How do I programmatically set a register's content or pre-load a macro using setreg()?

Explanation

The setreg() VimScript function lets you populate any register with arbitrary content directly from the command line or a script — no recording required. This is especially useful for loading complex macros from your vimrc, resetting registers in scripts, or constructing macros dynamically.

How it works

• setreg('{reg}', '{content}') assigns the string {content} to register {reg}.
• The content is interpreted as keystrokes when the register is executed with @{reg}.
• An optional third argument controls the register type: 'c' for characterwise, 'l' for linewise, 'b' for blockwise.
• Special keys use the same notation as in macros: \<CR> for Enter, \<Esc> for Escape, \<C-a> for Ctrl+A.

Example

To load a macro that deletes a blank line and moves to the next:

:call setreg('q', 'dd')

Now @q will execute dd. For a more complex example, pre-load it in your vimrc:

" Macro to append a semicolon to the end of a line
call setreg('s', 'A;\<Esc>')

Then :source $MYVIMRC and @s appends ; to any line.

Tips

• Use getreg('q') to inspect the current content of a register.
• To clear a register: :call setreg('q', '').
• To reset register q before appending in a loop: qaq in normal mode also clears it, but setreg is scriptable.
• Combine with :let @q = '...' (the assignment form) for a cleaner vimrc syntax:

  let @q = 'A;\<Esc>'