Enhance your terminal prompt to show current Ruby version

I've you've ever found yourself at a terminal thinking What version of Ruby is currently active? then perhaps this tip is for you. Operating multiple Ruby installations has never been easier thanks to tools like the elegant chruby, which lets you view the status of your Rubies in a single command. But no matter which Ruby manager you use, awareness of your evironment configuration is essential to proper Ruby development! I found myself checking my version so often that it merited some form of automation.

With a little bit of Bash, I came up with a fun solution that anyone can implement (it's just a single line of code!) to permanently populate your shell prompt with this information, turning something like this:

cmptr:dir usr$

into this:

[ruby 2.1.3p242] cmptr:dir usr$

The key to 'hacking' your prompt is setting the variable PS1, ideally in some shell profile that is automatically loaded. To produce a prompt like the one above, use a value of:

PS1="$(tput setaf 1)[$(ruby -v | grep -o 'ruby ([^\( ]*)')]$(tput sgr0) \h:\W \u\$ "

It looks messy but the explanation is simple. The first part is an interpolated command which changes the text color to RED, a totally aesthetic touch you don't really need. I chose red for Ruby, but it doesn't matter.

$(tput setaf 1)

The most reliable way of determining your Ruby version is to run the executable itself, which will output version and build info when passed the -v flag. I pipe this into grep to trim it down to essentials, using the -o flag which makes it return only what matches the given regex. The enclosing brackets are just aesthetic as well here.

[$(ruby -v | grep -o 'ruby ([^\( ]*)')]

Last but not least we reset the coloring, which prevents the rest of the prompt from coming out red.

$(tput sgr0)