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My heart goes out to shell programmers who have to support posix sh (lemmy.world)
submitted 9 months ago by renzev@lemmy.world to c/linuxmemes@lemmy.world
92 comments fedilink hide all child comments

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.

(page 2) 45 comments
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[-] LordPassionFruit@lemm.ee 4 points 9 months ago

I have written 5 shell scripts ever, and only 1 of them has been more complex than "I want to alias this single command"

I can't imagine being an actual shell dev

[-] possiblylinux127@lemmy.zip 1 points 9 months ago

It really isn't bad especially if you use ash

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[-] jkercher@programming.dev 4 points 9 months ago

I was never a fan of set -e. I prefer to do my own error handling. But, I never understood why pipefail wasn't the default. A failure is a failure. I would like to know about it!

[-] owsei@programming.dev 3 points 9 months ago

IIRC if you pipe something do head it will stop reading after some lines and close the pipe, leading to a pipe fail even if everything works correctly

[-] jkercher@programming.dev 3 points 9 months ago

Yeah, I had a silly hack for that. I don't remember what it was. It's been 3-4 years since I wrote bash for a living. While not perfect, I still need to know if a pipeline command failed. Continuing a script after an invisible error, in many cases, could have been catastrophic.

[-] Integrate777@discuss.online 2 points 9 months ago

#!/usr/bin/python

[-] eager_eagle@lemmy.world 3 points 9 months ago* (last edited 9 months ago) 
#!/usr/bin/env python
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[-] Lightfire228@pawb.social 2 points 9 months ago* (last edited 9 months ago)

just use python instead.

  • wrap around subprocess.run(), to call to system utils
  • use pathlib.Path for file paths and reading/writing to files
  • use shutil.which() to resolve utilities from your Path env var

Here's an example of some python i use to launch vscode (and terminals, but that requires dbus)


from pathlib import Path
from shutil import which
from subprocess import run

def _run(cmds: list[str], cwd=None):
    p = run(cmds, cwd=cwd)

    # raises an error if return code is non-zero
    p.check_returncode()

    return p

VSCODE = which('code')
SUDO   = which('sudo')
DOCKER = which('docker')

proj_dir = Path('/path/to/repo')

docker_compose = proj_dir / 'docker/'

windows = [
  proj_dir / 'code',
  proj_dir / 'more_code',
  proj_dir / 'even_more_code/subfolder',
]
for w in windows:
  _run([VSCODE, w])

_run([SUDO, DOCKER, 'compose', 'up', '-d'], cwd=docker_compose)
[-] DieserTypMatthias@lemmy.ml 1 points 9 months ago

Or Rust. Use Command::new() for system commands and Path::new() for paths.

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this post was submitted on 15 Jan 2025
640 points (100.0% liked)

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