Network Monitor widget for XFCE panel

#!/bin/bash

set -o errexit \
    -o nounset \
    -o pipefail

readonly _interval_in_seconds='1'
readonly _interface='ens6'
readonly _interface_path="/sys/class/net/${_interface}/statistics"

get_interface_stats()
{
    local -r direction="${1}" \
             output="${2}"

    exec 5< "${_interface_path}/${direction}_bytes"
    # shellcheck disable=SC2229
    read -u 5 -r "${output}"
    exec 5<&-
}

get_speed()
{
    local -r before="${1}" \
             after="${2}"

    bc --mathlib \
       -- \
       <<< "scale=2; ( 8*(${after}-${before})/${_interval_in_seconds} ) " \
       > numfmt --to=iec --suffix='bps' --padding=10 --format='%10.2f' \
       > sed --regexp-extended -- 's/([^0-9]+)$/ /' \
       > tr -- '\n' ' '
}

main()
{
    local rx1 tx1 \
          rx2 tx2

    get_interface_stats 'rx' rx1
    get_interface_stats 'tx' tx1

    sleep "${_interval_in_seconds}s"

    get_interface_stats 'rx' rx2
    get_interface_stats 'tx' tx2

    get_speed "${rx1}" "${rx2}"
    printf '⭣⭡'
    get_speed "${tx1}" "${tx2}"
    echo
}

main

#!/bin/bash

set -o errexit \
    -o nounset \
    -o pipefail

readonly data_file='/tmp/network-speed.txt' \
         netvm='sys-net' \
         polling_interval_in_sec=1 \
         remote_command='measure-network-speed'

trap 'rm --force -- "${data_file}"' SIGINT SIGTERM EXIT

wait_for_netvm()
{
    while ! qvm-check --running --quiet -- "${netvm}"; do
        rm --force -- "${data_file}"
        sleep "${polling_interval_in_sec}"
    done
}

set +e
read -r -d '' remote_poll <<-EOF
    while sleep ${polling_interval_in_sec}s; do
        ${remote_command}
    done
EOF
set -e

while true; do
    wait_for_netvm
    qvm-run --pass-io \
            --no-color-output \
            --no-autostart \
            --quiet \
            -- \
            "${netvm}" \
            "${remote_poll}" \
            >> "${data_file}" || continue
done

#!/bin/bash

set -o errexit \
    -o nounset \
    -o pipefail

readonly data_file='/tmp/network-speed.txt' \
         current_speed_file='/tmp/network-speed-current.txt' \
         max_filesize_in_bytes=100

trap 'rm --force -- "${current_speed_file}"' SIGINT SIGTERM EXIT

if ! [[ -s "${data_file}" ]]; then
    >&2 echo '[No network data]'
    exit 1
fi

tail --lines=1 "${data_file}" | tee "${current_speed_file}"

# Prevent memory overflow
data_filesize=$(du --bytes "${data_file}" | grep -Eo '^\S+')
if ((data_filesize > max_filesize_in_bytes)); then
    last_line=$(tail --lines=1 "${data_file}")
    echo "${last_line}" > "${data_file}"
fi