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 EagleEnglish
    2•5 hours 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.