Recently I started hacking on the Kubernetes (k8s) project. The code base is in Golang and is super fun work on. Development is done via GitHub and Slack.
Kubernetes is a complex project. It is not super big, in terms of line count, approximately 90 000
at the time of writing. The project is moving quite fast, I read today that they are merging about
30 pull requests a day. Development is divided among special interest groups (SIG). New developers
are directed towards SIG/CLI. As you might guess this group takes care of the command line interface
for Kubernetes. K8s clusters are administered via a command line tool called kubectl (pronounced:
‘kube-c-t-l’ or ‘kube control’).
Fast forward one month. I’ve been hacking away merrily now for a while on kubectl. This has lead
me to some interesting open source libraries. The cobra library,
brought to you by the creators of Hugo (the static web site
generator that I am using to write this blog), is one of them.
So, my issue, and the reason I am writing this post, was that I was struggling to decipher the
available options output by use of the --help flag. Of course, first thing I did was throw a pull
request at Kubernetes with a proposed solution. Turns out there may be a more simple solution (remember 50%
of bug fixes introduce more bugs (Steve McConnel)). Introducing
generic colorizer. This awesome tool written by Radovan Garabík
allows you to, as the name suggests, colorize anything.
It is written in Python, you can get install instructions in the repository, or if you are running a
Debian based system just search the package manager for grc. You will need a configuration file in
~/.grc/grc.conf
While we are at it lets colorize go test as well.
# Go
\bgo.* test\b
conf.gotest
# Kubernetes
\bkubectl help\b
conf.kubectlhelp
Colorization is then achieved via regular expressions. You will need a configuration file for each
entry above. Here is conf.kubectlhelp
regexp= \#.*
colour=blue
-
regexp=--.+?(?==)
colour=yellow
-
regexp=^Other Commands
colour=red
-
regexp=^Usage:
color=cyan
-
regexp=^Examples:
color=cyan
-
regexp=^Options:
color=cyan
and conf.gotest
regexp==== RUN .*
colour=blue
-
regexp=--- PASS: .*
colour=green
-
regexp=^PASS$
colour=green
-
regexp=^(ok|\?) .*
colour=magenta
-
regexp=--- FAIL: .*
colour=red
-
regexp=[^\s]+\.go(:\d+)?
colour=cyan
If you like shell aliases you may like to define the following
alias kch='/usr/bin/grc kubectl help'
alias go='/usr/bin/grc go'
voilà kch now presents nice colorized output and you can easily discern the options for whichever
Kubernetes command you are investigating. Bonus points: go test is colorized too.
thanks