Write a C program that sorts the environment variables passed to the program based on environment variable names. In the class, you were shown with a program printing out all the environment variables passed to the program. Each environment variable has a variable name (the part before the '=' sign) and the a variable value (the part after the '=' sign). For example, the following three entries in envp (i.e., three environment variables), the names are USER, PWD, and HOME, respectively, and the values are ubuntu, /tmp, and /home/ubuntu.

envp[5] = "USER=ubuntu"

envp[6] = "PWD=/tmp"

envp[7] = "HOME=/home/ubuntu"

Your program needs to sort the environment variables. You can directly sort the environment variables by exchanging the pointers saved in envp. You may also choose to create another data structure of your choice (e.g., another array of pointers, or linked list). But, no matter which method you choose, your program must print out the environment variables, including their names and values, in ascending order determined by applying strcmp() on their names.

For example, the three entries above are sorted by calling strcmp() to compare USER, PWD, and HOME. Since the strcmp() calls determine that "HOME" < "PWD" and "PWD"<"USER", your program should print out

HOME=/home/ubuntu

PWD=/tmp

USER=ubuntu