Am I crazy in thinking that bash is good enough for production? (lemm.ee)

submitted 2 days ago by Badland9085@lemm.ee to c/programming@programming.dev

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This may make some people pull their hair out, but I’d love to hear some arguments. I’ve had the impression that people really don’t like bash, not from here, but just from people I’ve worked with.

There was a task at work where we wanted something that’ll run on a regular basis, and doesn’t do anything complex aside from reading from the database and sending the output to some web API. Pretty common these days.

I can’t think of a simpler scripting language to use than bash. Here are my reasons:

Reading from the environment is easy, and so is falling back to some value; just do ${VAR:-fallback}; no need to write another if-statement to check for nullity. Wanna check if a variable’s set to something expected? if [[ <test goes here> ]]; then <handle>; fi
Reading from arguments is also straightforward; instead of a import os; os.args[1] in Python, you just do $1.
Sending a file via HTTP as part of an application/x-www-form-urlencoded request is super easy with curl. In most programming languages, you’d have to manually open the file, read them into bytes, before putting it into your request for the http library that you need to import. curl already does all that.
Need to read from a curl response and it’s JSON? Reach for jq.
Instead of having to set up a connection object/instance to your database, give sqlite, psql, duckdb or whichever cli db client a connection string with your query and be on your way.
Shipping is… fairly easy? Especially if docker is common in your infrastructure. Pull Ubuntu or debian or alpine, install your dependencies through the package manager, and you’re good to go. If you stay within Linux and don’t have to deal with differences in bash and core utilities between different OSes (looking at you macOS), and assuming you tried to not to do anything too crazy and bring in necessary dependencies in the form of calling them, it should be fairly portable.

Sure, there can be security vulnerability concerns, but you’d still have to deal with the same problems with your Pythons your Rubies etc.

For most bash gotchas, shellcheck does a great job at warning you about them, and telling how to address those gotchas.

There are probably a bunch of other considerations but I can’t think of them off the top of my head, but I’ve addressed a bunch before.

So what’s the dealeo? What am I missing that may not actually be addressable?

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[-] melezhik@programming.dev 12 points 1 day ago* (last edited 1 day ago)

We are not taking about use of Bash in dev vs use Bash in production. This is imho incorrect question that skirts around the real problem in software development. We talk about use of Bash for simple enough tasks where code is rarely changed ( if not written once and thrown away ) and where every primitive language or DSL is ok, where when it comes to building of medium or complex size software systems where decomposition, complex data structures support, unit tests, error handling, concurrency, etc is a big of a deal - Bash really sucks because it does not allow one to deal with scaling challenges, by scaling I mean where you need rapidly change huge code base according changes of requirements and still maintain good quality of entire code. Bash is just not designed for that.

[-] Badland9085@lemm.ee 6 points 23 hours ago

But not everything needs to scale, at least, if you don’t buy into the doctrine that everything has to be designed and written to live forever. If robust, scalable solutions is the nature of your work and there’s nothing else that can exist, then yeah, Bash likely have no place in that world. If you need any kind of handling more complicated than just getting an error and doing something else, then Bash is not it.

Just because Bash isn’t designed for something you want to do, doesn’t mean it sucks. It’s just not the right tool. Just because you don’t practice law, doesn’t mean you suck; you just don’t do law. You can say that you suck at law though.

[-] melezhik@programming.dev 4 points 14 hours ago* (last edited 14 hours ago)

Yep. Like said - "We talk about use of Bash for simple enough tasks ... where every primitive language or DSL is ok", so Bash does not suck in general and I myself use it a lot in proper domains, but I just do not use it for tasks / domains with complexity ( in all senses, including, but not limited to team work ) growing over time ...

[-] tleb@lemmy.ca 7 points 19 hours ago

If your company ever has >2 people, it will become a problem.

[-] Badland9085@lemm.ee 1 points 8 hours ago

You’re speaking prophetically there and I simply do not agree with that prophecy.

If you and your team think you need to extend that bash script to do more, stop and consider writing it in some other languages. You’ve move the goalpost, so don’t expect that you can just build on your previous strategy and that it’ll work.

If your “problem” stems from “well your colleagues will not likely be able to read or write bash well enough”, well then just don’t write it in bash.

[-] furrowsofar@beehaw.org 9 points 1 day ago

Just make certain the robustness issues of bash do not have security implications. Variable, shell, and path evalutions can have security issues depending on the situation.

[-] Badland9085@lemm.ee 2 points 1 day ago

Certainly so. The same applies to any languages we choose, no?

[-] furrowsofar@beehaw.org 8 points 1 day ago* (last edited 1 day ago)

Bash is especially suseptable. Bash was intended to be used only in a secure environment including all the inputs and data that is processed and including all the proccess on the system containing the bash process in question for that matter. Bash and the shell have a large attack surface. This is not true for most other languages. It is also why SUID programs for example should never call the shell. Too many escape options.

[-] Badland9085@lemm.ee 1 points 8 hours ago

Good point. It’s definitely something to keep in mind about. It’s pretty standard procedure to secure your environments and servers, wherever arbitrary code can be ran, lest they become grounds for malicious actors to use your resources for their own gains.

What could be a non-secure environment where you can run Bash be like? A server with an SSH port exposed to the Internet with just password authentication is one I can think of. Are there any others?

[-] furrowsofar@beehaw.org 2 points 8 hours ago* (last edited 7 hours ago)

By the way, I would not consider logging in via ssh and running a bash script to be insecure in general.

However taking uncontrolled data from outside of that session and injecting it could well be insecure as the data is probably crossing an important security boundary.

[-] furrowsofar@beehaw.org 2 points 8 hours ago* (last edited 8 hours ago)

I was more thinking of the CGI script vunerability that showed up a few years ago. In that case data came from the web into the shell environment uncontrolled. So uncontrolled data processing where the input data crosses security boundaries is an issue kind of like a lot of the SQL injection attacks.

Another issue with the shell is that all proccesses on the system typically see all command line arguments. This includes any commands the shell script runs. So never specify things like keys or PII etc as command line arguments.

Then there is the general robustness issue. Shell scripts easy to write to run in a known environment and known inputs. Difficult to make general. So for fixed environment and known and controlled inputs that do not cross security boundaries probaby fine. Not that, probablay a big issue.

By the way, I love bash and shell scripts.

[-] vext01@lemmy.sdf.org 25 points 1 day ago

Honestly, if a script grows to more than a few tens of lines I'm off to a different scripting language because I've written enough shell script to know that it's hard to get right.

Shellcheck is great, but what's greater is a language that doesn't have as many gotchas from the get go.

[-] zygo_histo_morpheus@programming.dev 18 points 1 day ago

One thing that I don't think anyone else has mentioned is data structures. Bash does have arrays and hashmaps at least but I've found that working with them is significantly more awkward than in e.g. python. This is one of several reasons for why bash doesn't scale up well, but sure for small enough scripts it can be fine (if you don't care about windows)

[-] syklemil@discuss.tchncs.de 6 points 1 day ago

I think I mentioned it, but inverse: The only data type I'm comfortable with in bash are simple string scalars; plus some simple integer handling I suppose. Once I have to think about stuff like "${foo[@]}" and the like I feel like I should've switched languages already.

Plus I rarely actually want arrays, it's way more likely I want something in the shape of

@dataclass(frozen=True)
class Foo:
    # …

foos: set[Foo] = …

[-] lurklurk@lemmy.world 1 points 14 hours ago

I use the same heuristic... if I need a hashmap or more complex math, I need a different language

Also if the script grows beyond 100 lines, I stop and think about what I'm doing. Sometimes it's OK, but it's a warning flag

[-] syklemil@discuss.tchncs.de 2 points 13 hours ago

Yeah agreed on the 100 lines, or some other heuristic in the direction of "this script will likely continue to grow in complexity and I should switch to a language that's better suited to handle that complexity".

[-] Badland9085@lemm.ee 3 points 1 day ago

That’s definitely worth mentioning indeed. Bash variables, aside from arrays and hashmaps that you get with declare, are just strings. Any time you need to start capturing a group of data and do stuff with them, it’s a sign to move on. But there are many many times where that’s unnecessary.

[-] ShawiniganHandshake@sh.itjust.works 20 points 1 day ago

I've worked in bash. I've written tools in bash that ended up having a significant lifetime.

Personally, you lost me at

reading from the database

Database drivers exist for a reason. Shelling out to a database cli interface is full of potential pitfalls that don't exist in any language with a programmatic interface to the database. Dealing with query parameterization in bash sounds un-fun and that's table stakes, security-wise.

Same with making web API calls. Error handling in particular is going to require a lot of boilerplate code that you would get mostly for free in languages like Python or Ruby or Go, especially if there's an existing library that wraps the API you want to use in native language constructs.

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[-] FizzyOrange@programming.dev 22 points 2 days ago

I'm afraid your colleagues are completely right and you are wrong, but it sounds like you genuinely are curious so I'll try to answer.

I think the fundamental thing you're forgetting is robustness. Yes Bash is convenient for making something that works once, in the same way that duct tape is convenient for fixes that work for a bit. But for production use you want something reliable and robust that is going to work all the time.

I suspect you just haven't used Bash enough to hit some of the many many footguns. Or maybe when you did hit them you thought "oops I made a mistake", rather than "this is dumb; I wouldn't have had this issue in a proper programming language".

The main footguns are:

Quoting. Trust me you've got this wrong even with shellcheck. I have too. That's not a criticism. It's basically impossible to get quoting completely right in any vaguely complex Bash script.
Error handling. Sure you can set -e, but then that breaks pipelines and conditionals, and you end up with really monstrous pipelines full of pipefail noise. It's also extremely easy to forget set -e.
General robustness. Bash silently does the wrong thing a lot.

instead of a import os; os.args[1] in Python, you just do $1

No. If it's missing $1 will silently become an empty string. os.args[1] will throw an error. Much more robust.

Sure, there can be security vulnerability concerns, but you’d still have to deal with the same problems with your Pythons your Rubies etc.

Absolutely not. Python is strongly typed, and even statically typed if you want. Light years ahead of Bash's mess. Quoting is pretty easy to get right in Python.

I actually started keeping a list of bugs at work that were caused directly by people using Bash. I'll dig it out tomorrow and give you some real world examples.

[-] lurklurk@lemmy.world 1 points 15 hours ago

I don't disagree with your point, but how does set -e break conditionals? I use it all the time without issues

Pipefail I don't use as much so perhaps that's the issue?

[-] FizzyOrange@programming.dev 1 points 8 hours ago

It means that all commands that return a non-zero exit code will fail the script. The problem is that exit codes are a bit overloaded and sometimes non-zero values don't indicate failure, they indicate some kind of status. For example in git diff --exit-code or grep.

I think I was actually thinking of pipefail though. If you don't set it then errors in pipelines are ignored, which is obviously bad. If you do then you can't use grep in pipelines.

[-] lurklurk@lemmy.world 1 points 7 hours ago

My sweet spot is set -ue because I like to be able to use things like if grep -q ...; then and I like things to stop if I misspelled a variable.

It does hide failures in the middle of a pipeline, but it's a tradeoff. I guess one could turn it on and off when needed

[-] JamonBear@sh.itjust.works 5 points 1 day ago

Agreed.

Also gtfobins is a great resource in addition to shellcheck to try to make secure scripts.

For instance I felt upon a script like this recently:

#!/bin/bash
# ... some stuff ...
tar -caf archive.tar.bz2 "$@"

Quotes are OK, shellcheck is happy, but, according to gtfobins, you can abuse tar, so running the script like this: ./test.sh /dev/null --checkpoint=1 --checkpoint-action=exec=/bin/sh ends up spawning an interactive shell...

So you can add up binaries insanity on top of bash's mess.

[-] lurklurk@lemmy.world 2 points 15 hours ago

I imagine adding -- so it becomes tar -caf archive.tar.bz2 -- "$@" would fix that specific case

But yeah, putting bash in a position where it has more rights than the user providing the input is a really bad idea

[-] syklemil@discuss.tchncs.de 1 points 13 hours ago

Quotes are OK, shellcheck is happy, but, according to gtfobins, you can abuse tar, so running the script like this: ./test.sh /dev/null --checkpoint=1 --checkpoint-action=exec=/bin/sh ends up spawning an interactive shell…

This runs into a part of the unix philosophy about doing one thing and doing it well: Extending programs to have more (absolutely useful) functionality winds up becoming a security risk. The shell is generally geared towards being a collection of shortcuts rather than a normal, predictable but tedious API.

For a script like that you'd generally want to validate that the input is actually what you expect if it needs to handle hostile users, though. It'll likely help the sleepy users too.

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[-] Die4Ever@programming.dev 41 points 2 days ago

I just don't think bash is good for maintaining the code, debugging, growing the code over time, adding automated tests, or exception handling

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[-] jollyroberts@jolly-piefed.jomandoa.net 39 points 2 days ago

"Use the best tool for the job, that the person doing the job is best at." That's my approach.

I will use bash or python dart or whatever the project uses.

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this post was submitted on 15 Jan 2025

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