Extend the shell implementation in xv$6($sh$.$c$)$ so that all commands entered by the user are

logged to a file called sh$\_$history.

$$ The commands should be logged into the file before they are executed.

$$ If sh$\_$history does not exist, your program is responsible for creating it$.$

$$ When extending shell implementation, you can only add new statements. You should not

modify the existing shell functionality.

$$ When xv$6$ is re$-$booted, the previous command history can be either kept or cleared.

Write a program called history.c$.$ This program will read from sh$\_$history and display the history

of the commands.

Sample run: