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-urlencodedrequest is super easy withcurl. 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.curlalready does all that. - Need to read from a
curlresponse and it’s JSON? Reach forjq. - Instead of having to set up a connection object/instance to your database, give
sqlite,psql,duckdbor 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
Ubuntuordebianoralpine, 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?
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 ofpipefailnoise. It’s also extremely easy to forgetset -e. - General robustness. Bash silently does the wrong thing a lot.
instead of a
import os; os.args[1]in Python, you just do$1No. If it’s missing
$1will silently become an empty string.os.args[1]will throw an error. Much more robust.Sure, there can be security vulnerability concerns, but you’d still have to deal with the same problems with your Pythons your Rubies etc.
Absolutely not. Python is strongly typed, and even statically typed if you want. Light years ahead of Bash’s mess. Quoting is pretty easy to get right in Python.
I actually started keeping a list of bugs at work that were caused directly by people using Bash. I’ll dig it out tomorrow and give you some real world examples.
Agreed.
Also gtfobins is a great resource in addition to shellcheck to try to make secure scripts.
For instance I felt upon a script like this recently:
#!/bin/bash # ... some stuff ... tar -caf archive.tar.bz2 "$@"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/shends up spawning an interactive shell…So you can add up binaries insanity on top of bash’s mess.
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.
gtfobins
Meh, most in that list are just “if it has the SUID bit set, it can be used to break out of your security context”.
I imagine adding
--so it becomestar -caf archive.tar.bz2 -- "$@"would fix that specific caseBut yeah, putting bash in a position where it has more rights than the user providing the input is a really bad idea
I don’t disagree with your point, but how does
set -ebreak conditionals? I use it all the time without issuesPipefail I don’t use as much so perhaps that’s the issue?
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-codeorgrep.I think I was actually thinking of
pipefailthough. If you don’t set it then errors in pipelines are ignored, which is obviously bad. If you do then you can’t usegrepin pipelines.
I honestly don’t care about being right or wrong. Our trade focuses on what works and what doesn’t and what can make things work reliably as we maintain them, if we even need to maintain them. I’m not proposing for bash to replace our web servers. And I certainly am not proposing that we can abandon robustness. What I am suggesting that we think about here, is that when you do not really need that robustness, for something that may perhaps live in your production system outside of user paths, perhaps something that you, your team, and the stakeholders of the particular project understand that the solution is temporary in nature, why would Bash not be sufficient?
I suspect you just haven’t used Bash enough to hit some of the many many footguns.
Wrong assumption. I’ve been writing Bash for 5-6 years now.
Maybe it’s the way I’ve been structuring my code, or the problems I’ve been solving with it, in the last few years after using
shellcheckandbash-language-serverthat I’ve not ran into issues where I get fucked over by quotes.But I can assure you that I know when to dip and just use a “proper programming language” while thinking that Bash wouldn’t cut it. You seem to have an image of me just being a “bash glorifier”, and I’m not sure if it’ll convince you (and I would encourage you to read my other replies if you aren’t), but I certainly don’t think bash should be used for everything.
No. If it’s missing
$1will silently become an empty string.os.args[1]will throw an error. Much more robust.You’ll probably hate this, but you can use
set -uto catch unassigned variables. You should also use fallbacks wherever sensible.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.
Not a good argument imo. It eliminates a good class of problems sure. But you can’t eliminate their dependence on shared libraries that many commands also use, and that’s what my point was about.
And I’m sure you can find a whole dictionary’s worth of cases where people shoot themselves in the foot with bash. I don’t deny that’s the case. Bash is not a good language where the programmer is guarded from shooting themselves in the foot as much as possible. The guardrails are loose, and it’s the script writer’s job to guard themselves against it. Is that good for an enterprise scenario, where you may either blow something up, drop a database table, lead to the lost of lives or jobs, etc? Absolutely not. Just want to copy some files around and maybe send it to an internal chat for regular reporting? I don’t see why not.
Bash is not your hammer to hit every possible nail out there. That’s not what I’m proposing at all.
And I certainly am not proposing that we can abandon robustness.
If you’re proposing Bash, then yes you are.
You’ll probably hate this, but you can use set -u to catch unassigned variables.
I actually didn’t know that, thanks for the hint! I am forced to use Bash occasionally due to misguided coworkers so this will help at least.
But you can’t eliminate their dependence on shared libraries that many commands also use, and that’s what my point was about.
Not sure what you mean here?
Just want to copy some files around and maybe send it to an internal chat for regular reporting? I don’t see why not.
Well if it’s just for a temporary hack and it doesn’t matter if it breaks then it’s probably fine. Not really what is implied by “production” though.
Also even in that situation I wouldn’t use it for two reasons:
- “Temporary small script” tends to smoothly morph into “10k line monstrosity that the entire system depends on” with no chance for rewrites. It’s best to start in a language that can cope with it.
- It isn’t really any nicer to use Bash over something like Deno. Like… I don’t know why you ever would, given the choice. When you take bug fixing into account Bash is going to be slower and more painful.
I’m going to downvote your comment based on that first quote reply, because I think that’s an extreme take that’s unwarranted. You’ve essentially dissed people who use it for CI/CD and suggested that their pipeline is not robust because of their choice of using Bash at all.
And judging by your second comment, I can see that you have very strong opinions against bash for reasons that I don’t find convincing, other than what seems to me like irrational hatred from being rather uninformed. It’s fine being uninformed, but I suggest you tame your opinions and expectations with that.
About shared libraries, many popular languages, Python being a pretty good example, do rely on these to get performance that would be really hard to get from their own interpreters / compilers, or if re-implementing it in the language would be pretty pointless given the existence of a shared library, which would be much better scrutinized, is audited, and is battle-tested. libcrypto is one example. Pandas depends on NumPy, which depends on, I believe, libblas and liblapack, both written in C, and I think one if not both of these offer a cli to get answers as well. libssh is depended upon by many programming languages with an ssh library (though there are also people who choose to implement their own libssh in their language of choice). Any vulnerabilities found in these shared libraries would affect all libraries that depend on them, regardless of the programming language you use.
If production only implies systems in a user’s path and not anything else about production data, then sure, my example is not production. That said though, I wouldn’t use bash for anything that’s in a user’s path. Those need to stay around, possible change frequently, and not go down. Bash is not your language for that and that’s fine. You’re attacking a strawman that you’ve constructed here though.
If your temporary small script morphs into a monster and you’re still using bash, bash isn’t at fault. You and your team are. You’ve all failed to anticipate that change and misunderstood the “temporary” nature of your script, and allowed your “temporary thing” to become permanent. That’s a management issue, not a language choice. You’ve moved that goalpost and failed to change your strategy to hit that goal.
You could use Deno, but then my point stands. You have to write a function to handle the case where an env var isn’t provided, that’s boilerplate. You have to get a library for, say, accessing contents in Azure or AWS, set that up, figure out how that api works, etc, while you could already do that with the awscli and probably already did it to check if you could get what you want. What’s the syntax for
mkdir? What’s it formkdir -p? What about other options? If you already use the terminal frequently, some of these are your basic bread and butter and you know them probably by heart. Unless you start doing that with Deno, you won’t reach the level of familiarity you can get with the shell (whichever shell you use ofc).And many argue against bash with regards to error handling. You don’t always need something that proper language has. You don’t always need to handle every possible error state differently, assuming you have multiple. Did it fail? Can you tolerate that failure? Yup? Good. No? Can you do something else to get what you want or make it tolerable? Yes? Good. No? Maybe you don’t want to use bash then.
You’ve essentially dissed people who use it for CI/CD and suggested that their pipeline is not robust because of their choice of using Bash at all.
Yes, because that is precisely the case. It’s not a personal attack, it’s just a fact that Bash is not robust.
You’re trying to argue that your cardboard bridge is perfectly robust and then getting offended that I don’t think you should let people drive over it.
About shared libraries, many popular languages, Python being a pretty good example, do rely on these to get performance that would be really hard to get from their own interpreters / compilers, or if re-implementing it in the language would be pretty pointless given the existence of a shared library, which would be much better scrutinized, is audited, and is battle-tested. libcrypto is one example. Pandas depends on NumPy, which depends on, I believe, libblas and liblapack, both written in C, and I think one if not both of these offer a cli to get answers as well. libssh is depended upon by many programming languages with an ssh library (though there are also people who choose to implement their own libssh in their language of choice). Any vulnerabilities found in these shared libraries would affect all libraries that depend on them, regardless of the programming language you use.
You mean “third party libraries” not “shared libraries”. But anyway, so what? I don’t see what that has to do with this conversation. Do your Bash scripts not use third party code? You can’t do a lot with pure Bash.
If your temporary small script morphs into a monster and you’re still using bash, bash isn’t at fault. You and your team are.
Well that’s why I don’t use Bash. I’m not blaming it for existing, I’m just saying it’s shit so I don’t use it.
You could use Deno, but then my point stands. You have to write a function to handle the case where an env var isn’t provided, that’s boilerplate.
Handling errors correctly is slightly more code (“boilerplate”) than letting everything break when something unexpected happens. I hope you aren’t trying to use that as a reason not to handle errors properly. In any case the extra boilerplate is…
Deno.env.get("FOO"). Wow.What’s the syntax for mkdir? What’s it for mkdir -p? What about other options?
await Deno.mkdir("foo"); await Deno.mkdir("foo", { recursive: true });What’s the syntax for a dictionary in Bash? What about a list of lists of strings?
- Quoting. Trust me you’ve got this wrong even with
I agree with your points, except if the script ever needs maintaining by someone else’s they will curse you and if it gets much more complicated it can quickly become spaghetti. But I do have a fair number of bash scripts running on cron jobs, sometimes its simplicity is unbeatable!
Personally though the language I reach for when I need a script is Python with the click library, it handles arguments and is really easy to work with. If you want to keep python deps down you can also use the sh module to run system commands like they’re regular python, pretty handy
Those two libraries actually look pretty good, and seems like you can remove a lot of the boilerplate-y code you’d need to write without them. I will keep those in mind.
That said, I don’t necessarily agree that bash is bad from a maintainability standpoint. In a team where it’s not commonly used, yeah, nobody will like it, but that’s just the same as nobody would like it if I wrote in some language the team doesn’t already use? For really simple, well-defined tasks that you make really clear to stakeholders that complexity is just a burden for everyone, the code should be fairly simple and straightforward. If it ever needs to get complicated, then you should, for sure, ditch bash and go for a larger language.
That said, I don’t necessarily agree that bash is bad from a maintainability standpoint.
My team uses bash all the time, but we agree (internally as a team) that bash is bad from a maintainability perspective.
As with any tool we use, some of us are experts, and some are not. But the non-experts need tools that behave themselves on days when experts are out of office.
We find that bash does very well when each entire script has no need for branching logic, security controls, or error recovery.
So we use substantial amounts of bash in things like CI/CD pipelines.
Hell, I hate editing bash scripts I’ve written. The syntax just isn’t as easy
I just don’t think bash is good for maintaining the code, debugging, growing the code over time, adding automated tests, or exception handling
If you need anything that complex and that it’s critical for, say, customers, or people doing things directly for customers, you probably shouldn’t use bash. Anything that needs to grow? Definitely not bash. I’m not saying bash is what you should use if you want it to grow into, say, a web server, but that it’s good enough for small tasks that you don’t expect to grow in complexity.
it’s (bash) good enough for small tasks that you don’t expect to grow in complexity.
I don’t think you’ll get a lot of disagreement on that, here. As mention elsewhere, my team prefers bash for simple use cases (and as their bash-hating boss, I support and agree with how and when they use bash.)
But a bunch of us draw the line at database access.
Any database is going to throw a lot of weird shit at the bash script.
So, to me, a bash script has grown to unacceptable complexity on the first day that it accesses a database.
We have dozens of bash scripts running table cleanups and maintenece tasks on the db. In the last 20 years these scripts where more stable than the database itself (oracle -> mysql -> postgres).
But in all fairness they just call the cliclient with the appropiate sql and check for the response code, generating a trap.
That’s a great point.
I post long enough responses already, so I didn’t want to get into resilience planning, but your example is a great highlight that there’s rarely hard and fast rules about what will work.
There certainly are use cases for bash calling database code that make sense.
I don’t actually worry much when it’s something where the first response to any issue is to run it again in 15 minutes.
It’s cases where we might need to do forensic analysis that bash plus SQL has caused me headaches.
Yeah, if it feels like a transaction would be helpful, at least go for pl/sql and save yourself some pain. Bash is for system maintenance, not for business logic.
Heck, I wrote a whole monitoring system for a telephony switch with nothing more than bash and awk and it worked better than the shit from the manufacturer, including writing to the isdn cards for mobile messaging. But I wouldn’t do that again if I have an alternative.
Bash is for system maintenance, not for business logic.
That is such a good guiding principle. I’m gonna borrow that.
small tasks that you don’t expect to grow in complexity
On one conference I heard saying: " There is no such thing as temporary solution and there is no such thing as proof of concept". It’s overexaguration of course but it has some truth to it - there’s a high chance that your “small change” or PoC will be used for the next 20 years so write it as robust and resilient as possible and document it. In other words everything will be extendended, everything will be maintained, everything will change hands.
So to your point - is bash production ready? Well, depends. Do you have it in git? Is it part of some automation pipeline? Is it properly documented? Do you by chance have some tests for it? Then yes, it’s production ready.
If you just “write this quick script and run it in cron” then no. Because in 10 years people will pull their hair screaming “what the hell is hapenning?!”
I find it disingenuous to blame it on the choice of bash being bad when goalposts are moved. Solutions can be temporary as long as goalposts aren’t being moved. Once the goalpost is moved, you have to re-evaluate whether your solution is still sufficient to meet new needs. If literally everything under the sun and out of it needs to be written in a robust manner to accommodate moving goalposts, by that definition, nothing will ever be sufficient, unless, well, we’ve come to a point where a human request by words can immediately be compiled into machine instructions to do exactly what they’ve asked for, without loss of intention.
That said, as engineers, I believe it’s our responsibility to identify and highlight severe failure cases given a solution and its management, and it is up to the stakeholders to accept those risks. If you need something running at 2am in the morning, and a failure of that process would require human intervention, then maybe you should consider not running it at 2am, or pick a language with more guardrails.
A few responses for you:
- I deeply despise
bash. That Linux shell defaults settled on it is an embarrassment to the entire open source community. - Yes, Bash is good enough for production. It is the world’s current default shell. As long as we avoid it’s fancier features (which all suck for production use), a quick bash script is often the most reasonable choice.
- For the love of all that is holy, put your own personal phone number and no one else’s in the script, if you choose to use
bashto access a datatbase. There’s thousands of routine ways that database access can hiccup, and bash is suitable to help you diagnose approximately 0% of them. - If I found out a colleague had used bash for database access in a context that I would be expected to co-maintain, I would start by plotting their demise, and then talk myself down to having a severe conversation with them - after I changed it immediately to something else, in production, ignoring all change protocols.
Could you explain those db connection hiccups you’ve seen?
Sure.
I’ll pick on
postgresbecause it’s popular. But I have found that most databases have a similar number of error codes.https://www.postgresql.org/docs/current/errcodes-appendix.html
It’s not an specific error that’s the issue, it’s the sheer variety of ways things can go wrong, combined with bash not having been architected with the database access use case in mind.
I find this argument somewhat weak. You are not going to run into the vast majority of those errors (in fact, some of them are not even errors, and you will probably never run into some of those errors as Postgres will not return them, eg some error codes from the sql standard). Many of them will only trigger if you do specific things: you started a transaction, you’ll have to handle the possible errors that comes with having a transaction.
There are lots of reasons to never use bash to connect to a db to do things. Here are a couple I think of that I think are fairly basic that some may think they can just do in bash.
- Write to more than 1 table.
- Write to a table that has triggers, knowing that you may get a trigger failure.
- Use transactions.
- Calling a stored procedure that will raise exceptions.
- Accepting user input to write that into a table.
One case that I think is fine to use bash and connect to a db is when all you need to do a
SELECT. You can test your statement in your db manager of choice, and bring that into bash. If you need input sanitization to filter results, stop, and use a language with a proper library. Otherwise, all the failure cases I can think of are: a) connection fails for whatever reason, in which case you don’t get your data, you get an exit code of 1, log to stderr, move on, b) your query failed cause of bad sql, in which case, well, go back to your dev loop, no?This is why I asked what sort of problems have you ran into before, assuming you haven’t been doing risky things with the connection. I’m sorry, but I must say that I’m fairly disappointed by your reply.
I find this argument somewhat weak.
Lol. Me too. I was just trying to give the shorthand version.
Your explanation is much better.
Edit: but it doesn’t sound like you really needed a detailed answer from me, anyway.
I actually love listening to or reading someone else’s war story, and tbh the entire purpose of this post is to dig those up. Bash is one of those places where a lot about it is passed around as tribal knowledge. So I’d really love to hear how things have failed.
Fair enough.
Here’s what I remember: invoking
SQLcontaining inserts frombashhas resulted in lost data, when fairly unsurprising database things happened, sincebashdidn’t really expect to be in charge of logging the details of the attempted change. For the error, it wasn’t something surprising - maybe it was “max connections reached”, stuff that will just happen sometimes.The data loss was probably solveable in
bash, but the scripter didn’t think to (and probably would have needed more effort in a full development tool).
Why internet man hate Bash? Bash do many thing. Make computer work.
I actually (also) love
bash, and use it like crazy.What I really hate is that
bashis so locked in legacy that it’s bad features (on a scripting language scale, which isn’t fair) (and of which there are too many to enumerate) are now locked in permanently.I also hate how convention has kept other shells from replacing bash’s worst features with better modern alternatives.
To some extent, I’m railing against how hard it is to write a good Lexer and a Parser, honestly. Now that bash is stable, there’s little interest in improving it. Particularly since one can just invoke a better scripting language for complex work.
I mourn the sweet spot that Perl occupies, that Bash and Python sit on either side of, looking longingly across the gap that separated their practical use cases.
I have lost hope that Python will achieve shell script levels of pragmatism. Although the
invokelibrary is a frigging cool attempt.But I hold on to my sorrow and anger that Bash hasn’t bridged the gap, and never will, because whatever it can invoke, it’s methods of responding to that invocation are trapped in messes like “if…fi”.
What do you suppose bash could do here? When a program reaches some critical mass in terms of adoption, all your bugs and features are features of your program, and, love it or hate it, somebody’s day is going to be ruined if you do your bug fixes, unless, of course, it’s a fix for something that clearly doesn’t work in the very sense of the word.
I’m sure there’s space for a clear alternative to arise though, as far as scripting languages go. Whether we’ll see that anytime soon is hard to tell, cause yeah, a good lexer and parser in the scripting landscape is hard work.
What do you suppose bash could do here?
- For the love of all that is holy, it’s not 1970, we don’t need to continue to tolerate “if … fi”
- Really everything about how bash handles logic bridging multiple lines of a file. (loops, error handling, etc)
I’m sure there’s space for a clear alternative to arise though, as far as scripting languages go.
The first great alternative/attempt does exist, in
PowerShell. (Honorable mention to Zsh, but I find it has most of the same issues as bash without gaining the killer features of pwsh.)But I’m a cranky old person so I despise (and deeply appreciate!) PowerShell for a completely different set of reasons.
At the moment I use whichever gets the job done, but I would love to stop switching quite so often.
I hold more hope that PowerShell will grow to bridge the gap than that a fork of bash will. The big thing PowerShell lacks is bash’s extra decades of debugging and refinement.
- I deeply despise
Bash is perfectly good for what you’re describing.
Serious question (as a bash complainer):
Have I missed an amazing bash library for secure database access that justifies a “perfectly good” here?
Every database I know comes with an SQL shell that takes commands from stdin and writes query results to stdout. Remember that “bash” never means bash alone, but all the command line tools from cut via jq to awk and beyond … so, that SQL shell would be what you call “bash library”.
Thank you. I wasn’t thinking about that. That’s a great point.
As long as any complex recovery logic fits inside the SQL, itself, I don’t have any issue invoking it from
bash.It’s when there’s complicated follow-up that needs to happen in bash that I get anxious about it, due to past painful experiences.
Right, that’s when you should look for a driver language that’s better suited for the job, e. g. Python.
It’s ok for very small scripts that are easy to reason through. I’ve used it extensively in CI/CD, just because we were using Jenkins for that and it was the path of least resistance. I do not like the language though.
I don’t disagree with this, and honestly I would probably support just using bash like you said if I was in a team where this was suggested.
I think no matter how simple a task is there are always a few things people will eventually want to do with it:
- Reproduce it locally
- Run unit tests, integration tests, smoke tests, whatever tests
- Expand it to do more complex things or make it more dynamic
- Monitor it in tools like Datadog
If you have a whole project already written in Python, Go, Rust, Java, etc, then just writing more code in this project might be simpler, because all the tooling and methodology is already integrated. A script might not be so present for many developers who focus more on the code base, and as such out of sight out of mind sets in, and no one even knows about the script.
There is also the consideration that many people simply dislike bash since it’s an odd language and many feel it’s difficult to do simple things with it.
due to these reasons, although I would agree with making the script, I would also be inclined to have the script temporarily while another solution is being implemented.
May I introduce you to rust script? Basically a wrapper to run rust scripts right from the command line. They can access the rust stdlib, crates, and so on, plus do error handling and much more.
Basically a wrapper to run rust scripts right from the command line.
Isn’t that just Python? :v
Yeah, sometimes I’ll use that just to have the sane control flow of Rust, while still performing most tasks via commands.
You can throw down a function like this to reduce the boilerplate for calling commands:
fn run(command: &str) { let status = Command::new("sh") .arg("-c") .arg(command) .status() .unwrap(); assert!(status.success()); }Then you can just write
run("echo 'hello world' > test.txt");to run your command.Defining
runis definitely the quick way to do it 👍 I’d love to have a proc macro that takes a bash like syntax e.gsomeCommand | readsStdin | processesStdIn > someFileand builds the necessary rust to use. xonsh does it using a superset of python, but I never really got into it.Wow, that’s exactly what I was looking for! Thanks dude.
How easily can you start parsing arguments and read env vars? Do people import clap and such to provide support for those sorts of needs?
I’d use clap, yeah. And env vars
std::env::var("MY_VAR")?You can of course start writing your own macro crate. I wouldn’t be surprised if someone already did write a proc macro crate that introduces its own syntax to make calling subprocesses easier. The shell is… your oyster 😜I can only imagine that macro crate being a nightmare to read and maintain given how macros are still insanely hard to debug last I heard (might be a few years ago now).
Check out @Ephera@lemmy.ml’s comment with existing libraries. Someone already did the work! 🎉
I’m so glad we have madlads in rust land xD Thanks for referring me to that!
proc macros can be called in tests and debugged. They aren’t that horrible, but can be tedious to work with. A good IDE makes it a lot easier though, that’s for sure.
In your own description you added a bunch of considerations, requirements of following specific practices, having specific knowledge, and a ton of environmental requirements.
For simple scripts or duck tape schedules all of that is fine. For anything else, I would be at least mindful if not skeptical of bash being a good tool for the job.
Bash is installed on all linux systems. I would not be very concerned about some dependencies like sqlite, if that is what you’re using. But very concerned about others, like jq, which is an additional tool and requirement where you or others will eventually struggle with diffuse dependencies or managing a managed environment.
Even if you query sqlite or whatever tool with the command line query tool, you have to be aware that getting a value like that into bash means you lose a lot of typing and structure information. That’s fine if you get only one or very few values. But I would have strong aversions when it goes beyond that.
You seem to be familiar with Bash syntax. But others may not be. It’s not a simple syntax to get into and intuitively understand without mistakes. There’s too many alternatives of if-ing and comparing values. It ends up as magic. In your example, if you read code, you may guess that
:-means fallback, but it’s not necessarily obvious. And certainly not other magic flags and operators.
As an anecdote, I guess the most complex thing I have done with Bash was scripting a deployment and starting test-runs onto a distributed system (and I think collecting results? I don’t remember). Bash was available and copying and starting processes via ssh was simple and robust enough. Notably, the scope and env requirements were very limited.
You seem to be familiar with Bash syntax. But others may not be.
If by this you mean that the Bash syntax for doing certain things is horrible and that it could be expressed more clearly in something else, then yes, I agree, otherwise I’m not sure this is a problem on the same level as others.
OP could pick any language and have the same problem. Except maybe Python, but even that strays into symbolic line noise once a project gets big enough.
Either way, comments can be helpful when strange constructs are used. There are comments in my own Bash scripts that say what a line is doing rather than just why precisely because of this.
But I think the main issue with Bash (and maybe other shells), is that it’s parsed and run line by line. There’s nothing like a full script syntax check before the script is run, which most other languages provide as a bare minimum.
As one other comment mentioned, unfamiliarity with a particular language isn’t restricted to just bash. I could say the same for someone who only dabbles in C being made to read through Python. What’s this
@decoratorthing? Or what’sf"Some string: {variable}"supposed to do, and how’s memory being allocated here? It’s a domain, and we aren’t expected to know every single domain out there.And your mention of losing typing and structure information is… ehh… somewhat of a weird argument. There are many cases where you don’t care about the contents of an output and only care about the process of spitting out that output being a success or failure, and that’s bread and butter in shell scripts. Need to move some files, either locally or over a network, bash is good for most cases. If you do need something just a teeny bit more, like whether some key string or pattern exists in the output, there’s grep. Need to do basic string replacements? sed or awk. Of course, all that depends on how familiar you or your teammates are with each of those tools. If nearly half the team are not, stop using bash right there and write it in something else the team’s familiar with, no questions there.
This is somewhat of an aside, but jq is actually pretty well-known and rather heavily relied upon at this point. Not to the point of say sqlite, but definitely more than, say, grep alternatives like ripgrep. I’ve seen it used quite often in deployment scripts, especially when interfaced with some system that replies with a json output, which seems like an increasingly common data format that’s available in shell scripting.
Yes, every unfamiliar language requires some learning. But I don’t think the bash syntax is particularly approachable.
I searched and picked the first result, but this seems to present what I mean pretty well https://unix.stackexchange.com/questions/248164/bash-if-syntax-confusion which doesn’t even include the alternative if parens https://stackoverflow.com/questions/12765340/difference-between-parentheses-and-brackets-in-bash-conditionals
I find other languages syntaxes much more approachable.
I also mentioned the magic variable expansion operators. https://www.gnu.org/software/bash/manual/html_node/Shell-Parameter-Expansion.html
Most other languages are more expressive.
At the level you’re describing it’s fine. Preferably use shellcheck and
set -euo pipefailto make it more normal.But once I have any of:
- nested control structures, or
- multiple functions, or
- have to think about handling anything else than simple strings that other programs manipulate (including thinking about bash arrays or IFS), or
- bash scoping,
- producing my own formatted logs at different log levels,
I’m on to Python or something else. It’s better to get off bash before you have to juggle complexity in it.
-e is great until there’s a command that you want to allow to fail in some scenario.
I know OP is talking about bash specifically but pipefail isn’t portable and I’m not always on a system with bash installed.
-e is great until there’s a command that you want to allow to fail in some scenario.
Yeah, I sometimes do
set +e do_stuff set -eIt’s sort of the bash equivalent of a
try { do_stuff() } catch { /* intentionally bare catch for any exception and error */ /* usually a noop, but you could try some stuff with if and $? */ }I know OP is talking about bash specifically but pipefail isn’t portable and I’m not always on a system with bash installed.
Yeah, I’m happy I don’t really have to deal with that. My worst-case is having to ship to some developer machines running macos which has bash from the stone ages, but I can still do stuff like rely on
[[rather than have to deal with[. I don’t have a particular fondness for usingbashas anything but a sort of config file (withexport SETTING1=...etc) and some light handling of other applications, but I have even less fondness for POSIXsh. At that point I’m liable to rewrite it in Python, or if that’s not availaible in a user-friendly manner either, build a small static binary.It’s nice to agree with someone on the Internet for once :)
Have a great day!
If you’re writing a lot of shell scripts and checking them with Shellcheck, and you’re still convinced that it’s totally safe… I tip my hat to you.
Set don’t forget set -E as well to exit on failed subshells.
Can I slap a decorator on a Bash function? I love my
(viatenacity, even if it’s a bit wordy).Wanna check if a variable’s set to something expected?
if [[ <test goes here> ]]; then <handle>; fiHey, you can’t just leave out “test goes here”. That’s worst part by a long shot.
The rest of the syntax, I will have to look up every time I try to write it, but at least I can mostly guess what it does when reading. The test syntax on the other hand is just impossible to read without looking it up.I also don’t actually know how to look that up for the double brackets, so that’s fun. For the single bracket, it took me years to learn that that’s actually a command and you can do
man [to view the documentation.To be fair, you don’t always have to use the
[[syntax. I know I don’t, e.g. if I’m just looking for a command that returns 1 or 0, which happens quite a bit if you get to usegrep.That said,
man testis my friend.But I’ve also gotten so used to using it that I remember
-zand-nby heart :PIf you need to use bash a lot just to learn 2 “keywords”, then it’s not a good language.
I have looked at bash scripts in the past, and even written some (small amount). I had to look up
-zand-nevery time. I’ve written a lot more python than bash, that’s for sure. But even if I don’t write python for a year, when needed I can just write an entire python script without minimal doc lookups. I just need to search if the function I want is part ofsyd,osorpath.The first time I want to do an
else ifmy IDE will mark it red and I’ll writeeliffrom then on, same thing if I try to use{}.If a bash script requires at least one array and one if statement, I can write the entire thing in python faster than I can search how to do those 2 things in bash.
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.
Certainly so. The same applies to any languages we choose, no?
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.
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?
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.
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.
Pretty much all languages are middleware, and most of the original code was shell/bash. All new employees in platform/devops want to immediately push their preferred language, they want java and rust environments. It’s a pretty safe bet if they insist on using a specific language; then they don’t know how awk or sed. Bash has all the tools you need, but good developers understand you write libraries for functionality that’s missing. Modern languages like Python have been widely adopted and has a friendlier onboarding and will save you time though.
Pretty much all languages are middleware, and most of the original code was shell/bash.
What? I genuinely do not know what you mean by this.
2 parts:
- All languages are middleware. Unless you write in assembly, whatever you write isn’t directly being executed, they are being run through a compiler and being translated from your “middle language” or into 0s and 1s the computer can understand. Middleware is code used in between libraries to duplicate their functionality.
https://azure.microsoft.com/en-us/resources/cloud-computing-dictionary/what-is-middleware/ - Most original code was written in shell. Most scripting is done in the cli or shell language and stored as a
script.shfile, containing instructions to execute tasks. Before python was invented you used the basic shell because nothing else existed yet
The first part is confusing what “middleware” means. Rather than “duplicating” functionality, it connects libraries (I’m guessing this is what you meant). But that has nothing to do with a language being compiled versus “directly executed”, because compilation doesn’t connect different services or libraries; it just transforms a higher-level description of execution into an executable binary. You could argue that an interpreter or managed runtime is a form of “middleware” between interpreted code and the operating system, but middleware typically doesn’t describe anything so critical to a piece of software that the software can’t run without it, so even that isn’t really a correct use of the term.
The second part is just…completely wrong. Lisp, Fortran, and other high-level languages predate terminal shells; C obviously predates the shell because most shells are written in C. “Most original code” is in an actual systems language like C.
(As a side note, Python wasn’t the first scripting language, and it didn’t become popular very quickly. Perl and Tcl preceded it; Lua, php, and R were invented later but grew in popularity much earlier.)
You are stuck on 100% accuracy and trying to actually stuff to death. The user asked if it’s possible to write an application in bash and the answer is an overwhelming duh. Most assembly languages are emulators and they all predate C.
In addition to not actually being correct, I don’t think the information you’ve provided is particularly helpful in answering OP’s question.
- All languages are middleware. Unless you write in assembly, whatever you write isn’t directly being executed, they are being run through a compiler and being translated from your “middle language” or into 0s and 1s the computer can understand. Middleware is code used in between libraries to duplicate their functionality.
I’ve only ever used bash.
