Create dockcheck_function.sh

first commit

dockcheck_function.sh

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+### Requires the regctl binary, either in PATH or as an alias
+### Get it here: https://github.com/regclient/regclient/releases
+
+alias="/path/to/regctl"
+dockcheck () {
+  if [[ -z "$1" ]]; then 
+    echo "No container name given, here's the list of currently running containers:" 
+    docker ps --format '{{.Names}}'
+  else
+    RepoUrl=$(docker inspect $1 --format='{{.Config.Image}}')
+    LocalHash=$(docker image inspect $RepoUrl --format '{{.RepoDigests}}' | sed -e 's/.*sha256/sha256/' -e 's/\]$//')
+    RegHash=$(regctl image digest --list $RepoUrl)
+    if [[ "$LocalHash" != "$RegHash" ]] ; then printf "Updates available.\n" ; else printf "Already latest.\n" ; fi
+  fi
+}