Passing line number from vim to external command

Question

I am using VIM and I would like to pass the current line number to an external program.

something like this: map <F3> :!mycmd <linenumber><CR>

I tried to substitute <linenumber> for line('.'), line("."), . and others, but nothing seems to work. Thanks.

Answer 1

You must use :execute to use a variable or expression in your mapping:

nnoremap <F3> :execute ":!echo " . line('.')<CR>