-> fork() to create a child process to aid the parent process in completing task
-> waitpid() to wait for the child process to finish, so that parent can start working
-> execv() to pass arguments to executable binaries
-> The shell runs inside main() in a while loop.
-> First the user input is taken in raw form using read_command() method.
-> Then this entered command is passed to parse_command method which trims spaces from both sides, tokenize the command.
-> After calling parse_command(), we have tokens of the command which are used to run the command.
-> These tokens are sent to execute_command() method, in order to get executed.
-> The functions check if the first token is a vliad command or not.
-> Based on the outcomes, if the first token is a valid command, the coressponding method to execute it is called.
-> In the method, using the tokens, the complete argument set is extracted and ran within the fucntion in case of internal commands and using the dedicated executables in case of external commands
-> Every External command is run by first changing the flow of program from the current program to the dedicated executable.
-> This is done using fork() and execv(), while to run the further process smoothly by the parent process waitpid is used.
-> In the execuatbles the tokens are checked for specific signature of working commands, and no matching are run.
-> This cycles continues, till the users wishes.
-> To handle command with meaningful spaces, like name of a file, double qoutes should be used to enter such name. Example- "hello world.txt"
-> Check for file successfully opend
-> Check for process created successfully
-> Check for process ended successfully
-> Check for Insufficient arguments for command
-> Check for excess arguments for command
-> Check for unrecognized command
-> Check for Invalid command type
-> Check for File do not exits
-> Check for argument validity in context
-> cd - change the current working directory of shell
-> pwd - get the current working directory of shell
-> history - to check the entered commands
-> echo - to show user input back
-> exit - to exit the shell
-> cat - to print files
-> ls - to show content of current directory
-> date - to show the current time
-> rm - to remove a file
-> mkdir - to make directory
-> fork() - to create a child process
-> waitpid() - to wait parent for child process to finish
-> execv() - to call executable
-> exit() - to exit from a program
-> chdir() - to change the current working directory
-> getcwd() - to get the current working directory
-> getlogin() - to get the user logged in currently
-> scandir() - to scan the contents of a directory
-> fopen() - to open a file for reading/wrirting
-> fclose() - to close a file
-> fseek() - to reach a particular point in a file
-> fgets() - to read a line from a stream
-> fputs() - to transfer content to a stream'
-> time() - to get time in epoch form
-> strftime() - to format the time form
-> gmtime() - to get utc time
-> localtime() - to get local time
-> Using mkdir, changes access permission in the applied folder.