I have been given this project by my OS doctor I have no experience with LINUX nor UNIX and I do not know where to start
Create a new file shell.c (or shell.cpp if you prefer C++). This will be our main shell program that will execute commands from a command line. Our shell should intepret the following built-in commands:
cd: changes the current working directory
pwd: prints the current working directory
echo: prints a message and the values of environment variables
exit: terminates the shell
env: prints the current values of the environment variables
setenv: sets an environment variable
To implement the first task we will need to write a "parser" program that parse a line and tokenize it into separate words. This program includes a routine tokenize to split up a command line into an array of strings (tokens), We need this array to match and interpret the command (first array element) and its arguments (the rest of the array). You can do a simple search on "parsers.c" or "parser.cpp" on the internet and you will find some to use or help you writing you own parser.
Add the main routine, the tokenize, and interpret functions to your shell.c program. The intepret function must be extended to implement the built-in commands.