Cloudflare API v4 Dynamic DNS updater for BSD Bash

cf-ddns.sh

#!/bin/sh
#
# 10/16/2016
# Cloudflare api script written in bash
#
# Using crontab, you should schedule this to run daily
# Something like: 0 */12 * * * (for noon and midnight)

# CHANGE THESE
cf_email="user@example.com"
auth_key="c2547eb745079dac9320b638f5e225cf483cc5cfdda41" # found in cloudflare account settings
zone_name="example.com"
record_name="www.example.com"

# MAYBE CHANGE THESE
IP=$(curl -s http://ipv4.icanhazip.com)
#IP=`wget -O - -q http://icanhazip.com`
IP_file=".old-ip-cf.txt"
id_file="cloudflare.ids"
log_file="cloudflare.log"

# LOGGER
log() {
    if [ "$1" ]; then
        echo -e "[$(date)] - $1" >> $log_file
    fi
}
# contains(string, substring)
#
# Returns 0 if the specified string contains the specified substring,
# otherwise returns 1.
contains() {
    string="$1"
    substring="$2"
    if test "${string#*$substring}" != "$string"
    then
        return 0    # $substring is in $string
    else
        return 1    # $substring is not in $string
    fi
}

# SCRIPT START
log "DDNS Check Initiated..."

if [ -f $IP_file ]; then
    OLD_IP=$(cat $IP_file)
    if [ $IP == $OLD_IP ]; then
        log "IP Unchanged."
        exit 0
    fi
else
    log "No old IP on file, fetching..."
fi

if [ -f $id_file ] && [ $(wc -l $id_file | cut -d " " -f 1) == 2 ]; then
    zone_identifier=$(head -1 $id_file)
    record_identifier=$(tail -1 $id_file)
    log "IDs were read from file..."
else
    zone_identifier=$(curl -s -X GET "https://api.cloudflare.com/client/v4/zones?name=$zone_name" -H "X-Auth-Email: $cf_email" -H "X-Auth-Key: $cf_key" -H "Content-Type: application/json")

    regex='"id"\:"([0-9a-z]*)"*'
    if [[ $zone_identifier =~ $regex ]]; then
        zone_identifier="${BASH_REMATCH[1]}"
    fi
    echo "$zone_identifier" > $id_file

    record_identifier=$(curl -s -X GET "https://api.cloudflare.com/client/v4/zones/$zone_identifier/dns_records?name=$record_name" -H "X-Auth-Email: $cf_email" -H "X-Auth-Key: $cf_key" -H "Content-Type: application/json")

    if [[ $record_identifier =~ $regex ]]; then
        record_identifier="${BASH_REMATCH[1]}"
    fi
    echo "$record_identifier" >> $id_file
    log "IDs fetched from cf."
fi

update=$(curl -s -X PUT "https://api.cloudflare.com/client/v4/zones/$zone_identifier/dns_records/$record_identifier" -H "X-Auth-Email: $cf_email" -H "X-Auth-Key: $cf_key" -H "Content-Type: application/json" --data "{\"id\":\"$zone_identifier\",\"type\":\"A\",\"name\":\"$record_name\",\"content\":\"$IP\"}")

if (contains "$update" '"success":false')
then
    msg="API UPDATE FAILED. DUMPING RESULTS:\n$update"
    log "$msg"
    echo -e "$msg"
    exit 1
else
    log "Writing IP to file..."
    echo "$IP" > $IP_file
    log "IP changed to: $IP"
    echo "$msg"
fi