How do I complete keywords using only the current buffer as the source?

Explanation

<C-x><C-n> triggers keyword completion that searches only the current buffer for matches, scanning forward from the cursor. This is a sub-mode of Vim's <C-x> completion family, distinct from the plain <C-n> which consults all sources listed in the complete option (other open buffers, included files, tags, etc.).

How it works

• In insert mode, type a partial word and press <C-x><C-n> to complete from the current buffer only (forward scan)
• <C-x><C-p> does the same but searches backward through the buffer
• Once the menu is open, <C-n> and <C-p> cycle through the current-buffer matches

Example

You have this function at the top of your file:

function processConnectionTimeout() {

Later in the same file you type processCo and press <C-x><C-n>:

processConnectionTimeout

Only words from the current buffer are offered, ignoring all other open files.

Tips

• Use <C-x><C-n> when you want fast, predictable completions scoped to the file you are editing, without noise from unrelated buffers
• For completion from all open buffers (the default <C-n> behavior), omit the <C-x> prefix
• Other useful <C-x> sub-modes: <C-x><C-l> (whole lines), <C-x><C-f> (file paths), <C-x><C-]> (tags)
• The full list of <C-x> sub-modes is documented at :help ins-completion