execute scripts when your machine is connected to a specific network

nm-scripts.sh

#!/usr/bin/env sh
#
# This script depends on ``nmcli`` (and network-manager).
#
# Use this script in a crontab to periodically execute scripts
# when your machine is connected to given networks.
#
# Scripts are stored in: ``~/.nm-scripts/${type}/${connection}``
#
# Sample crontab:
#
# ```
# SHELL=/bin/sh
# PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
#
# */2 * * * * root nm-scripts john-doe > /dev/null 2>&1 || :
# ```

export LANGUAGE=en_US
export LANG=en_US.UTF-8

main() {
    set_user "$1" || {
        echo 'argv[1] (user) required' 1>&2
        return 22 # EINVAL
    }

    is_logged_user || {
        echo "user (${NM_USER}) must be logged in" 1>&2
        return 130 # EOWNERDEAD
    }

    which nmcli > /dev/null || {
        echo 'nmcli required' 1>&2
        return 95 # EOPNOTSUPP
    }

    set_status
    test "$(echo "${NM_STATUS}" | wc -l)" -gt 0 || {
        return 100 # ENETDOWN
    }

    echo "Connected (${NM_USER}):\n${NM_STATUS}\n" | sed 's#/#\t#g'

    execute_network_scripts
}

# Define ``NM_USER``
#
# User manipulating nm-cli (through sudo or crontab user)
set_user() {
    local user=${1}

    test -z "$1" && {
        user=${SUDO_USER}
    }

    test -n "${user}" && {
        export NM_USER=${user}
    } || {
        return 1
    }
}

is_logged_user() {
    test $(w -hs "${NM_USER}" | wc -l) -gt 0
}

set_status() {
    export NM_STATUS="$(sudo -u "${NM_USER}" \
                             nmcli -t --fields state,type,connection d | \
                                         grep -E '^connected' | \
                                         grep -Ev -- ':--$' | \
                                         awk -F ':' '{print $2"/"$3}')"
}

# Scripts MUST be accessible through ``~/.nm-scripts``
#
# scripts are executed as ``root``
# scripts receive the following arguments:
# * ``$1`` ``NM_USER``
# * ``$2`` ``NM_STATUS``
execute_network_scripts() {
    local nm_dir=$(getent passwd "${NM_USER}" | cut -d: -f6)/.nm-scripts

    echo "$NM_STATUS" | while read line; do
        script="${nm_dir}/${line}"

        test -f "${script}" || continue
        test -x "${script}" || continue

        echo "Executing... ${line}"
        "${script}" "${NM_USER}" "${NM_STATUS}" || {
            echo "Script '${line}', terminated with status ${?}" 1>&2
        }
    done
}

main "$@"