Explanation for newbies:
-
Shell is the programming language that you use when you open a terminal on linux or mac os. Well, actually "shell" is a family of languages with many different implementations (bash, dash, ash, zsh, ksh, fish, ....)
-
Writing programs in shell (called "shell scripts") is a harrowing experience because the language is optimized for interactive use at a terminal, not writing extensive applications
-
The two lines in the meme change the shell's behavior to be slightly less headache-inducing for the programmer:
set -euo pipefailis the short form of the following three commands:set -e: exit on the first command that fails, rather than plowing through ignoring all errorsset -u: treat references to undefined variables as errorsset -o pipefail: If a command piped into another command fails, treat that as an error
export LC_ALL=Ctells other programs to not do weird things depending on locale. For example, it forcesseqto output numbers with a period as the decimal separator, even on systems where coma is the default decimal separator (russian, dutch, etc.).
-
The title text references "posix", which is a document that standardizes, among other things, what features a shell must have. Posix does not require a shell to implement
pipefail, so if you want your script to run on as many different platforms as possible, then you cannot use that feature.
After tens of thousands of bash lines written, I have to disagree. The article seems to argue against use of -e due to unpredictable behavior; while that might be true, I've found having it in my scripts is more helpful than not.
Bash is clunky. -euo pipefail is not a silver bullet but it does improve the reliability of most scripts. Expecting the writer to check the result of each command is both unrealistic and creates a lot of noise.
When using this error handling pattern, most lines aren't even for handling them, they're just there to bubble it up to the caller. That is a distraction when reading a piece of code, and a nuisense when writing it.
For the few times that I actually want to handle the error (not just pass it up), I'll do the "or" check. But if the script should just fail, -e will do just fine.
This is why I made the reference to Go. I honestly hate Go, I think exceptions are great and very ergonomic and I wish that language had not become so popular. However, a whole shitload of people apparently disagree, hence the popularity of Go and the acceptance of its (imo) terrible error handling. If developers don't have a problem with it in Go, I don't see why they'd have a problem with it in Bash. The error handling is identical to what I posted and the syntax is shockingly similar. You must unpack the return of a func in Go if you're going to assign, but you're totally free to just assign an err to
_in Go and be on your way, just like you can ignore errors in Bash. The objectively correct way to write Go is to handle everyerrthat gets returned to you, either by doing something, or passing it up the stack (and possibly wrapping it). It's a bunch of bubbling up. My scripts end up being that way too. It's messy, but I've found it to be an incredibly reliable strategy. Plus, it's really easy for me to grep for a log message and get the exact line where I encountered an issue.This is all just my opinion. I think this is one of those things where the best option is to just agree to disagree. I will admit that it irritates me to see blanket statements saying "your script is bad if you don't set -euo pipefail", but I'd be totally fine if more people made a measured recommendation like you did. I likely will never use set -e, but if it gets the bills paid for people then that's fine. I just think people need to be warned of the footguns.
EDIT: my autocorrect really wanted to fuck up this comment for some reason. Apologies if I have a dumb number of typos.
Yeah, while
-ehas a lot of limitations, it shouldn't be thrown out with the bathwater. The unofficial strict mode can still de-weird bash to an extent, and I'd rather drop bash altogether when they're insufficient, rather than try increasingly hard to work around bash's weirdness. (I.e. I'd throw out the bathwater, baby and the family that spawned it at that point.)