Replace ip:port to another ip:port using sed

Question

I have nginx config file, where i have ip adress of my container. If i recreate container it will have the new ip, so i want to replace it.

I have .sh script:

#!/bin/bash
ip_new=$(sudo docker exec -ti pqf_ui_dev hostname -I) #to assign  container ip to this variable
sudo sed  "s~proxy_pass http[:]//[^ ][:]80*~proxy_pass http://$ip_new:80~"  -i /etc/nginx/sites- 
enabled/docker-pqf

so for example if my old ip:port was 172.17.0.1:80 and the new one is 172.17.0.2:80, my sed replace it like:

proxy_pass http://172.17.0.4 ^M:80

How i can change my script to replace ip without this ^M ?

Answer 1

Use:

ip_new=$(docker inspect -f '{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' pqf_ui_dev)

Instead of:

ip_new=$(sudo docker exec -ti pqf_ui_dev hostname -I)

And maybe you may like this sed:

sudo sed -E 's~(proxy_pass https?://)[^ :;]+(:?\\d*)~\\1'$ip_new'\\2~' -i /etc/nginx/sites- enabled/docker-pqf

It is not perfect, but way more universal and without repeating searchtext like proto, host, port.

Answer 2

If I were doing this I would run the nginx proxy in a container also and proxy_pass to the container name rather than a dynamic IP that will keep changing.

eg if using a compose file

version: '3.7'
services:
  proxy:
    image: nginx
    # Docker config required for nginx
  backend: 
    # Config for your backend service
    ports:
     - "80:80"

Then in your nginx conf file you can refer to the backend service as http://backend:80 and docker DNS will resolve the IP address for you complete with load balancing if you have multiple instances running.