All means are fair except solving the problem

https://yosefk.com/blog/all-means-are-fair-except-solving-the-problem.html

by akkartik • 3 months ago

83 56 3 months ago

PaulHoule4• 3 months ago

Aren't you supposed to return a 0 status code when "yea done!" and some other status code when it wasn't done?

yosefk• 3 months ago

Indeed you're supposed to, but that way if someone calls exit(0), it looks like the program worked fine, when in fact they committed some debug code and made the program no longer run to completion. "Yay, done" was put in for the scripts to flag this sort of thing, presumably based on experience.

PaulHoule4• 3 months ago

I can say up until 2005 or so I was a real believer in printf() debugging but I deliberately switched to using a debugger as much as possible around that time. I found that no matter how hard people "try" if they modifying the code to do debugging there is some chance these get checked in -- whereas you can investigate many things with the debugger without checking anything it.

Some applications have more trouble with setup and teardown than others. Like I knew a professor who kept sending me C programs that would crash before main() and some systems have a lot of trouble with "crash on shutdown" which might be a problem (corrupted files) or a non-problem.

kubb• 3 months ago

"People deliberately misuse the very mechanism that was designed to indicate successful completion, so we added another, flawed detection mechanism based on IO, because there's no way they'll do the thing that they should have learned in the first year of school, and just call exit with any other argument than 0 on irregular completion".

Gosh I thought the engineering culture was bad where I work.

anyfoo11• 3 months ago

Then that's utterly and horribly wrong? And in my decades of experience, I've fortunately only relatively rarely had to deal with that particular kind of atrocity.

atmavatar• 3 months ago

Next thing you know, you'll have to skip a major version number in your product because a significant fraction of your user base string parse its name to determine what version it is.

hiAndrewQuinn• 2 months ago

There is a parallel universe where the convention is that 0 is used for when something went wrong, and 1-127 are reserved for all the myriad and beautiful ways in which things went right.

sweetjuly• 2 months ago

As time goes on, I am beginning to wonder if sometimes the failure codes are good exits. Some tasks should not be done.

PaulHoule4• 2 months ago

Tolstoy: "All happy families are alike; each unhappy family is unhappy in its own way"

linkregister• 3 months ago

It's POSIX convention to write to stderr for anything that's not strict program output. I have seen 2>&1 far too often in scripts. I don't worry about it and happily write error messages to stderr whenever my scripts exit without a 0 status code.

ryandrake4• 3 months ago

Another thing that gets screwed up a lot is: Comand line usage help/information should be printed to stderr if it was invoked because the user passed an invalid option to the command line (in other words, the usage text counts as diagnostic[1] info), but it should be printed to stdout if the user invoked the application with -h, --help or similar. Reasons:

1. If you mess up the command line to the program in a script or pipe, and get a bunch of usage output in stdout, a downstream consumer of that stdout might think its legit program output and try to parse it.

2. If your user actually calls the program with -h or --help, they might want to |less through it to read it on a small terminal screen. Output that to stdout.

3. Generally, you can always tell if something is going wrong by grepping for errors or warnings a single stream (stderr), or by looking for a nonzero exit code.

But your general principle applies: Output expected by the user -> stdout. Diagnostic output or output incidental to the program's operation or errors -> stderr.

1: https://pubs.opengroup.org/onlinepubs/9799919799/functions/s...

anyfoo11• 3 months ago

Disagree. stdout is only reserved for actual processed command output. It may be empty, it may be invalid because the input was invalid (shit in, shit out), but it may never be things intended for a human to read.

If one wants to use a pager (like I sometimes do, though most of the time I just scroll up), they'll just use `foo 2>&1 | less`.

dylan6043• 2 months ago

3. Generally, you can always tell if something is going wrong by grepping for errors or warnings a single stream (stderr), or by looking for a nonzero exit code.

I'll use ffmpeg as an example of being an edge case. It's hard to get ffmpeg to give a nonzero exit code. What might be a problem for the user wasn't necessarily a problem for the app, so the app thinks it is completed and does its thing exiting with zero. For example, if a file is being read as input that is corrupted causing ffmpeg to no longer be able to read from the source, it will happily close your file cleanly so it is usable (just shorter than expected) and report it completed successfully. If all you do is check the exit code, you'll think your file is completed. Much more due diligence is necessary to be sure.

johnfn• 3 months ago

But the whole idea is that a warning is a warning. Solving a warning can be deferred, and a warning doesn't cause execution to fail. Your warning was transmuting itself into an error. I feel like "All means are fair except solving the problem" is the wrong conclusion to draw here. If it should have been solved immediately, it should have been an error in the first place. (And then you should have politely bumped the version so that you don't immediately break the code of all your dependents.) If there is no need to solve it immediately, then "all means are fair" to convert it back to a warning as was originally intended.

asdfasgasdgasdg• 3 months ago

The warning was only "transmuting" itself into an error because another team took a dependency in their test on the exact ordering of writes of certain data to a globally shared resource.

chadgpt2• 3 months ago

Was this FOSS or commercial?

If it's commercial software, you're paid to make it work, no matter how stupid that may be, and forced stupidity isn't your problem.

If it's FOSS, you can tell the user to deal with it and close the ticket.

debugnik• 2 months ago

The other team is also paid to make the whole thing work, though. That alone is not enough reason to yield.

potbelly832• 3 months ago

Why not have the program touch a file on success?

anyfoo11• 3 months ago

Why not have the program exit with exit code 0 on success, and non-0 on failure, like almost every program in a POSIX environment ever?

potbelly832• 3 months ago

see yosefk reply above

anyfoo11• 3 months ago

Does no one know what exit codes and stderr vs. stdout is anymore?

I work with old and new code bases used by many clients in complicated setups, but adding a warning to stderr while stdout was left untouched, and proper exit codes maintained, was hardly, if ever, a problem so far.

Of course, there's always some unpleasant exception, but it's rare.

And of course, I also understand that the author might have found themselves not only in one of those rare-ish instances, but also one where reasoning with the other side was fruitless.

adrian_b• 3 months ago

Yes, this was also exactly what I have thought while reading TFA.

AnimalMuppet• 3 months ago

I worked on a code base that ran on a variety of Unixes. One customer complained about file corruption from our software. Turns out that their Unix setup was... rather unique. Spawned programs were not given a stderr file handle! If you wrote to stderr, it scribbled on whatever file was open on file handle 2.

We, uh, reasoned with the other side - we told them to fix their stupid broken setup.

anyfoo11• 3 months ago

Glad you were able to sort it out properly. I guess maybe I'm also lucky to much less rarely work with, shall we say, consultation-resistant engineers than discussion forums sometimes make you believe.

dylan6043• 2 months ago

Does no one know what exit codes and stderr vs. stdout is anymore?

Sounds like you don't use ffmpeg very often. Because ffmpeg is able to send its output to stdout to be piped to other apps, verbose text output can't use stdout as one would expect. Non-error text is sent to stderr instead. So when you want to trap the text output you have to route stderr to text file. It takes some getting used to, but it's now normal for me.

So, yeah, I know stderr vs stdout still, but it's not what you want it to simply be. In the real world, things are not as clean as they are in school books.

skydhash• 2 months ago

I've just checked the man page for ffmpeg and they have a `-report` flag to capture the log. There should be no need to redirect stderr.

anyfoo11• 2 months ago

That is exactly what I expect, or did I misread you? I expect its text output on stderr, and stdout being reserved for its video (or whatever) output.

Maybe the name “stderr” is a bit misleading. It’s totally common for non-error output to be in stderr as well, like verbose/debug logging.

TheAdamist• 2 months ago

I always change my bash PS1 prompt to include the exit code of the previous command, makes experimenting to write scripts so much easier.

I also include the runtime of the previous command which is useful to find out how long commands take without having to remember to time each one.

anyfoo11• 2 months ago

Hah, I do the exact same. (Only in zsh.)

michaelt• 3 months ago

Instead, they were quick to point out that it’s hard to know where these warnings could come from, and we cannot risk all those critical workflows failing when some case of misuse surfaces in a new context.

Ah yes, Schroedinger's workflow. So important any disruption is a disaster, and simultaneously so unimportant they couldn't possibly spend a single dime on the tools critical to the workflow.

m463• 3 months ago

I have seen this kind of thing go so many ways.

- sometimes you can get the status code, sometimes you can't.

- sometimes you can separate out stdout from stderr, sometimes you can't

- sometimes the program generating the error message identifies itself, sometimes it doesn't

- sometimes you don't know if you have a "good error" (ok to ignore) or a "bad error" (cannot ignore)

I am a fan of the HARD FAIL.

I think internal unit tests or things like that should hard fail, then get a human to either fix it, or put in a hard exception.

if it is user-facing... sigh

shoo• 2 months ago

I am a fan of the HARD FAIL.

It reads as if the change was made to some library code that was depended upon by someone else's program that would "yay, done", which was in turn depended on by some workflow.

It's probably a non-starter to change library code so it hard fails if it detects its being used incorrectly, in situations where it previously ran and did something. That's a severe breaking change in behaviour.

Easing it in by printing a warning message sounds like a reasonable step toward hard failing. But then we get the situation yosefk relates.

chr15m• 3 months ago

Backwards compatibility is golden.

JanneVee• 2 months ago

We even have the options around in our compilers to treat warnings as errors. As continuation on that idea I for one was lucky earlier in my career to work with the brilliant idea of just asserting in production. Straight up crash the software when something was wrong. Wrong preconditions that could mess something in the future. "empty array where it isn't supposed to be empty, sorry crash - fix your bug". even when it kind of worked, which is the real issue... it kind of works until it doesn't. I've silently introduced this mindset into my work ever since and the quality of the result is so much better. Warnings are something that will be deferred when given the option so don't warn it is an error.

ninkendo• 2 months ago

One should always imagine a 1000:1 ratio of “person who reads a warning message” to “person who can do anything about it”.

You drop a little stderr print in your library saying “foo is deprecated, please use bar”, but then that library is included in another library which included in a CLI called by a script somewhere and, now the output goes to someone’s terminal when they’re running some management CLI. They never wrote the call to foo, they don’t even know what a foo is, they are 3 layers removed from who the target audience is.

Runtime is never the time to alert to things like deprecations or “this shouldn’t be used this way” notices. For deprecations, use your language’s built-in way of making functions deprecated. If your language doesn’t have that, use a real programming language. For other types of warnings, if you’re not 100% sure your message will only be seen by the developer who can fix it, just don’t write it.

moring• 2 months ago

Bonus points for the kafkaesque responses you get as the end-user when you try to actually pass that information upstream where it could be fixed...

All means are fair except solving the problem

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