Thursday, July 30, 2015

Picking a language for shell scripting based on its framework ecosystem


  • Do you work somewhere that has a lot of old shell scripts? 
  • Were they all dashed off quickly according to the whims of their original creator - just deploy scripts so maybe they missed some of the care (and documentation) the application code had?
  • Whenever a major revision of said shell scripts is needed, do all of them end up in the bin - sorry trash in case you thought I meant the /usr/bin. Because its easier to write such platform and author specific scripts from scratch than maintain them?

Well the team I recently joined does. So as somebody who personally moved from shell scripts to a shell compatible object orientated scripting language some time ago. Then on to a shell framework, I was asked to assess what to move our menagerie of bash, zshell, cshell, powershell etc. scripts to.

My remit was to recommend a language instead of all those developer specific procedural shell scripts. After all the point of a mainstream language is to introduce cross platform code with a huge set of useful libraries, along with hopefully some standard approaches. Hence get above the sea of shells.

However my preference is to move the team to using a shell framework.

Because what a framework does is give you opinions. It chooses how to do stuff, so you ... and all the developers that come after you, don't have to. In my opinion most of the productivity comes from everyone becoming familiar with the same way of doing things ... whether or not its the best way
(and if it isn't the best way the framework developers spend a lot of time fixing that way with hopefully the minimum of disruption to its API for the end users).

I felt it would be useful to see how active the shell framework ecosystem of a language was, in order to assess how suited to shell scripting it is. Since the goal of a shell framework is essentially the same goal, standardisation of shell scripts. So one indicator for the most suited language is to list the mainstream shell frameworks for the contenders and see which comes out top.

It was decided we will choose from Javascript, Python or Perl. So this is for a team that almost exclusively use Java, which due to its pre-compiled statically typed nature is inherently poorly suited to shell scripting.
Unfortunately Ruby was not to be a candidate. However I have added it anyway, because if its good enough for Amazon, and leading configuration management frameworks such as Puppet ... it should be included.

Strangely it is difficult to find definitive lists of shell frameworks ... perhaps whilst I thought the term had been around for 10 years or more, it has not been coined very effectively ... its not even on Wikipedia ... maybe I made it up! Anyway they exist whether or not there is a proper name for them ... they also often cross over the grey area into being full blown configuration management tools.
So to avoid that argument ... I will add those in as well. I have marked entries with a * where I think it is more a config management tool than a shell framework.

For configuration management systems wikipedia does have an entry ... so using it as a similar benchmark it gives a relative language score of:

Python 11, C 5, Perl 5, Java 4, Ruby 3,
and 1 each for C++, Scala, Erlang, Go and PHP  (none for Javascript)

So on the same sort of  basis I have ranked the languages with the most healthy shell framework ecosystem ... in the belief that it is a good indication that they may be the most suited to being used for shell scripting ...

Python 8

Python has the largest number of well established shell frameworks, as it does in terms of configuration management systems. So on that basis I could award it first prize as the most used language for standardising shell scripting. However numbers are not everything. It doesn't necessarily have the leaders of those two categories of software (see Ruby below)
  1. fabric
  2. cliff
  3. python-deploy-framework
  4. clustershell
  5. builtoncement
  6. ansible *
  7. salt *
  8. bcfg *

Ruby 6

Ruby has capistrano which is possibly the most popular of all shell frameworks, it also has two of the most popular configuration management systems, Puppet and Chef, so on that basis it should perhaps be first or at least joint first with Python. As the most appropriate language for modern shell scripting.

Perl 3

Perl has things that perhaps the other languages don't in related areas. So a number of shell implementations in Perl, and frameworks for writing custom shells. But in terms of what I mean by a shell framework - ie. a tool to run shell commands in a standard way across different servers, shells and platforms it is surprisingly lacking.

Javascript 2

Ummm well Javascript may have broken free of the browser with node.js and other server side runtime environments. But are there any shell frameworks or configuration management systems built with it? ie. tools designed for running shell commands and doing anything other than Javascript installation. Not much TBH and certainly no configuration management engine.
  1. commander.js   (clone of Ruby commander)
  2. shelljs is the leading bunch of utilities for node.js that can act as a shell framework


Conclusion

Its a tie between Python and Ruby, so the decision as to what to go for depends on the individual tools that best suit your shell framework requirements, what they may need to integrate with wrt. configuration management and deployment tools ... plus the existing skills of your developers.
Oh and whether diversity is more important than being the market leader ... or vice versa.

For my own case, Ruby isn't in the running, so that makes it Python based on this premise.
I may follow up this blog post with one comparing the languages wrt. a sample shell script - and see which looks the most maintainable. As a second means of deciding between them.

Note: One other factor is related virtual frameworks ( ... yep made that term up too!)
Basically these wrap up configuration and deployment of virtualised software deployments - either hypervisors or containers - to give a full platform application build - usually for development purposes.
So here Ruby is well ahead with Vagrant along with box grinder

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