My goal is to be able to mute the Spotify application, not the entire system. Using the command: ps -C spotify -o pid= I am able to find the process ID of Spotify, in this case the ID is "22981". With that process ID I would like to search from this list: pacmd list-sink-inputs. That command returns a list like this:

eric@eric-desktop:~$ pacmd list-sink-inputs

Welcome to PulseAudio! Use "help" for usage information.

>>> 1 sink input(s) available.

    index: 0

    driver: <protocol-native.c>

    flags: START_CORKED 

    state: RUNNING

    sink: 1 <alsa_output.pci-0000_00_1b.0.analog-stereo>

    volume: 0: 100% 1: 100%

            0: -0.00 dB 1: -0.00 dB

            balance 0.00

    muted: no

    current latency: 1019.80 ms

    requested latency: 371.52 ms

    sample spec: s16le 2ch 44100Hz

    channel map: front-left,front-right

                 Stereo

    resample method: (null)

    module: 8

    client: 10 <Spotify>

    properties:

        media.role = "music"

        media.name = "Spotify"

        application.name = "Spotify"

        native-protocol.peer = "UNIX socket client"

        native-protocol.version = "26"

        application.process.id = "22981"

        application.process.user = "eric"

        application.process.host = "eric-desktop"

        application.process.binary = "spotify"

        window.x11.display = ":0"

        application.language = "en_US.UTF-8"

        application.process.machine_id = "058c89ad77c15e1ce0dd5a7800000012"

        application.process.session_id = "058c89ad77c15e1ce0dd5a7800000012-1345692739.486413-85297109"

        application.icon_name = "spotify-linux-512x512"

        module-stream-restore.id = "sink-input-by-media-role:music"

Now I would like to correlate the application.process.id = "22981" to the sink input index which in this case is index: 0. Now with that index number I would then need to to run this command: pacmd set-sink-input-mute 0 1 to mute Spotify and pacmd set-sink-input-mute 0 0 to unmute Spotify. For those commands, the first number would need to be replaced with the index number found earlier, and the next number is the boolean to turn on or off the mute. How can I put this altogether into a script, so I can get a command to mute/unmute the Spotify application?

EDIT:
Both of the scripts below work as expected, can somebody add a toggle which would check muted: yes or muted: no and then mute or unmute accordingly?

EDIT:
I was able to modify glenn jackman's script to add the toggle:

#!/bin/bash



main() {

    local action=toggle

    while getopts :mu option; do 

        case "$option" in 

            m) action=mute ;;

            u) action=unmute ;;

            ?) usage 1 "invalid option: -$OPTARG" ;;

        esac

    done

    shift $((OPTIND - 1))

    local pid=$(pidof "$1")

    if [[ -z "$pid" ]]; then

        echo "error: no running processes for: $1" >&2

    elif [[ "$1" ]]; then

        $action "$1"

    else

        usage 1 "specify an application name" 

    fi

}



usage() {

    [[ "$2" ]] && echo "error: $2"

    echo "Usage: $0 [-m | -u] appname"

    echo "Default: toggle mute"

    echo "Arguments:"

    echo "-m = mute application"

    echo "-u = unmute application"

    exit $1

}



toggle() {

    local status=$(get_status "$1")

    if [[ "$status" == "yes" ]]; then

      unmute "$1"

    elif [[ "$status" == "no" ]]; then

      mute "$1"

    fi

}



mute()   { adjust_muteness "$1" 1; }

unmute() { adjust_muteness "$1" 0; }



adjust_muteness() { 

    local index=$(get_index "$1")

    local status=$(get_status "$1")

    [[ "$index" ]] && pacmd set-sink-input-mute "$index" $2 >/dev/null 

}



get_index() {

    local pid=$(pidof "$1")

    pacmd list-sink-inputs | 

    awk -v pid=$pid '

    $1 == "index:" {idx = $2} 

    $1 == "application.process.id" && $3 == """ pid """ {print idx; exit}

    '

}



get_status() {

   local pid=$(pidof "$1")

   pacmd list-sink-inputs | 

   awk -v pid=$pid '

   $1 == "muted:" {idx = $2} 

   $1 == "application.process.id" && $3 == """ pid """ {print idx; exit}

   '

}



main "$@"