BASH LIKE TERMINAL USING C

1. Display requirement:

Username using 'getlogin'
Hostname using 'gethostname'
Current directory using 'getcwd'

2. Built-in commands:

cd: using 'chdir'
pwd: using 'getcwd'
echo: using 'printf'

3. ls command:

used 'strtok' to get arguments
used 'opendir' to open a directory using 'while' loop
used 'stat' command to get file info
used 'printf' to display details

4. System commands:

used 'fork' to start a new process
fg: parent waits for child to execute using 'wait' command
bg: parent does not wait
used 'execvp' to execute system commands

5. pinfo:

if no pid is given replace 'pid' with 'self'
read file '/proc/pid/stat' for pid, status and virtual
	memory used.
read the link to file '/proc/pid/exe' to get executable.

6. Finished bg processes:

maintained an array of all bg started processes.
after executing all commands everytime checking if the
	process exists or not by opening '/proc/pid' directory.
printing the exited processes using 'printf'

7. Bonus:

dirty:
	used 'execvp' to implement 'watch' command
	opened '/proc/meminfo' to read the dirty memory.

interrupt:
	used 'execvp' to implement 'watch' command
	opened '/proc/interrupts' to read the CPU usage by
		the keyboard interrupt.