The meaning of $() as per here is:
The syntax is token-level, so the meaning of the dollar sign depends on the token it's in. The expression $(command) is a modern synonym for command which stands for command substitution; it means, run command and put its output here.
What you need to perform all the restarts followed by a pause is a loop over the lines in the $(docker ps --format "{{.Names}}" | grep -v somename)" command, and inside the loop, do a docker restart $line and then a sleep 30 (for 30 seconds) command.
Something like this:
items=$(docker ps --format "{{.Names}}" | grep -v somename)
for word in $items
do
docker restart $word
sleep 30
done
Explanation:
items=$(docker ps --format "{{.Names}}" | grep -v somename)
This line sets a string variable named items that contains all the names of containers separated by spaces, as you did in your original command.
for word in $items
automatically splits the string by spaces, giving you a different container name in every iteration of the for loop.
Between
do
and
done
we have the code that is executed with each of the words in the items string, which is the following
docker restart $word
We restart the docker container as you did, but only for one of the containers, its name read from $word.
sleep 30
We sleep for 30 seconds before iterating again over the next $word value.
Single line version
If you want a compact version that you can run as a single line, you can do:
items=$(docker ps --format "{{.Names}}" | grep -v somename);for word in $items; do; docker restart $word; sleep 30; done;
