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.

mardi 16 juin 2020

Test a webcam from the command line on Linux with VLC

Since this info was too well hidden on the internet, here is the information:
cvlc v4l2:///dev/video0
and there you go.
If you have multiple cameras connected, you can try /dev/video0 up to /dev/video5