Ensure input volume is always above a certain level

fix-input-volume.sh

#!/bin/bash
# fix-input-volume.sh - Ensure input volume is always above a certain level
# Copyright (C) 2022  Rene Luria <rene@luria.ch>
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.

MINIMUM_VOLUME=15
INTERVAL=1

usage() {
    cat <<EOD
fix-volume.sh

Ensure input volume is always above a certain level

Usage: fix-volume.sh [-m <vol>] [-i <seconds>]
    -m <vol>     : sets minimum volume to <vol> (default: $MINIMUM_VOLUME)
    -i <seconds> : seconds between each check (default: $INTERVAL)
EOD
}

get_volume() {
    osascript -e "input volume of (get volume settings)"
}

set_volume() {
    local volume="$1"
    osascript -e "set volume input volume $volume"
}

min_volume=$MINIMUM_VOLUME
interval=$INTERVAL

while getopts "hm:i:" OPTION; do
    case "$OPTION" in
        h)
            usage
            exit 0
            ;;
        m)
            min_volume="$OPTARG"
            ;;
        i)
            interval="$OPTARG"
            ;;
        *)
            echo "Error: bad arguments" >&2
            exit 1
            ;;
    esac
done
shift $((OPTIND - 1))

if [[ $# -ne 0 ]]; then
    echo "Error: too many arguments" >&2
    exit 1
fi

# check minimum volume argument
if ! [[ $min_volume =~ ^[0-9]{1,3}$ ]]; then
    echo "Error: bad volume format" >&2
    exit 1
fi
if [[ $min_volume -gt 100 ]]; then
    echo "Error: volume must be between 0 and 100" >&2
    exit 1
fi

# check interval argument
if ! [[ $interval =~ ^[0-9]+$ ]]; then
    echo "Error: bad interval format" >&2
    exit 1
fi

while sleep "$interval"; do
    volume=$(get_volume)
    if [[ $volume -lt $min_volume ]]; then
        echo "Input volume at $volume%, resetting to $min_volume"
        set_volume "$min_volume"
    fi
done