how to create a sawtooth .wav sound file with sox

how to create a .5 second long sawtooth sound with a frequency of 100 cps, and write it to a file named saw.wav:

+* rec saw.wav synth 0.5 sawtooth 100 *+

n=saw.wav   # file name
l=0.5       # length in seconds
f=100       # frequency

rec $n synth $l sawtooth $f