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A shell colon does nothing. Use it anyway

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Re: A shell colon does nothing. Use it anyway

#31

Post by nullsanity »

jghn wrote: post #15
AlecSchueler wrote: post #12

Earlier quoted context omitted.

Define "really good?" I don't think I've ever had them produce a script that I didn't need to correct in some way. They can write it, that's true, but we still need to be able to read it.

Fair. I'm comparing it to the output I see generated in more mainstream, day to day, languages. I'm not going to bother to get into an argument on if the frontier models can generate amazing code in general. What I've found is I can get get the frontier models to generate bash scripts, perl one liners, etc that do exactly what I need at roughly the same quality as any other code it generates.

[dead]

Re: A shell colon does nothing. Use it anyway

#32

Post by csydas »

genidoi wrote: post #24
zaptheimpaler wrote: post #4

life is way too short to deal with this nightmare of a language and its 50000 footguns for anything longer than a 2 line script, especially in the age of LLMs. Just write a python/TS/any real language script instead. Bash is great for the command line, it should be limited to use there.

I find LLM's too fall into the trap of writing a bash script for a task that clearly needs to be implemented in an Actual Language with Real Data Structures. For example, ask an LLM to bring up a SQL server with some schema + data preload step, and it will write a profoundly long bash script to do that task, every time.

my experience as well. claude produces functional but over-engineered scripts fairly frequently with often very questionably useful safety checks, especially for powershell.

a common tell of ai generated powershell is a script that has dedicated functions to check types, often via several methods, and happily prints the output of the checks to shell. i do not get why it does this but it often adds dozens of lines that really serve no purpose but to make the shell output look fancy

Re: A shell colon does nothing. Use it anyway

#33

Post by shric »

nomel wrote: post #28
jghn wrote: post #5

Earlier quoted context omitted.

It turns out that LLMs are really good at writing bash too. even perl! maybe we should rethink some of these lost bits because we no longer need to worry about the arcane parts.

Bash scripts requires "set -eu" at minimum, when written by LLM or human. It's the only language terrible enough to make the default behavior ignore undefined variables, commands, and execution errors, and happily continue executing whatever was produced by me smashing my hands on the keyboard, until the end of the file, while returning an exit code of 0, claiming complete success.

“Only language” eh? I only have a passing familiarity or very distant memory so could be wrong but I’d say these are the same:

Perl (needs use strict)

Ancient VB/VBA/VB script

Original PHP (no idea about modern)

PowerShell

Old Windows/DOS batch

Re: A shell colon does nothing. Use it anyway

#34

Post by refp »

kazinator wrote: post #25

> ( : The subshell execution parentheses and the colon are superfluous here, just: Redirections do not require a colon command to hang off of, and there is no need to fork a subshell to execute such a command. > ( : >> result.json ) && echo YES # is result.json writable? As a go-to idiom for a writability test, it gives me pause. If the file didn't exist, we created a zero-length one. That might be okay if we are goi…

They are NOT superflous, and all you need to prove it is `zsh` (but there are others that follow suit in similar fashions):

  zsh% echo "hello world" > data
  
  zsh%
So, if you want something that "everyone can use" without going into details about the difference between commonly used shells.. you'd use the null-command.

---

and given that we use the null-command, it _WILL_ behave different with or without subshell.. and all you need is `bash --posix` to prove it:

    % cat subshell.sh
    #!/bin/bash --posix
    ( :
The output above is not truncated, `no-subshell.sh` will stop executing due to the broken read.

---

One should never trust things just because they are written, but that also applies to comments on HN. Originally when I read your message I actually thought I made a mistake, I was very close to writing an apology comment and adding a note to the blog post, but not close enough - I had to test it again.

I'm thankful for the watchful eyes and scrutiny when reading things online, that's good - keep it up, but your message is factually wrong - on so many levels.

Re: A shell colon does nothing. Use it anyway

#35

Post by lobofta »

flexagoon wrote: post #14
zaptheimpaler wrote: post #4

life is way too short to deal with this nightmare of a language and its 50000 footguns for anything longer than a 2 line script, especially in the age of LLMs. Just write a python/TS/any real language script instead. Bash is great for the command line, it should be limited to use there.

Just use Fish

Or better yet Nushell

Re: A shell colon does nothing. Use it anyway

#36

Post by akoboldfrying »

kevincox wrote: post #2

I am not a huge fan of most of these, but a few do seem useful. : "${1:?missing argument, aborting!}" I wouldn't use this because I would want to give $1 a name for the rest of the script, so I would assign. But it can be a nice way to give a clear error for missing required environment variables. Many of the others (like truncating files) are probably more clearly written with dedicated commands, but may come in use…

"Shortcuts" like :? that tie together two unrelated things (checking a variable for a condition, expanding the value of that variable) drive me up the wall. It makes expressing just one of the two things harder than expressing both, leading to contortions when you want just one, like this use of :.

Re: A shell colon does nothing. Use it anyway

#37

Post by [deleted] »

refp wrote: post #34
kazinator wrote: post #25

> ( : The subshell execution parentheses and the colon are superfluous here, just: Redirections do not require a colon command to hang off of, and there is no need to fork a subshell to execute such a command. > ( : >> result.json ) && echo YES # is result.json writable? As a go-to idiom for a writability test, it gives me pause. If the file didn't exist, we created a zero-length one. That might be okay if we are goi…

They are NOT superflous, and all you need to prove it is `zsh` (but there are others that follow suit in similar fashions): zsh% echo "hello world" > data zsh% So, if you want something that "everyone can use" without going into details about the difference between commonly used shells.. you'd use the null-command. --- and given that we use the null-command, it _WILL_ behave different with or without subshell.. and a…

[deleted]

Re: A shell colon does nothing. Use it anyway

#38

Post by [deleted] »

kazinator wrote: post #25

> ( : The subshell execution parentheses and the colon are superfluous here, just: Redirections do not require a colon command to hang off of, and there is no need to fork a subshell to execute such a command. > ( : >> result.json ) && echo YES # is result.json writable? As a go-to idiom for a writability test, it gives me pause. If the file didn't exist, we created a zero-length one. That might be okay if we are goi…

[deleted]

Re: A shell colon does nothing. Use it anyway

#39

Post by Gigachad »

jghn wrote: post #5
zaptheimpaler wrote: post #4

life is way too short to deal with this nightmare of a language and its 50000 footguns for anything longer than a 2 line script, especially in the age of LLMs. Just write a python/TS/any real language script instead. Bash is great for the command line, it should be limited to use there.

It turns out that LLMs are really good at writing bash too. even perl! maybe we should rethink some of these lost bits because we no longer need to worry about the arcane parts.

I have seen them write massively more complex bash scripts than any normal person would ever attempt, but the failure rate is absurdly high compared to when they write sane typed languages.

Re: A shell colon does nothing. Use it anyway

#40

Post by orphereus »

I really hate bash because of its unreadable syntax, and this does not help it in any way.

We have some large bash scripts in my company, ~10,000 LOC spread across multiple files, all sourcing each other and what not. It is truly hard to read bash, which means it is truly hard to maintain bash, which means that when the one person knowing the bash scripts in your company goes away, you're in for some "fun".

My point is, these quirks are not useful, except for some bash enthusiasts.

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