“Use Dumb Shell, don’t Reinvent the Wheel”

Opening Rant

You don’t hear one developer saying “Just use Notepad” to a colleague with argumentation that goes roughly like this:

Why are you using this horrible Visual Studio Code? It has built-in debugger! No!

JetBrains IDEs? No! They do too much! They are so into the code!

Vim? Emacs? Not pure enough! Who needs that stupid syntax highlighting?

Keep text editing pure! Any semantic understanding by the text editor is undesirable, other programs should handle that. You don’t want to complicate the text editor.

Developers are not saying that because user experience and productivity matter. Yet, “Use Dumb Shell” is considered to be an acceptable opinion. Is that so common that people fall on their heads so hard (alternatively, did not give it any thought)? WTF?

The solution (shell) should be as simple as possible but not simpler than possible. Current shells are simpler than required by good user experience. Wrong trade-off. Keeping something simple is important but not more important than the outcomes.

Source: https://www.flickr.com/photos/toddle_email_newsletters/15413603567/
Image is a link to http://www.workcompass.com/

Additional food for thought:

  1. Why use a car when bicycle is so much simpler?
  2. Why use electricity when fire is so much simpler?
  3. Why have water in your house when a wells are so much simpler?

Background

I was doing consulting. The usual suspects: AWS, bash, Python, Puppet, Chef. Got to Terraform later. I had and I am still having subpar experiences with these tools. Anything I wanted to do, was overly burdensome, complicated and full of pitfalls.

Since I can’t attempt to fix everything, I picked the worst offender and started working on the alternative programming language and shell combo. The motivating opinion is that Ops have no good programming language nor adequate shell.

The absence of good programming language for ops was covered in another post. In this post I will cover some of the things that are wrong with the interactive shell.

The Shell

The dominant player is bash. It didn’t change much for decades: you type commands and get a dump of text on your screen. Most of the alternatives are essentially the same in this regard, for decades.

Is this because of the brilliant design? I would ask: which design? This? Quoting:

I wrote quite complex shell scripts and my first suggestion is “don’t”. The reason is that is fairly easy to make a small mistake that hinders your script, or even make it dangerous.

The “Dumb Shell” Approach

In this post I would like to address common thought that I hear from people regarding Next Generation Shell, a new programming language and a shell that I’m working on. Note that other shells which are more advanced than POSIX shells also get this. Quoting @cup from lobste.rs:

Wouldnt it be better to just have a dumb shell, that can call programs to do heavy lifting (read: programming languages). This way you have a “division of labor”. Shell works best for launching executables, and programming languages work best for handling data structures and algorithms.

No, it would not. I refuse to accept under-powered tools.

Dumbness is Fundamental Flaw

The “dumb shell” has no semantic understanding and doesn’t care about programs’ inputs nor outputs. Let’s see how it plays out.

Today, “Understanding” of programs’ inputs is covered by completion. Completion was added because “dumb shell” had horrible user experience. It’s slightly better now when the shell “understands” programs’ input to some degree. To some people completion is a scope creep. I think of it as better user experience and productivity gain.

“Understanding” of programs’ outputs? We are not there yet. It also seems that interacting with objects on the screen is too novel of an idea for the shell. Considering how much time this idea is out there: WTF?

Let’s see how this “dumbness” manifests as bad user experience even at the very basic, “intended” functionality:

Programs’ Output – Size

Do you know of any real world scenario when a human supposed to go over 10K lines on the screen? I mean just sit there and read it. Let me know. I’ve never seen such use case.

The shell is dumb, the shell “does not intervene” in programs’ outputs. Sounds good until you get unlimited number of lines dumped on your screen.

“Should have used less” you think later. Right. What if you forgot? The buffer is now filled with useless output and you can’t see outputs of previous programs. Are you being punished? No, just nobody cared about the UX. Alternatively, “it would be to complicated to implement”.

Programs’ Output – All Mixed

  1. Want to know what’s on your screen is stdout and what is stderr? Well… you can’t. Your shell is dumb, it doesn’t deal with things like that.
  2. Want to know from which program the output came from? Nope. Some programs cope with that to some degree by prepending their name to error messages: ls xxx gives you ls: xxx: No such file or directory. What a wonderful strategy! Keep the shell dumb and push the burden to all the programs.
  3. You can’t type because some background job is continuing to dump text on the screen where you are trying to work? Too bad, should have used redirection because guess what … you shell doesn’t handle that either… and you can’t add redirection after the program is running; again not shell’s business.

Programs’ Output – Semantic Understanding

You just typed aws ec2 describe instances --filters ... and now you have some output.

You now see on your screen instance you would like to stop. The ID of the instance is right in front of your face. Now you type aws ec2 stop-instances --instance-ids. You would like to append the instance ID that you see on the screen. Nope. Your shell doesn’t do that. Too dumb. Select with the mouse and paste, because f*ck you!

Side note: amazing AWS engineers did not include any human readable output format so you get JSON dumped on your screen (or any other format which is still non-human-compatible).

Let’s imagine for a moment that the command output had some semantic meaning to the shell.

  1. The shell would display the output as a table.
  2. The table would be interactive (interactive output, what a heresy!) and one could navigate with arrow keys and have a shortcut for copy/paste the current cell value to the command line (for completion).
  3. You could interact with the objects in the table with the mouse (very new concept, another heresy for the shell).
  4. How about instead of typing aws ec2 stop-instances --instance-ids you navigate to the correct line, press enter, choose “stop” from the menu and the command is constructed for you? aws ec2 stop-instances --instance-ids i-123... amazing, ha? Well, your shell can’t do that.

Meaning, do you speak it mo***er?

How about after performing operations using the UI you would get as per your choice one of the below snippets which would re-create the operation:

  1. CLI commands
  2. CloudFormation tempalte
  3. Terraform “code”

Solution: UI for the Shell

Suppose I agree for a second, what do you suggest?

https://github.com/ngs-lang/ngs/wiki/UI-Design

I personally don’t see how the described features could be implemented as external programs, keeping the shell “dumb”.

We Can Do Better Today

The reality has changed. What was once amazing is subpar by today’s standards. The world outside of the shell moved forward while the shell stayed almost the same. Brilliant design? Brilliant what?

Let’s move this industry together from the stone age of bash shell to the bronze age of something a bit less subpar – Next Generation Shell.

Closing Rant

Imaginary UNIX people:

We wanted to separate things because they are semantically different so we split the things into stdout and stderr. Well… stderr was is actually for everything that is not stdout.

One bit of metadata (stdout vs stderr) for semantic meaning of the output should be enough for everyone forever. Well… at least it’s simple for us to implement.


Update: discussion on lobste.rs

AWS CloudFormation became a programming language

… kind of.

Declarative has its advantages which are hyped all over the internet so I’ll skip that part. The painful downside of declarative approach is often the expressivity. Sample proofs:

Now you can have Python embedded in your CloudFormation file. That is part of the CloudFormation Macros which were introduced on 2018-09-06.


Happy coding, everyone!

 

Bash pitfall: if test, if [, if [[

I bet you’ve seen a lot of scripts with seemingly innocent if [ -e blah ];then ...; else ...; fi or something similar . What’s the problem? if has at most two branches while test , [ and [[ have three different exit codes. Oops.

If you make a syntax error (or any other error occurs) in the test , [ or [[ expression, it will return the exit code 2 (or above, according to man test​). if will take the else branch. If you are lucky, you will notice the error message from the test, [ or [[ commands. If not, the else branch will always be executed.

I don’t want to use bash. The pitfall above is one of the many reasons. Unfortunately, I do use bash because it’s still best tool for some tasks. I’m working on alternative to bash. It’s called NGS, the Next Generation Shell. In NGS, the situation above is solved as one would expect from a modern programming language: exit codes 2 and above throw exception.

If you also think that there should be a viable alternative to bash, you are welcome to help me working on it.


Happy coding! Hope it’s not in bash 🙂

Bezeq International “protection”

Hello!

I’ve got “protection” feature by default (and I didn’t notice I even had it up until now) from my internet provider, Bezeq International. In the last few days I was experiencing selective reachability. Some IPs were just blocked by the “protection”.

More than 20 minutes with support that wanted to install their binaries on my laptop (I couldn’t do it for many reasons) and then about 5 minutes with some more senior guy that after hearing the symptoms just turned that thing off. Everything works fine now.

Hope this helps other people so they could recognize the situation and immediately know what’s happening.

Details follow:

  • One of GitHub web IPs was blocked.
  • Broken FaceBook
    ;; ANSWER SECTION:
    static.xx.fbcdn.net. 3599 IN CNAME scontent.xx.fbcdn.net.
    scontent.xx.fbcdn.net. 59 IN A 157.240.1.23
  • Broken AWS. Manifested in timeouts talking to various services endpoints.

Following are just screenshots of http://ec2-reachability.amazonaws.com/ :

 

Screen Shot 2018-07-24 at 9.09.34 AMScreen Shot 2018-07-24 at 9.09.42 AMScreen Shot 2018-07-24 at 9.09.50 AMScreen Shot 2018-07-24 at 9.09.58 AMScreen Shot 2018-07-24 at 9.10.07 AMScreen Shot 2018-07-24 at 9.10.16 AMScreen Shot 2018-07-24 at 9.10.25 AMScreen Shot 2018-07-24 at 9.10.33 AMScreen Shot 2018-07-24 at 9.10.40 AMScreen Shot 2018-07-24 at 9.10.46 AM

Terraform 0.12 language looks bad

I was hoping that smart guys vs bad situation will have another outcome but Terraform language for version 0.12 looks bad… as languages of Puppet and Ansible.

I’m not saying that people that made Puppet and Ansible are not smart. It’s that we could learn from the mistakes they made… unless we don’t consider those being mistakes.

Puppet and Ansible went through very similar difficult situation. They have limited themselves to a declarative format and then they tried to accommodate the real life. Terraform has this situation right now.

The situation is:

  • Declarative format being used
  • People need something more powerful, like a programming language because … real life where conditionals, loops and data transformations make much more sense than working around declarative languages limitations.

Interestingly enough, they all did not switch to a proper programming language. Maybe because that would be at least partially admitting that the product should have been a library in the first place?

Terraform is actually in very crappy situation because even if they decide to expose everything as a library as the main interface, I don’t see people start using Go for “infrastructure as code”. Not as smooth as Ruby or Python anyway.

Happy coding, everyone!

Update (2018-07-21):

On a bit more positive note, the new splat operator looks like an improvement.

Update (2018-07-27):

Terraform looks even more like a “normal” language with Conditional Operator Improvements and null value. The conditional operator fixes previous oddities that it had.

Update (2018-08-02):

Terraform got type system. Looks powerful. Just need to see that Terraform does not evolve to Scala 🙂

Update (2018-08-11):

New template syntax brings more raw power. Looks good.

Update (2018-08-26):

  • HCL to JSON one-to-one mapping. When I read “having a clean 1:1 mapping between HCL and JSON, and ensuring every feature of HCL is supported in JSON” I immediately thought that there must be converting tools then… and was not disappointed 🙂 “In future versions of Terraform, we will also support native tooling to convert HCL to JSON and JSON to HCL cleanly (including comments)”
  • “Comments in JSON” – nice!

 

Terraform becomes a programming language

Declarative languages failure

Approach that in my eyes failed, again and again, is to start with your own declarative language and then with time grow the language. (SQL being among notable exceptions)

Puppet is the best example. map and each, added in Puppet 4.0.0 are, in my opinion, just two in a sea of evidence that the envisioned simple format has failed to handle the needs of the real world.

Ansible’s loop looks bad as the whole idea of making top levels of programs in YAML based syntax (and the rest in Python).

In my opinion, it makes more sense to create a language first and then libraries for it, not a library and then a language around it.

My hope for Terraform

I think Terraform guys are smart. Among other things, it manifests in implementing data sources. Data sources make Terraform much more flexible. I think it’s very clever.

Terraform, which started declarative, are now inventing their own programming language. They are going the way of Puppet and Ansible. I hope they can do better, in this awkward situation: there are quite a lot of constraints on the programming language because of the existing syntax and semantics.

Happy coding, everyone!

 

List of JSON tools for command line

I am considering making a JSON parsing and generating command line tool. Started with looking around a bit. Below is a list of existing JSON command line tools. Numbers are [GitHub stars] at the time of writing this post. (… contributed by …) means that this post was updated with the item.

  • jq [11126] – filter, extract, modify and output JSON or text using DSL
  • jid [4426] – “You can drill down JSON interactively by using filtering queries like jq.” (item contributed by /u/Tacticus)
  • gron [4103] – convert JSON or JSON lines (from file/stdin/url) to text (path=value) which can be processed with grep/sed/diff; the tool also supports converting back to JSON after such processing
  • jo [2209] – generate JSON based on command line arguments and stdin; can read data from files and place it as base64 encoded values
  • JSON.sh [1635] – written in shell/gawk; “traverses the JSON objects and prints out the path to the current object (as a JSON array) and then the object, without whitespace”
  • underscore-cli [1588] ‘THE “Swiss Army knife” tool for processing JSON data – can be used as a simple pretty-printer, or as a full-powered JavaScript command-line’. Added on 2019-09-30 following comment from @joeytwiddle.
  • jsawk [1239] – focused primarily on filtering and transforming a list (or an object). Update 2019-09-30: as @joeytwiddle suggested in comment, the project appears to be unmaintained and doesn’t work with recent Node.js versions. Latest commit and latest closed issue are from 2015.
  • json (by trentm) [1218] – “massaging JSON on your Unix command line”; JS-like syntax for extracting values; in-place file editing
  • rq [1007] – awk/sed-like tool for structured data; supports several formats, including JSON
  • TickTick [469] – use JSON syntax directly in bash; “This is just a fun hack”
  • jshon [309] – very CLI-ish way to extract, manipulate and output the data
  • jl [308] – “a tiny functional language for querying and manipulating JSON”; visually reminds Haskell
  • jsonpp [244] – JSON pretty printer (item contributed by /u/ferbass)
  • fx [227] – conveniently run your JS code to manipulate JSON.
  • RecordStream [224] – create, manipulate and output records; supports JSON; Perl-based so grep expressions for example are in Perl.
  • JSON.awk [186] – JSON.sh fork in awk; after fork the projects added different features.
  • jp [184] – “command line interface to JMESPath” (link contributed by Evgeny Zislis)
  • json-command [143] – conveniently manipulate JSON using JS.
  • jsonv.sh [130] – convert JSON to CSV; specify paths in JSON to
  • jgrep (aka “JSON-grep”) [78] – “Command line tool and API for parsing JSON documents” in Ruby (item contributed by /u/tophlammiepie)
  • jsed [48] – manipulate and extract data; somewhat similar to jsawk in mindset
  • jayin [10] “Piping with js at terminal”. Added on 2019-09-30 following comment from @joeytwiddle.
  • jsongrep [9] (by dsc) – extract data at given path using shell globs and output one per line
  • jc [2] – “jc is used to JSONify the output of many standard linux cli tools”. Added on 2019-10-29 following comment from Kelly Brazil.
  • jsongrep [0] (by terrycojones) – easily extract data at given path

Honorable mentions

Update 2018-09-10:

I’ve added related post in which I argue that jq functionality belongs to a shell.


If you feel that some project is missing from the list, please let me know in comments below.