How to check if docker pull actually pulled something

Question

I've the following script to update my Nextcloud:

#!/bin/bash

set -ex

docker pull nextcloud
docker rm -f nextcloud
docker run -d -p 8080:80 -v nextcloud:/var/www/html --name nextcloud --restart=unless-stopped nextcloud
docker image prune -f

The problem is, that it creates new container even when there was noting new to pull.

How can I check, if the docker pull actually pulled something, or if my image is already up-to-date? The exit code of docker pull is 0 in both situations.

Answer 1

You can check output of docker pull command:

#!/bin/bash    
set -ex

out=$(docker pull nextcloud)

if [[ $out != *"up to date"* ]]; then
   docker stop nextcloud
   docker rm -f nextcloud
   docker run -d -p 8080:80 -v nextcloud:/var/www/html --name nextcloud -- 
   restart=unless-stopped nextcloud
   docker image prune -f
fi