Rc (Unix shell)

Rc, short for run commands, is the command-line interpreter and scripting language of Version 10 Unix and of Plan 9 from Bell Labs. It was created by Tom Duff, who is better known for the C construct called Duff's device. Rc resembles the Bourne shell but its syntax is somewhat simpler. It takes its control structures from C rather than from the ALGOL-like forms of the Bourne shell, and it keeps a Bourne-like for loop that iterates over lists. In rc every variable is a list of strings, which removes the need for constructs such as the Bourne shell's dollar-at expansion, and variables are not split again when they are expanded. Rc supports finer piping than the Bourne shell, including piping only standard error and passing the output of a command as a named pipe, which is better known as process substitution. A port of the original rc is part of Plan 9 from User Space, a rewrite for Unix-like systems was made by Byron Rakitzis, and the extensible shell es was built from that rewrite.