How to read a from a file while executing code

Question

Related config:

noremap <F5> :make<CR>
noremap <F6> :!./%<<CR>
noremap <F7> :!./%< 2>/dev/null<CR>

The problem is while running the program with F6 when I paste input from clipboard it messes up the output and before all the input is pasted there is already something printed which makes it a bit difficult to read quickly.

A workaround is to read from a file, like ./<filename> < in but i was not able to map this command to key.

noremap <F8> :!./%<CR> < in

I am a beginner and don't know much about these configurations. Any help will be appreciated.

Edit:
For copy pasting from clipboard, i have the following lines in .vimrc from https://stackoverflow.com/questions/44480829/how-to-copy-to-clipboard-in-vim-of-bash-on-windows. I am using WSL on windows.

vmap <C-c> y:new ~/.vimbuffer<CR>VGp:x<CR> \| :!cat ~/.vimbuffer \| clip.exe <CR><CR>
map <C-Shift-v> :r ~/.vimbuffer<CR>

Answer 1

You can't do it with map, you should do it with command, command allows you to input filename as args.

command -nargs=1 -complete=file Exe !./%< <<args>

:h <args> will be expanded to your input filename. You can execute it like this:

:Exe input_filename

If you are using vim8, you may try this:

command -nargs=1 -complete=file ExeTerminal exec 'terminal bash -c "./%< <<args>"' | wincmd p

It's asynchronous, you output will be in a vim terminal buffer. :h terminal see | as it's arguments, you need to use exec to write multiple commands in 1 line.

update

If you want to create a map to just enter filename:

nnoremap <f8> :Exe<space>

<space> is a space.