Remove 'old' docker config files with wildcards and a single command - docker

Question

I'm currently working with docker config files and I'm looking for a way to automate the removal of 'old' config file. I use a script that will update all my config files version with +1;
app1-config-file-1.2.1
app1-config-file-1.2.2
app1-config-file-1.2.3
etc etc.
Now I would like to remove app1-config-file-1.2.2 when app1-config-file-1.2.3 is created.
This command gets me kinda close;
docker config rm $(docker config ls | grep -e 'app1'.*'-1.2.2')
Where 'app1' is the prefix and the '-1.2.2', well, is the version I want to remove.
The thing is that the command above does remove the correct config, but it will also try to remove the following 'configs'
Error response from daemon: access denied
Error: No such config: hours
Error: No such config: ago
Error response from daemon: access denied
Error: No such config: hours
Error: No such config: ago
Which is what comes back from my query:
$(docker config ls | grep -e 'app1'.*'-1.2.2')
I tried adding the --quiet or -q to only get back the config IDs. But for some reason I can't use it with config files the way it works with container.
docker config ls -q | grep -e 'app1'.*'-1.2.2'
results in nothing.
docker config ls | grep -e 'app1'.*'-1.2.2'
results in a list with ID, configfile names, age etc. Basically all the config files I would like to remove, but I just need the ID's
So my question is,
What is the correct way to get the IDs of specific docker config file while using wildcards?
Thank you

Answer 1

When you write
docker config rm $(docker config ls | grep -e 'app1'.*'-1.2.2')
This does three things:
Run docker config ls, producing its formatted output.
Filter (grep) that output to only lines that contain app1...-1.2.2.
Pass the resulting output, split into words, as arguments to docker config rm.
The ... | grep invocation is "dumb" in the sense that it doesn't know anything in particular about the input it has, it just knows that it's lines of text and it should try to filter it.
The better option here is to more directly tell docker config ls what you're looking for. That command takes a --filter option; that's somewhat underdocumented, but if you know the exact name of the config object, you can combine it with --quiet to tell Docker (not the shell) to first filter to a specific config object then only print out its ID.
docker config rm $(docker config ls -f name=app1-config-file-1.2.2 -q)
# But really this is the same as
docker config rm app1-config-file-1.2.2
The "shellier" way is to use another tool to clean up the formatted output. The examples in the Docker documentation show the config ID as the first whitespace-separated column, so you could use awk(1) like
docker config ls | \
grep 'app1.*-1.2.2' | \
awk '{ print $1 }' \
xargs docker config rm
(Other tools work fine here too; personally I'd use sed(1) but it's harder to explain in an SO answer.)