Shell and System Calls

Must be written in C Full project is attached.... What I need done however is below: -You may assume that there are no duplicate pathnames present, being added, or being deleted. You will restore your PATH environment variable to its original state (i.e., before your shell was invoked) when the user exits your [login to view URL] a new built-in myhistory command that lists the shell history of previous commands run in your shell (not the bash shell). Note that this does not have to work with the up-arrow key as in bash, but only with a new myhistory command run inside your shell. You may not make use of the history built-in command, but instead keep track of your history of commands in some sort of data structure. Your myhistory built-in command should support a history of 20 most recent commands (i.e., this means that the 21st command will overwrite the 1st command, for example). Your myhistory command should support a couple flags: -c to clear your myhistory list by deleting all entries, and -e <myhistory_number> to execute one of your twenty myhistory commands in your list. - Implement a new alias command (mandatory for teams of 4 and not required for teams of 3) Add a new built-in alias command that allows you to define a shortcut for commands by essentially defining a new command that substitutes a given string for some command, perhaps with various flags/options. The syntax is as follows: alias alias_name='command'. For example, you can define an alias with alias ll='ls –al', so that the user can then enter ll at the prompt to execute the ls -al command. Although there is an alias command in bash, you must implement your own version and not make use of the built-in alias bash command. Typically, alias is a built-in command, but since this affects how your shell functions (i.e., you simply cannot just pass an aliased command to the exec family system call as you are managing the execution which would otherwise result in a not found message.