Here's a recursive Python program that finds the greatest common denominator:
#!/usr/bin/python
import sys
def gcdR( x, y ):
if( y ):
return( gcdR( y, x % y ) )
return x
if( __name__ == "__main__" ):
x = max( int( sys.argv[ 1 ] ), int( sys.argv[ 2 ] ) )
y = min( int( sys.argv[ 1 ] ), int( sys.argv[ 2 ] ) )
print gcdR( y, x % y )
sys.exit( 0 )
