bash script to change volume in ubuntu

vol

#!/bin/bash

# DO THIS FIRST:
# sudo aptitude install libnotify-bin alsa-utils

# INSTALL:
# mkdir ~/bin
# cp ~/Downloads/vol ~/bin/vol
# chmod +x ~/bin/vol

# USAGE:
# vol up
# vol down
# vol mute
# vol unmute
# vol 10+
# vol 5-
# vol 60%

# I usually use this from a launcher which can run arbitrary scripts, such
# as synapse or the alt+f2 launcher in 'buntu.

if [ $1 = "mute" ]
then
    amixer set Master mute
    notify-send "Volume muted"
elif [ $1 = "unmute" ]
then
    amixer set Master unmute
    notify-send "Volume unmuted"
elif [ $1 = "up" ]
then
    str=`amixer set Master 5+`
    vol=`echo $str| awk '{print $22}'`
    notify-send "Volume $vol"
elif [ $1 = "down" ]
then
    str=`amixer set Master 5-`
    vol=`echo $str| awk '{print $22}'`
    notify-send "Volume $vol"
else
    str=`amixer set Master $1`
    vol=`echo $str| awk '{print $22}'`
    notify-send "Volume $vol"
fi