Source code in the unix programming language

gcd() {
	# Calculate $1 % $2 until $2 becomes zero.
	until test 0 -eq "$2"; do
		# Parallel assignment: set -- 1 2
		set -- "$2" "`expr "$1" % "$2"`"
	done

	# Echo absolute value of $1.
	test 0 -gt "$1" && set -- "`expr 0 - "$1"`"
	echo "$1"
}

gcd -47376 87843
# => 987

gcd() { until test 0 -eq "$2";do set -- "$2" "$(($1 % $2))";done;if [ 0 -gt "$1" ];then echo "$((- $1))";else  echo "$1"; fi }

gcd -47376 87843
# => 987

gcd () { if [ "$2" -ne 0 ];then gcd "$2" "$(($1 % $2))";else echo "$1";fi }

gcd 100 75
# => 25

alias gcd eval \''set gcd_args=( \!*:q )	\\
	@ gcd_u=$gcd_args[2]			\\
	@ gcd_v=$gcd_args[3]			\\
	while ( $gcd_v != 0 )			\\
		@ gcd_t = $gcd_u % $gcd_v	\\
		@ gcd_u = $gcd_v		\\
		@ gcd_v = $gcd_t		\\
	end					\\
	if ( $gcd_u < 0 ) @ gcd_u = - $gcd_u	\\
	@ $gcd_args[1]=$gcd_u			\\
'\'

gcd result -47376 87843
echo $result
# => 987