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Name: 
    myshell
Synopsis:
    myshell [batch.txt]
Run:
    1. make
    2. ./myshell [batch.txt]
Description:
    Batch Mode:
        Shell reads file which contains multiple lines of commands, 
            and should be able to execute each command
    Internal commands:
            a. cd <directory> - Change the current default directory to <directory>. 
                If the <directory> argument is not present, report the current directory. 
                If the directory does not exist an appropriate error should be reported. 
                This command should also change the PWD environment variable.
            b. clr - Clear the screen.
            c. dir <directory> - List the contents of directory
                <directory>.
            d. environ - List all the environment strings.
            e. echo <comment> - Display <comment> on the display followed
                by a new line (multiple spaces/tabs may be reduced to a
                single space).
            f. help - Display the user manual using the more filter.
            g. pause - Pause operation of the shell until 'Enter' is
                pressed.
            h. quit - Quit the shell.
            i. The shell environment should contain
                shell=<pathname>/myshell where <pathname>/myshell is the
                full path for the shell executable(not a hardwired path
                back to your directory, but the one from which it was
                executed).
    I/O Redirections:
        myshell supports on either or both stdin and/or stdout. The command line
        
            programname arg1 arg2 < inputfile > outfile
        
        will execute the program programname with arguments arg1 and arg2, 
        the stdin FILE stream replaced by inputfile and the stdout FILE 
        stream replaced by outputfile.
        
        stdout redirection should also be possible for the internal commands 
        
            dir, environ, echo, & help.

        With output redirection, if the redirection character is > then the 
        outputfile is created if it does not exist and truncated if it does. 
        If the redirection token is >> then outputfile is created if it does 
        not exist and appended to if it does.
    Background programs:
        An ampersand (&) at the end of the command line indicates that the shell 
        should return to the command line prompt immediately after launching that 
        program.
    Pipes:
        Several commands are strung together
        command1 arg1 | command2 arg2
    Path Environment:
        Path environment contains path to find myshell