how can fzf save output into a file without using redirect?

[haolian9]

i had went through the manual, and did not found an option like --output;

in some case it's impossible to read fzf's stdout, for example, in nvim :terminal a output file is necessary;
but fzf > filerequires a shell, this overhead can be avoid if fzf takes over this job.

[haolian9]

i managed to do it in a fork