btw/btw

#!/bin/sh
#
# * Battery Watchdog (see help text below).
#
# This is free and unencumbered software released into the public domain.
#
# Anyone is free to copy, modify, publish, use, compile, sell, or
# distribute this software, either in source code form or as a compiled
# binary, for any purpose, commercial or non-commercial, and by any
# means.
#
# In jurisdictions that recognize copyright laws, the author or authors
# of this software dedicate any and all copyright interest in the
# software to the public domain. We make this dedication for the benefit
# of the public at large and to the detriment of our heirs and
# successors. We intend this dedication to be an overt act of
# relinquishment in perpetuity of all present and future rights to this
# software under copyright law.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
# IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
# OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
# ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
# OTHER DEALINGS IN THE SOFTWARE.
#
# For more information, please refer to <http://unlicense.org/>
#                               ---
# Dependencies:
#   acpi            <https://sourceforge.net/projects/acpiclient/>
#   libnotify       <https://salsa.debian.org/gnome-team/libnotify>
#
# Installation:
#   # on Arch Linux:
#   pacman -S acpi        # (commynity repo)
#   pacman -S libnotyfy   # (extra repo)
#   # on Debian/Ubuntu:
#   apt-get install acpi
#   apt-get install libnotify

print_help() {
    printf \
"btw - battery watchdog. Send notification when critical battery level reached.

Usage:
    btw [-c|--crit \033[4mvalue\033[0m] [-p|--preriod \033[4mseconds\033[0m] \
[-l|--log \033[4mfile\033[0m]
        [-j|--syslog] [-s|--summary t\033[4mext\033[0m] \
[-b|--body t\033[4mext\033[0m] [-w|--watch]
    btw --help
    btw --version

Options:
    -v, --version
          Print version and exit.

    -h, --help
          Print this help message and exit.

    -c, --crit \033[4mvalue\033[0m
          Battery critical value in percents [default: 10]

    -p, --preriod \033[4mseconds\033[0m
          Battery check out period in seconds [default: 30]

    -l, --log \033[4mfile\033[0m
          Log file [default: ~/.cache/btw.log]

    -j, --syslog
          Use logger instead of log file.

    -s, --summary \033[4mtext\033[0m
          Custom notification title text.

    -b, --body \033[4mtext\033[0m
          Custom notification body text.

    -w, --watch
          Follow to the log file (tail -f).

See \033[1mbtw\033[0m(1) for full help.
"
}

send_notify() {
    notify-send --urgency=critical --icon=battery-empty --category=System \
        "$(eval echo "$1")" "$(eval echo "$2")"
}

is_int() {
    if [ -n "$1" ] && [ "$1" -eq "$1" ] 2>/dev/null; then
        return 0
    else
        echo 'Value is not integer' >&2; exit 1
    fi
}

# Transform long options to short ones
for ARG in "$@"; do
    shift
    case "$ARG" in
        --crit)
            set -- "$@" "-c"
            ;;
        --period)
            set -- "$@" "-p"
            ;;
        --log)
            set -- "$@" "-l"
            ;;
        --syslog)
            set -- "$@" "-j"
            ;;
        --summary)
            set -- "$@" "-s"
            ;;
        --body)
            set -- "$@" "-b"
            ;;
        --watch)
            set -- "$@" "-w"
            ;;
        --help)
            set -- "$@" "-h"
            ;;
        --version)
            set -- "$@" "-v"
            ;;
        *)
            set -- "$@" "$ARG"
    esac
done

# Parse short opts
while getopts c:p:l:js:b:whv OPT; do
    case "$OPT" in
        c)
            is_int "$OPTARG"
            critical="$OPTARG"
            ;;
        p)
            is_int "$OPTARG"
            period="$OPTARG"
            ;;
        l)
            log="$OPTARG"
            ;;
        j)
            syslog=1
            ;;
        s)
            summary="$OPTARG"
            ;;
        b)
            body="$OPTARG"
            ;;
        w)
            watch=1
            ;;
        h)
            print_help
            exit 0
            ;;
        v)
            echo 1.0
            exit 0
            ;;
        *)
            echo Unknown option: "$OPT" >&2
            exit 1
    esac
done

# Default values
period="${period:-30}"      # check battery every `period` seconds
critical="${critical:-10}"  # battery limit (in %)
clevel="${clevel:-100}"     # current battery value (in %, temporary variable)
summary="${summary:-Extremely low battery: \$level%}"
body="${body:-Check the charger, battery currently is \$state}"
lock=/tmp/btw.lock          # lock file
log="${log:-"$HOME"/.cache/btw.log}"

mkdir -p "$HOME"/.cache

if [ -n "$watch" ]; then
    if [ -n "$syslog" ]; then
        journalctl -t btw -f
    else
        tail -f "$log"
    fi
    exit "$?"
fi

printf 'crit: %s%%; period: %ss; log: %s\n' "$critical" "$period" "$log" >&2

while true; do
    battery="$(acpi -b | awk '{print $3 " " $4}' |
        sed -E 's/,|%//g;' | tr '[:upper:]' '[:lower:]')"
    level="${battery##* }"  # e.g. "49" (in percents)
    state="${battery%% *}"  # e.g. "charging"

    if [ "$level" -le "$critical" ]; then
        if [ ! -f "$lock" ]; then
            send_notify "$summary" "$body"
            touch "$lock"
        fi
        # Warn in every percent less
        if [ "$level" -le "$clevel" ]; then
            send_notify "$summary" "$body"
            touch "$lock"
            clevel="$level"
        fi
    else
        [ -f "$lock" ] && rm "$lock"
    fi

    log_message="$(printf '%s %s %s%%' \
        "$(date +'%Y-%m-%d %H:%M:%S')" "$state" "$level")"
    if [ -n "$syslog" ]; then
        echo "$log_message"
        logger -i "$$" -t btw -- "$log_message"
    else
        echo "$log_message" | tee -a "$log"
    fi

    sleep "$period"
done