OS X (Apple)

#!/bin/bash
# ac2dc.sh
# *********************************************************
# Generate a 1 second squarewave pulse and _voltage_double_ the output to DC.
# This is to be used as a set/reset pulse for the AudioScope.sh.
# Issued as Public Domain, CC0. You may do with it as you please.
# *********************************************************
if [ ! -e "/tmp/squarewave.wav" ]
then
	> /tmp/squarewave.wav
	printf "\x52\x49\x46\x46\x64\x1F\x00\x00\x57\x41\x56\x45\x66\x6D\x74\x20\x10\x00\x00\x00\x01\x00\x01\x00\x40\x1F\x00\x00\x40\x1F\x00\x00\x01\x00\x08\x00\x64\x61\x74\x61\x40\x1F\x00\x00" >> /tmp/squarewave.wav
	for n in {0..1999}
	do
		printf "\x00\x00\xFF\xFF" >> /tmp/squarewave.wav
	
	done
fi
# *********************************************************
# The line below uses various Linux flavours, "aplay"...
# aplay /tmp/squarewave.wav
# *********************************************************
# Use the OSX default basic command line audio player, "/usr/bin/afplay".
afplay /tmp/squarewave.wav
# *********************************************************
exit 0
# *********************************************************
# A very simple voltage doubler and passive filter for a control output.
# This will be used to set and reset a microphone input Analogue to Digital Converter, (ADC).
# Two ARE available and MIGHT be needed, but only ONE for definite.
# (Connect DC OUT & GND to a DC coupled oscilloscope to see it working.)
#
# Headset O/P. C1              |\|D2 
#  O--------o--||--o-------o---| +---o-------o-------O +VE DC OUT.
#           |      |       |   |/| + |       |
#  O        \      | +     \         |       \
#  |        /    --+--     /         | +     /
#  |   * R1 \     / \ D1   \ R2     === C2   \ R3
#  |        /    '---'     /        -+-      /
#  |        \      |       \         |       \
#  |        /      |       /         |       /
#  |        |      |       |         |       |
#  +--------o------o-------o---------o---o---o-------O -VE.
#                                      __|__
#                                      /////
# Parts List:-
# C1 ......... 1.0 uF, 50V.
# C2 ......... 10 uF, electrolytic, 10V.
# R1 ......... 47 KilOhms, (* this can be ommitted), 1/8W, 5% tolerence resistor.
# R2 ......... 1 MegOhm, 1/8W, 5% tolerence resistor.
# R3 ......... 100 KilOhms, 1/8W, 5% tolerence resistor.
# D1, D2 ..... OA90 or any similar germanium diode.
# 3.2 mm stereo jack plug for headset socket.
# Coaxial connecting cable.
# Sundries as required, stripboard, etc, (similar to above).
# *********************************************************
# I'll bet no one thought that the shell would become the basis of a testgear suite...

printf "\x52\x49\x46\x46\x64\x1F\x00\x00\x57\x41\x56\x45\x66\x6D\x74\x20\x10\x00\x00\x00\x01\x00\x01\x00\x40\x1F\x00\x00\x40\x1F\x00\x00\x01\x00\x08\x00\x64\x61\x74\x61\x40\x1F\x00\x00" >> /tmp/squarewave.wav