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by ris 1777 days ago
Speaking as a long-time python developer...

If you actually "get into" jq you find out that it's a significantly neater language than it appears on the surface. Firstly it does allow you write multi-line scripts, and things start to look a lot neater once you do. Secondly it's actually a real, working, functional programming language, which allows very succinct expression of ideas which, in python, would likely require the reader to track state across explicit loops and the like.

Once you dig into the manual, you also tend to discover that a lot of the things that cause you to string multiple jq invocations together aren't actually necessary because there are quite sensible ways of handling them in-language.

It's quite laughable though to tout python over jq because of it adding a dependency. Perhaps if you're already embedded in python-land and all your environments already have python - but many (most?) of us are increasingly targeting extremely minimal container image environments. In that case, adding python is a much larger and more complex dependency than jq's single 3.8MB binary.

As someone who has to read an awful lot of other peoples deployment scripts, it's also quite nice when I see jq because it loudly advertises "all I'm doing here is mangling one piece of json into another! no side effects!". I'd much rather follow the thread of execution into that than some mystery ruby script any day.

1 comments

> Secondly it's actually a real, working, functional programming language, which allows very succinct expression of ideas which, in python, would likely require the reader to track state across explicit loops and the like.

This is the problem. Is yet another language that someone has to learn and know, like the ton of other UNIX commands that have their own DSL.

> Once you dig into the manual, you also tend to discover that a lot of the things that cause you to string multiple jq invocations together aren't actually necessary because there are quite sensible ways of handling them in-language.

Nice. I can dig into the manual and spend a day to learn it, but I don't have that time. I have a script to fix, I know how to program in python, and throw away the jq code and substitute it with 10 lines of python in a minute, and problems solved.

> It's quite laughable though to tout python over jq because of it adding a dependency

If jq enters your codebase then everywhere you have to install it. It's not that difficult (but not trivial on Windows), but it is annoying, you run a script and you then find out that you don't have jq installed and you need to install it.

Also what is faster: eliminating the need for the jq command in a script, or installing jq on tens of different systems with different operating systems?

No, where I work I established a rule that every script should be written in python and should use only the standard library, with a few exception (e.g. we work with AWS so boto3 is an exception). If not every developer did use whatever tool they thought it was cool (like jq), write a ton of bash spaghetti code with all these tools used together, and forced every other developer to install them on their system (and cause a lot of work to the IT, i.e. me to do so if they weren't able and fix all the problem).

> Perhaps if you're already embedded in python-land and all your environments already have python

Python is everywhere. Every Linux distribution have a python interpreter in them, same for macOS, and in Windows nowadays you install directly from the store with one click. The problem is that if jq enters the codebase then of course every developer machine has to have it installed. This is annoying.

I sympathize with both points of view. I think of autotools as an extreme example of how less general tools tend to grow in complexity to the point that the effort to learn them outweighs the benefit you get from knowing them well. But there is something missing from the "just use python everywhere" argument as well. For many usecases, choosing a less expressive language can guard against excessive complexity creeping in at that layer. IMO, json+jq fills a useful niche between semistructured/unstructured-text+awk/sed/bash and APIs+some-gp-scripting-language