The shell program should be a BASH script or CSH script,

2. (20 pts) Write a simple single thread CSC4420 shell, i.e., no concurrent commands, to support at least the following built-in commands: prompt can set to any string you input, in addition to the current history event number, i.e, \%h as in csh; url : list the course web site hour : list class times room : list classroom location desp : list the description of this course text : list the textbook ref : list the reference books prof : list the professor's name pol : professor's office location poh : professor's office hours pma : professor's email address ta : list the TA's name tol : TA's office location toh: TA's office hours tma : TA's email address history : list history of events up to the number you set help : list all the available commands exit or quit : exit CSC4420 shell