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 pipefail is the short form of the following three commands:
      • set -e: exit on the first command that fails, rather than plowing through ignoring all errors
      • set -u: treat references to undefined variables as errors
      • set -o pipefail: If a command piped into another command fails, treat that as an error
    • export LC_ALL=C tells other programs to not do weird things depending on locale. For example, it forces seq to 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.

  • Eager Eagle@lemmy.worldEnglish
    3·
    3 days ago

    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.

    • esa@discuss.tchncs.de
      2·
      2 days ago

      Yeah, while -e has 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.)