如何在 VIM 的命令行上指定“光标下的单词”？

<cword> is the word under the cursor (:help <cword>).

Sorry, I should have been more complete in this answer.

You can nmap a command to it, or this series of keystrokes for the lazy will work:

b #go to beginning of current word
yw #yank to register

Then, when you are typing in your pattern you can hit <control-r>0<enter> which will paste in your command the contents of the 0-th register.

You can also make a command for this like:

:nmap <leader>w :s/\(<c-r>=expand("<cword>")<cr>\)/

Which will map hitting '\' and 'w' at the same time to replace your command line with

:s/\(<currentword>\)/

You need to escape the backslashes within the mapping. You can also include the substitution string within the mapping.

:nmap <leader>w :s/\\(<c-r>=expand("<cword>")<cr>\\)/\\1\\1<cr>

ywPx

will do what you describe.

ywPxw

will also advance the cursor to the next word.

yiwP

yiw: Yank inner word (the word under the cursor). This command also moves the cursor to the beginning of the word.

P: Paste before the cursor.

You can then map the e.g.: < ALT > - D to this command:

:nmap < ALT >-D yiwP

Another easy way to do this is to use the * command.

In regular mode, when over a word, type

*:s//\0\0<Enter>

* makes the search pattern the current word (e.g. \<abc\>).

:s// does a substitution using the current search pattern, and \0 in the replacement section is the matched string.

You can then repeat this behaviour, say over word "def", by either typing the same again, or by typing

*@:

@: just repeats the last ex command, without a need for an <Enter>, in this case the substitution.

You can also record a quick macro to do this using the q command

qd*:s//\0\0<Enter>q

Then repeat it to your hearts content by typing

@d

when over a word you want to double. As this is only one character less than the prior solution, it may not be worth it to you - unless you will be doing other ex-commands between the word-doubling, which would change the behaviour of @:

While in command-line mode, CTRL+R CTRL+W will insert the word under the cursor.

See the help for c_CTRL-R for a listing of all the other special registers:

:help c_CTRL-R

" count word  (case sensitive)
nmap <F4> :%s/\(<c-r>=expand("<cword>")<cr>\)//gn<cr>

@user11211 has the most straightforward way to duplicate the word under cursor:

yiwP

yank inner word (moves cursor to start of word), paste (before cursor).

eg. straigh[t]forward ----> straightforwar[d]straightforward

[] is cursor

To elaborate...

You probably want to have the cursor following your duplicated word:

yiwPea

straigh[t]forward ----> straightforwardstraightforward[]

NOTE:

yiw

is yank inner word (without whitespace)

yaw

is yank all word (including trailing whitespace).

yawPea

is therefore duplicate word including whitespace, and position cursor.

straigh[t]forward ----> straightforward straightforward[]