A Unix shell is a command language interpreter, the primary purpose of which is to translate command lines typed at a terminal into system actions. The shell itself is a program through which other programs are invoked. Although there are several different Unix shells, among them the C shell (csh), the Bourne shell and the Korn shell, the one most frequently used on Blake within Berkeley UNIX is the C shell.
UNIX Standard input for a process can be drawn from the script file itself. This uses the special redirection symbol "<<". The name which follows the redirection symbol is a tag for the end of the input. That is, the contents of the script file will be read as standard input to the process until a input line matching the name following the redirection symbol.