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Comment by united893 | Hacker News Reader

This is generally terrible advice. A better option is to 'set -e' and ensure that the bash script exits when there's a failure.

Bash scripts can't be idempotent because they operate in an external environment that can't ever be. The better option is to just be extra safe.

See:

> http://redsymbol.net/articles/unofficial-bash-strict-mode/

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That's orthogonal to the article - in fact, the article hints that you'd take this advice when your bash script is failing midway, such as it might with `set -e`.

The article is about writing bash scripts that don't care if you've ran them once, or 10 times.

Precisely.

Op here. Exactly this. I’ve seen many times where people had scripts and had to modify it (such as commenting code) when something has failed in the middle of the script.

Don't forget about pipefail!!

set -eu set -o pipefail

Anything else I'm missing?

nounset

`set -x` can be very useful.

IIRC, `set -o nounset` is the bash equivalent for `set -u` in sh.

Seems like all the pedants came out for this article. In good-faith I understand the principles OP is suggesting and have first-hand experience of their usefulness. But it's easier to nit-pick I guess.

This is a case where the pedents should at least be considered.

Everytime I discuss Bash on the net, these gremlin style characters ruin the fruitful discussions I've had ... I think the article provides excellent advice.

>The article is about writing bash scripts that don't care if you've ran them once, or 10 times.

Is the idea that participants don't know what "idempotent" means in a thread with that word in the title?

I'm not sure why people see errors as a bad thing. Errors are good. They stop you from doing stupid things. But maybe this article is good for telling people why you should handle errors well or when you write code to make sure it fails gracefully. Because if you don't people are going to start telling others to use the force flag when removing (almost always a terrible idea).

Learn to handle errors, don't learn to brute force your way through them.

My understanding of 'set -e' is to ensure that errors are handled appropriately, not to brute force around them. If an error occurs that is not handled, this is treated as a problem and the script exits to ensure that one failure doesn't cause additional unforeseen problems as a result of the script running to completion.

The brute force method is the force flag (eg: `rm -f`). `set -e` is error handling. Force flag was constantly used in the post which is what I disagree with.

I agree. using -f is a poor excuse for not handling errors properly. imagine doing that in any other language.... oof

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