writing pexpect like program in c++ on Linux

Is there any way of writing pexpect like small program which can launch a process and pass 开发者_C百科the password to that process? I don't want to install and use pexpect python library but want to know the logic behind it so that using linux system apis I can build something similar.

You could just use "expect". It is very light weight and is made to do what youre describing.

For very simple cases, empty is one option. It's a lightweight C program, and it can be used straight from a shell script and doesn't require Tcl.

For Debian/Ubuntu, the package is empty-expect.