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    find . -maxdepth 1 -name '*.yaml' -print0 | xargs -r0 the_tool

>To say "you're holding it wrong" is just folly. Bash is worthy of the same treatment that "A Fractal of Bad Design" gave PHP, and it has no place in anything that wants to call itself engineering.

If you have a problem that involves "run a command with a list of parameters but not if the list is empty" and you don't immediately think of `xargs -r`, then consider that it's because you don't understand the tools, not because the tools are bad.

Also, how much code would it take to do the same thing in python?

Probably something along the line of

  Popen(["the_tool"] + list(Path().glob("*.yml")))

This is reasonable in general, though in this case, I think this will replicate the problem of the second Bash version, as the problem there is with the_tool requiring at least one argument.

While dethanatos's point about Bash's default behavior with a non-matching glob is on target, the remainder of the example demonstrates a problem in the_tool, which will need to be worked around regardless of how you invoke it.

> If you have a problem that involves "run a command with a list of parameters but not if the list is empty" and you don't immediately think of `xargs -r`, then consider that it's because you don't understand the tools, not because the tools are bad.

find has -exec, xargs isn't necessary.

`-exec` would run the command for each file separately, which isn't what the original problem wanted, and I didn't want to assume that it would be equivalent.

It runs them separately if you end the exec with ";", it appends as many as possible to the same command if you end it with "+"

Ah yes, I always forget about that.

Doesn’t xargs also die at too many files? Fact is, bash manages to have more footguns than goddamn C, which is telling something

>Doesn’t xargs also die at too many files?

No?

Bash is amazing at being expressive and allowing for a ton of common things sysadmins / Devops / power users need to do with just one or a few lines of code vs a “proper” language that might require libraries, compiling stuff, or just a ton more SLOC + time debugging. If you don’t know what a glob is going to match, try it first. Understand the semantics. If you need portability, do that too, but a ton of what I end up using bash for is along the lines of slicing up poorly formatted inconsistent lists and running tools against stuff, possibly in conjunction with args from those lists, and for that it’s amazing. Stuff like jq helps a lot, and tools like xmlstarlet before that were great too. I remember trying to rewrite a script that was getting long and AWKward in Python and getting pretty frustrated with how explicit and error-prone it was there. Sure, the result was probably more robust, but it came at the expense of an order of magnitude more dev / debugging time. That’s not always necessary; sometimes “good enough” is good enough, and usually bash is good enough.

I'll submit that that's a solution.

But it's like, I have to turn my head around and stop doing one thing (globs), and switch over to another thing (find, xargs). The language has baited me down one way of doing it, when I shouldn't be doing it that way. I'm well aware of xargs (but not the -r flag). I typically avoid xargs, as our code has to¹ work on macOS & Linux, and xargs is one of those utilities whose available options differ between the two for even simple use cases. (Such as here, for the "does it exec on no args?".)

But it still proves the point: the equivalent Python is just so much more straight-forward, easier to read, and not apt to shoot me at a moments notice, and doesn't have bugs. A reader only familiar with Python's syntax can read and understand Python, and can write Python that is correct. Not so with bash, you have to understand, "oh, no, globs will screw you here, you need this flag from this utility" — no, it's lunacy.

Like, I can go down the road you're suggesting (and in the past, I did) and keep learning the nooks and crannies and intricacies of bash, each one adding to the nightmare fuel that is my understanding of shell. I can keep tweaking the script around various failure modes, letting each line fail in prod 3 different ways. Or, I can just re-write it in Python, or Rust, or any other sane language and have it never fail again, for reasons that would also either apply to bash, or apply and have worse consequences than bash. (E.g., the Python would raise, bash would just plow on with it.)

Your response is exactly the same as my response before I saw the light on PHP, C, etc.: "you're holding it wrong". No, it's a bad tool that guiles the user into holding it wrong. There are better tools that are easier to hold.

¹b/c despite all work being done for Linux, devs get MBPs, b/c the company can't manage more than exactly 1 type of machine, for everyone.

> To say "you're holding it wrong" is just folly. Bash is worthy of the same treatment that "A Fractal of Bad Design" gave PHP, and it has no place in anything that wants to call itself engineering.

is this a cloud AMD64 opinion that ignores the 2 trillion devices which Gartner predicts will never run python?

I recently finished a ~600 lines ash script and the kids at work which just graduated complained that *"Y u no python?" For them it was difficult to understand because apparently I avoided cat/grep/dirname/basename/etc and used shell syntax wherever possible to avoid shelling out. (the thing I did would only run when system reaches a certain load)

Everyone forgot that the target hardware has only busybox (ash) and was massively resource constrained. My only options were to implement what I was doing as an eBPF, in C, or shell (ash). The shell script took 4 days (and was refactored/optimized several times within that period), the C (or eBPF) program would have taken ~10 days and the eBPF which is the best solution is unmaintainable once I leave the company.

from a performance perspective I take a bash script any time. Also python programs over time have a risk of eventually pulling in a dozen dependencies.

Judging by the reaction of the kids at work, what you did is already unmaintainable.

Plus, if you are running shell out of necessity on a constrained system, that doesn't mean shell deserves to be a programming language where there's actual choice.

> what you did is already unmaintainable.

how so? there is no python or perl or ruby etc on the target. what would have been a maintainable option other than /bin/sh ? C/C++ ?

> where there's actual choice.

again what choice? :) as I said there is no other solution than what I've given. the system literally doesn't have anything else regardless what "I think" it should support.

Anything is unmaintainable if the maintainers don't have the foundational skills.

In which case those people are not actually maintainers.

If the kids refuse to learn anything new (to them), they chose the wrong occupation.

How is bash performant? It is literally interpret by lines, and starting a whole process per if statements..

Guessing: Automatic parallelization in pipelines, just as long as there isn't a wall that has to consume all its input like "sort".

> How is bash performant?

Typically, time spent interpreting control flow in a bash script is dwarfed by time spent in the programs called by the script.

> It is literally interpret by lines

It's just splitting lines into words to build up commands. It's not compiling C++.

> starting a whole process per if statements..

In the common pattern `if command1; then command2; fi`, if command1 is a builtin (e.g., `test` or `[`), then bash does not create a subprocess.

Still doesn’t make it fast in any meaning of the word, which was my original criticism.

You asked how bash is performant. I responded with reasons its performance is good in many applications. Here”s one more: bash starts up faster than other interpreters (e.g., Python), and startup time can often be a significant factor in overall performance.

On the contrary, I am 100% open to suggestions that BASH sucks. (Personally, I would have picked the inadequacies of `set -e` as my favorite ... unfortunate aspect.) My objection was very narrow: this specific article does a poor job at saying why shell sucks, and a worse job still at presenting Python as a superior alternative. That's not to say that good reasons to use something else don't exist, and it's not even to say that Python can't be that alternative. (Your sibling comments suggesting xonsh and https://amoffat.github.io/sh/ paint a fairly compelling way to actually move to python without losing the advantages of shell, for instance.)

Personally, I never use bash for scripting. I use the system's scripting shell, Debian's Dash or NetBSD Ash. Rhetorical question: If Bash was great for shell scripting, why doesn't the OS project choose it for scripting. When I compile the OS kernel and userland, the project (NetBSD) uses shell scripts not Python. Not suggesting the shell is necessarily better but I am suggesting it works and people understand it.

There are many ways to run a command on every .yaml file in a directory. Personally I like using xtrace. Something like:

   echo cd the_directory > 1.sh
   echo "test -f *.yaml" >> 1.sh
   ls -1 *.yaml|sed 's/^/the_tool /' >> 1.sh
   chmod +x 1.sh
   less 1.sh
   sh -ex 1.sh

As mostly a day-to-day shell user who automates some things, I do not use Python. Never had an outage.

My preferred way under those conditions would be more along the lines of "see if a safe command fails, do the desired command if not", like:

  if ls *.yaml > /dev/null; then
    the_tool *.yaml
  fi

That only looks simple because we don't know what problem was being solved.

Is it really right to not process any files just because one of them just disappeared?

In general, situations like this suffer from race conditions and time-of-check/time-of-use problems.

> Is it really right to not process any files just because one of them just disappeared?

No idea what you mean here, the glob can expand to one or many.

> In general, situations like this suffer from race conditions and time-of-check/time-of-use problems.

I mean, that's a problem in every version presented so far, one that I don't think can be fixed externally without something extra like hardlinking to a new directory, because "the_tool" apparently can't handle missing files and they can go missing when "the_tool" starts up. That's why I didn't even bother.

This tool of yours can not cope with files not existing, and causes production outages? Yet somehow you manage to blame bash for this? The outcome would not have been different if systemd or python started your tool.

In fact, handling that types of errors is what bash is suitable for. "If file is readable, process it" is not an unusual construct. Please do take care however to avoid races if this directory is a spool directory that can be populated at any time, in which case it is useful that rename() is atomic, sometimes an additional working directory is required. Again, this is how the operating system is designed and nothing the shell can gloss over.

I have seen many problems from previously unknown race conditions when concurrency is increased. Scripts have to be kept composable and trivial to understand in order to guard against that.

To be honest, I would argue to remove any script that looks like the last example above. It is not clear what side effects of that bizarre array construct are useful to the system. Keep scripts as simple and readable as possible, a trivial truth perhaps, applicable to every language, but one that needs to be reiterated until the end of our profession.

> This failed, b/c bash can't represent an empty array!

It absolutely can, I have no idea where you’re getting this idea.

What happens if someone runs `the_tool this-file-does-not-exist.yaml` or the yaml file is removed by some other means before you get a chance to process it? Does your world also come tumbling down in these cases? If yes, please stop blaming Bash for it.

Didn't know "Fractal of Bad Design" even existed. I like aspects of PHP. Sorry.

This isn’t you are holding it wrong It is in the “do as I want not as I say” category