How to set the $ variable? in si program?

Question

linux

I am writing a shell. In the task, it is necessary that after each launch of other programs through my shell, the value of the $? variable is set. And what I don't understand is how to do it? Will the system itself set this variable or should I somehow write its value with handles?

Answer 1

$? is the exit status of the last program.
In C, it corresponds to the value returned by the main function. The normal termination of the program should return 0, each error usually corresponds to its own code.

Answer 2

exit 0 at the end of main()
exiting main causes the program to exit (generally). and the output value of main is placed in the status variable $?
https://man7.org/linux/man-pages/man1/bash.1.html Special Parameters

Answer 3

This variable will be set by the system itself.

Will. If you say. $? is the return code of the last executed command. The return code is set by calling exit()
man exit in general.