mardi 30 juin 2020

Learning openshift: a good moment to revisit awk too

I can’t believe I spent all these years using only grep.

Most of us know how to use awk to print the nth column of a file:

$ awk '{print $1}' /etc/hosts

will print all IP addresses from /etc/hosts

But you can also do filtering before printing the chosen column:

$ awk '$5 >= 2 {print $2}' /path/to/file

will print the second column of all lines, where the 5th column is greater than 2. That would have been hard with grep.

Now I can use that to find out all deployments on my openshift cluster, where the number of current replicas is greater than 2.

$ oc get deployments --all-namespaces | awk '$5 >= 2 {print $2}'
NAME
oauth-openshift
console
downloads
router-default
etcd-quorum-guard
prometheus-adapter
thanos-querier
packageserver

I know that openshift/kubernetes both have a powerful query selector syntax, but for the moment awk will do.

1 commentaire:

Sam Morris a dit…

At work we use both OpenShift and OpenStack. The CLI clients for both can produce JSON output, and so I have found myself leaning heavily on jq for processing their output.

I still haven't bothered using oc's built in golang template or JSONpath output formats!