Rc

rc is a simple yet powerful shell written by Tom Duff. Originally used on AT&T's Version 10 UNIX, it is now primarily used under Plan 9, where it is the default shell. Despite rc's simplicity, it is powerful enough that many of Plan 9's basic utilities are written using it.

Examples

Here is a script to check the weather in a given city. (Retrieved from http://plan9.bell-labs.com/sources/plan9/rc/bin/weather)

#!/bin/rc
rfork e
DEFAULT=ewr
fn usage{
	echo 'usage: weather 3-letter-city-code' >[1=2]
	echo 'for a list of cities in new york, say' >[1=2]
	echo '	weather ny' >[1=2]
	exit usage
}
switch($#*){
case 0
	arg=$DEFAULT
	if(~ $#weather 1)
		arg=$weather
case 1
	arg=$1
case *
	usage
}
switch($arg){
case [a-zA-Z][a-zA-Z][a-zA-Z]
	script=(  'C' '4' '1' '1' $arg     'X')
case [a-zA-Z][a-zA-Z]
	script=(  'C' '4' '1' '3' $arg     'X')
case *
	usage
}
{
	for(i in $script)
		echo $i
} |
con -nrl tcp!rainmaker.wunderground.com!telnet |
sed -n '/Enter .-letter .* code:/,/CITY FORECAST MENU/p' |
sed 's/Enter .-letter .* code: //' |
sed 's/   Press Return to continue, M to return to menu, X to exit: //' |
grep -v 'CITY FORECAST MENU' |
tr -d '
' |
sed 's/ *$//' |
uniq