update-record

#!/bin/sh
exec 3>&1

# get int value for given log level debug=>10, info=>20, error=>40
get_log_level_value(){
    level=20
    case $1 in
        debug)
        level=10
    ;;
        info)
        level=20
    ;;
        error)
        level=40
    ;;
    esac
    echo $level
}

# functions used to display logs
log(){
    log_level_value=$(get_log_level_value $1)
    if [ $log_level_value -ge $current_level_value ]
    then
    echo "{\"date\": \"$(date -u +"%Y-%m-%dT%H:%M:%SZ")\", \"level\": \"$1\", $levelvalue \"message\": \"$2\"}" 1>&3
    fi
}
debug(){ log debug "$1"; }
info(){ log info "$1"; }
error(){ log error "$1"; }

# validate inputs and set defaults

[ -z $HOSTNAME ] && echo You need to set environment variable HOSTNAME && exit
[ -z $IDENTIFIER ] && echo You need to set environment variable IDENTIFIER && exit
[ -z $PASSWORD ] && echo You need to set environment variable PASSWORD && exit
[ -z $LOG_LEVEL ] && LOG_LEVEL=debug

# set current log level, all logs with a lower level are filtered
current_level_value=$(get_log_level_value $LOG_LEVEL)

# retrieve last known (cached) address and current public address
CACHED_IP_ADDRESS=$(cat /dynhost/.cache/ip_address 2>/dev/null)
PUBLIC_IP_ADDRESS=$(dig @resolver4.opendns.com myip.opendns.com +short)

# compare current address to cached one to avoid useless updates
if [ "$CACHED_IP_ADDRESS" != "$PUBLIC_IP_ADDRESS" ]
then
    info "Cached address changed from '$CACHED_IP_ADDRESS' to '$PUBLIC_IP_ADDRESS'"
    # update DynHost record using OVH API
    ovh_response=$(curl -sS "http://www.ovh.com/nic/update?system=dyndns&hostname=${HOSTNAME}&myip=${PUBLIC_IP_ADDRESS}" \
        -H "Authorization: Basic $(echo -n $IDENTIFIER:$PASSWORD | base64)")
    debug "OVH response: ${ovh_response}"
    # cache address for comparison, to avoid useless updates
    mkdir -p .cache/
    echo $PUBLIC_IP_ADDRESS > /dynhost/.cache/ip_address
else
    debug "No changes detected"
fi