How to enter a command for the running program in a bash script after starting the program?

Question

linux

How to execute a command in the program after launch? all in one bash script.

#!/bin/bash 
./soft_test
 #тут нужно выполнить команду для soft_test типа "start"

you also need the command to be entered three seconds after soft_test is launched

Answer 1

man expect

Answer 2

Try it printf 'start\n' | ./soft_test- without pause
If not, then there is a specialized expect utility .
https://habr.com/company/ruvds/blog/328436/

Answer 3

Sleep?
xdotool