Hardware Reference
In-Depth Information
4.
After the first
#!/bin/sh
line, you're free to put anything in this script. Just
keep in mind that you won't be able to use aliases here—you'll have to enter
full commands.
Here's an example record and playback script:
#!/bin/sh
#
# Auto-run script for Raspberry Pi.
# Use chmod +x ~/autorun.sh to enable.
PLAYORREC=P # Set to P for Playback or R for Record
INPUTFILE="playme.wav"
OUTPUTFILE="myrec.wav"
MICROPHONE="-t alsa plughw:1"
SPEAKERS="-t alsa plughw:0"
case "$PLAYORREC" in
P|p) sox ~/"$INPUTFILE" $SPEAKERS ;;
R|r) sox $MICROPHONE ~/"$OUTPUTFILE" ;;
*) echo "Set the PLAYORREC variable to P for Playback or R for
Record" ;;
esac
° The first
#!/bin/sh
line is called a
shebang
and is used to tell the
system that any text that follows is to be passed on to the default
shell (which is
dash
during boot and
bash
for logins on Raspbian)
as a script.
° The other lines starting with
#
characters are comments, used only to
convey information to anyone reading the script.
° The
PLAYORREC
variable is used to switch between the two operating
modes of the script.
°
INPUTFILE
is what will be played if we are in the playback mode, and
OUTPUTFILE
is where we will record to if we are in the record mode.
°
MICROPHONE
and
SPEAKERS
lets us update the script easily for
different audio gadgets.
° The case block compares the character stored in the
PLAYORREC
variable (which is
P
at the moment) against three possible cases.
If
PLAYORREC
contains a capital
P
or a lowercase
p
), then run this
sox
playback command.
