this stuff:

call Cabbrev('/',   '/\v')
call Cabbrev('?',   '?\v')

call Cabbrev('s/',  's/\v')
call Cabbrev('%s/', '%s/\v')

call Cabbrev('s#',  's#\v')
call Cabbrev('%s#', '%s#\v')

call Cabbrev('s@',  's@\v')
call Cabbrev('%s@', '%s@\v')

call Cabbrev('s!',  's!\v')
call Cabbrev('%s!', '%s!\v')

call Cabbrev('s%',  's%\v')
call Cabbrev('%s%', '%s%\v')

call Cabbrev("'<,'>s/", "'<,'>s/\v")
call Cabbrev("'<,'>s#", "'<,'>s#\v")
call Cabbrev("'<,'>s@", "'<,'>s@\v")
call Cabbrev("'<,'>s!", "'<,'>s!\v")