Replacing IP in curl command with bash variable - bash

Question

I'm currently trying to make a DDNS script that interacts with the Cloudflare API to catch changes in my ip address and automatically fix the ip address change for my web server. Everything is working correctly so far except I can't get $IP to be put properly in the curl statement. I first run a python script from within the bash script to get the ip address, then run the curl statement in the bash script. Here's what the python script looks like (it returns an ip address like "1.1.1.1" with quotations included because the curl command requires the quotations)
#!/usr/bin/python3
import subprocess as sp
def main():
command = "dig +short myip.opendns.com #resolver1.opendns.com";
ip = sp.check_output(command, shell=True).decode('utf-8').strip('\n');
ip_tmp = ip;
ip_tmp = '"' + ip + '"';
ip = ip_tmp;
print(ip);
if __name__ == "__main__":
main();
And the bash script looks like this:
#!/bin/bash
IP=$("./getIP.py")
curl -X PUT "https://api.cloudflare.com/client/v4/zones/zone_id/dns_records/dns_id" \
-H "X-Auth-Email: example.com" \
-H "X-Auth-Key: authkey" \
-H "Content-Type: application/json" \
--data '{"type":"A","name":"example.com","content":$IP,"ttl":120,"proxied":true}'
I've tried to have the python script only return numbers and then added the quotations in the bash script and now vice versa and I can't seem to get it to work. The last line should end up looking like this once the variable replaces with quotations around the ip address:
'{"type":"A","name":"example.com","content":"127.0.0.1","ttl":120,"proxied":true}'

Answer 1

The single quotes around your json structure prevent the variable from expanding.
You have a few options that are readily available.
Ugly quote escaping inside/around your json.
"{\"type\":\"A\",\"name\":\"example.com\",\"content\":$IP,\"ttl\":120,\"proxied\":true}"
Having the python write this data to a file and telling curl to use that file for the source of the post data.
curl -X PUT "https://api.cloudflare.com/client/v4/zones/zone_id/dns_records/dns_id" \
-H "X-Auth-Email: example.com" \
-H "X-Auth-Key: authkey" \
-H "Content-Type: application/json" \
--data #file_you_wrote_your_json_to.json
Using the python requests or urllib modules to issue the request to cloud flare.
Update your main() function to return the IP instead of print it.
my_ip = main()
url = "https://api.cloudflare.com/client/v4/zones/zone_id/dns_records/dns_id"
myheaders = {
"X-Auth-Email": "example.com",
"X-Auth-Key": "authkey",
"Content-Type": "application/json"
}
myjson = {
"type":"A",
"name":"example.com",
"content":my_ip,
"ttl":120,
"proxied":true
}
requests.put(url, headers=myheaders, data=myjson)

Answer 2

Better yet, just do it in bash. Cloudflare DDNS on github.
One shot to fetch the dynamic A-record ID:
curl -X GET "https://api.cloudflare.com/client/v4/zones/**Zone ID** \
/dns_records?type=A&name=dynamic" \
-H "Host: api.cloudflare.com" \
-H "User-Agent: ddclient/3.9.0" \
-H "Connection: close" \
-H "X-Auth-Email: example#example.com" \
-H "X-Auth-Key: "**Authorization key**" \
-H "Content-Type: application/json"
Cron job (* * * * *) to set the dynamic A-record:
#/usr/bin/env sh
AUTH_EMAIL=example#example.com
AUTH_KEY=** CF Authorization key **
ZONE_ID=** CF Zone ID **
A_RECORD_NAME="dynamic"
A_RECORD_ID=** CF A-record ID from cloudflare-dns-id.sh **
IP_RECORD="/tmp/ip-record"
RECORDED_IP=`cat $IP_RECORD`
PUBLIC_IP=$(curl --silent https://api.ipify.org) || exit 1
if [ "$PUBLIC_IP" = "$RECORDED_IP" ]; then
exit 0
fi
echo $PUBLIC_IP > $IP_RECORD
RECORD=$(cat <<EOF
{ "type": "A",
"name": "$A_RECORD_NAME",
"content": "$PUBLIC_IP",
"ttl": 180,
"proxied": false }
EOF
)
curl "https://api.cloudflare.com/client/v4/zones/$ZONE_ID \
/dns_records/$A_RECORD_ID" \
-X PUT \
-H "Content-Type: application/json" \
-H "X-Auth-Email: $AUTH_EMAIL" \
-H "X-Auth-Key: $AUTH_KEY" \
-d "$RECORD"