script to run rclone bisync in the background as a cronjob or systemd timer, sending a notification to the user if something goes wrong

rclone-bisync.sh

#!/usr/bin/env bash
#
# This script runs rclone bisync between two paths and sends a notification to
# the user if something goes wrong with notify-send.
# It is intended to run frequently with a cronjob or systemd user timer.
#
# rclone-bisync path1 path2 [--resync] [--verbose] [--dry-run]
#

verbose=false
path1=""
path2=""

bisync_args=(
    --check-access \
    --compare size,modtime,checksum \
    --download-hash \
    --conflict-resolve path1 \
    --resilient \
    --recover \
    --max-lock 5m \
    --color NEVER
)

verlog() {
    if ! [[ "$verbose" = "true" ]]; then
        return
    fi
    echo -e "$*"
}

show_help() {
    echo "rclone-bisync path1 path2 [--resync] [--dry-run] [--verbose]"
    echo "  (--resync implies --verbose)"
}

rclone_bisync() {
    rclone bisync \
    "$path1" \
    "$path2" \
    "${bisync_args[@]}"
}

# Wonky ass function that captures stdout, stderr and the return code of provided command.
# From https://stackoverflow.com/a/59592881/3283382
#   catch STDOUT_VARIABLE STDERR_VARIABLE COMMAND [ARG1[ ARG2[ ...[ ARGN]]]]
catch() {
    {
        IFS=$'\n' read -r -d '' "${1}";
        IFS=$'\n' read -r -d '' "${2}";
        (IFS=$'\n' read -r -d '' _ERRNO_; return "${_ERRNO_}");
    } < <(
        (
            printf '\0%s\0%d\0' "$(
                (
                    (
                        (
                            { shift 2; "${@}"; echo "${?}" 1>&3-; } | tr -d '\0' 1>&4-
                        ) 4>&2- 2>&1- | tr -d '\0' 1>&4-
                    ) 3>&1- | exit "$(cat)"
                ) 4>&1-
            )" "${?}" 1>&2
        ) 2>&1
    )
}

run() {
    verlog "Running the following command:\n" "rclone bisync $path1 $path2 ${bisync_args[*]}"
    # Declare variables to use for catch
    declare bisync_out bisync_err
    catch bisync_out bisync_err rclone_bisync
    # Save return code
    bisync_errno="$?"

    verlog "rclone bisync exited with $bisync_errno"
    verlog "Output:\n" "$bisync_out" "$bisync_err"
    
    # Only send message if return code is greater than 0
    if (( bisync_errno > 0 )); then
        summary="rclone bisync exited with $bisync_errno!"
        message="Error: $bisync_err\nOutput: $bisync_out"
        notify-send --urgency=critical "$summary" "$message"
    fi
}

# At least two parameters must be provided.
provided_parameters="$#"
if (( provided_parameters < 2 )); then
    echo "path1 and path2 must be provided!"
    show_help
    exit
fi

# Read paths
path1="$1"
shift
path2="$1"
shift

# Parse optional options
while :; do
    case $1 in
        -h|-\?|--help)
            show_help
            exit
            ;;    
        --resync)
            bisync_args+=("--resync" "--verbose")
            verbose=true
            ;;
        --dry-run)
            bisync_args+=("--dry-run")
            ;;
        --verbose)
            bisync_args+=("--verbose")
            verbose=true
            ;;
        --)
            shift
            break
            ;;
        -?*)
            printf 'WARN: Unknown option %s\n' "$1" >&2
            exit 1
            ;;
        *)
            break
    esac

    shift
done

# Run!
run