pedalVol.sh

#!/bin/bash
MAXVOL=40
MAXMICVOL=25
SINKAPP="mpd"

readfile=true
if [ "d$1" != "d" ] 
then
	MAXVOL=$1
	echo "$MAXVOL" > ~/.maxvol
fi

RIGHTPTOP=162311
RIGHTPBOT=114070

RIGHTPRANBOT=$(expr $RIGHTPBOT - 10)

RIGHTPDIF=$(expr $RIGHTPTOP - $RIGHTPBOT)
maxdiv="0.$(echo $MAXVOL)"
maxmicdiv="0.$(echo $MAXMICVOL)"
paused="0"
voladjust=$(expr 100 - $MAXVOL)
#--Gets input from the joystick device for one 1/100 of a second
#-The awk numbr varible selects the analog axis input
function getInput()
{
	input=$(timeout 0.05s cat /dev/input/js0 | od | awk '{print $8}')
}

#--Checks for input range and calls to set volume
function inputToVol
{
	getInput
	getMaxVol



	input=( $(echo $input | tr "\n" " ") )
	input="${input[6]}"
	if [ "$input" -lt $RIGHTPTOP ] && [ "$input" -gt $RIGHTPRANBOT  ]
	then
		input="$(expr $input - $RIGHTPBOT)00"
		percent="$(expr $input / $RIGHTPDIF)"
		int=$(bc <<< "$percent  * $maxdiv")
		int=${int%.*}
		if [ "$int" -lt 5 ]
		then
			setVol "0"
			if [ "$paused" == "0" ]
			then
				mpc pause
				paused="1"
				sleep 0.5 
			fi
		else
			setVol $int
			if [ "$paused" == "1" ]
			then
				mpc play
				paused="0"
			fi
		fi

	else
		setVol $MAXVOL
	fi

	if [ "$input" -gt 0 ] && [ "$input" -lt 37175  ]
	then
		input="$(expr 37174 - $input)00"
		percent="$(expr $input / 37174)"
		int=$(bc <<< "$percent  * $maxmicdiv")
		int=${int%.*}
		
		if [ "$int" -lt 5 ]
		then
			setMicVol 0
		else
			setMicVol ${int%.*}
		fi

	else

		setMicVol $MAXMICVOL
	fi
}

#--Sets volume from percent parameter
function setVol()
{
	 pactl set-sink-input-volume $sink $1% 
}

#--Sets volume from percent parameter
function getMaxVol()
{
	if [ $readfile ]
	then
		if [ -f ~/.maxvol ]
		then
			MAXVOL=$(cat ~/.maxvol)
			maxdiv="0.$(echo $MAXVOL)"
		else
			echo "No file"
			echo "$MAXVOL" > ~/.maxvol
		fi
	fi
}

#--Sets volume from percent parameter
function setMicVol()
{
	 pactl set-source-volume alsa_input.pci-0000_00_1b.0.analog-stereo $1% 
}

function getSink()
{
	sinks=$(pactl list sink-inputs)
	sinkbinaryindex=$(awk -v sinks="$sinks" -v app="$SINKAPP" 'BEGIN {print index(sinks,app)}'  )
	sink=$(echo "${sinks:0:$sinkbinaryindex}" | tr "\n" "[racecar]" | rev | tr "[racecar]" "\n" | grep -m 1 "tupnI" | tr -d "#" | awk '{print $1}' | rev )
	echo "$cutatapprev"
}

# rootTest
# Tests if the script was run qith root permissions and tells the user they need to if they didn't.
function rootTest ()
{
	if [[ $EUID -ne 0 ]] 
	then
   		echo "You need to run this as root to be able to make system changes"
		echo -e "Run \"sudo $0\" next time"
		exit 1
	fi
}

#---------------- Logic ----------------#
rootTest
getSink 

echo "Using sink: $sink"

#--Main Loop
while true
do
	inputToVol
done

Thank you for my inspiration by getSink() function. I learnt couple of new things :-) . Just a few notes:

• If the code tr "\n" "[racecar]" and tr "[racecar]" "\n" suppose to change end of line for something and then back, it does not work in this way (tr replaces single chars). I modified your code for myself in this way:
  sink=$(echo "${sinks:0:$sinkbinaryindex}" | awk 1 ORS='my_end_of_line' | rev | sed -r -e 's/enil_fo_dne_ym/\n/g' | grep -m 1 "tupnI" | cut -d'#' -f1 | rev )
• $cutatapprev was not set so it prints an empty line.