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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

#61

Post by _bernd »

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.

> Bash scripts requires "set -eu" at minimum, when written by LLM or human.

No. It does not. Just write good scripts and catch errors and handle them. That's the same more less with every language. And bash can be written in a way that it is sane and readable and maintainable. Just because you have seen a lot of junk in the language does not make the language bad per se. Sure there are a lot of languages "features" which are more then questionable but I want to rise again the point that it has its place and can be used in a good way.

Re: A shell colon does nothing. Use it anyway

#62

Post by m2f2 »

I usually skip the get option builtin, and use : as...

while : ; do case "$1" in "") break;; -f|-foo) shift; whatever;; *) usage; exit 1;; esac done

For this... instead

  if something; then 
     true
  else
     echo ERROR
     exit 1
  fi
Using : would be too much here.

For anything else including json etc. I usually go to duckdb. Awesome support, single file install, readable, easy to maintain.

Powershell on Linux or Unix? Just another huge dependency if you manage 1000s of machines, and good luck finding a Linux gal/guy wanting or able to touch pwsh without chemical grade gloves.

Re: A shell colon does nothing. Use it anyway

#63

Post by genidoi »

csydas wrote: post #32
genidoi wrote: post #24

Earlier quoted context omitted.

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 tha…

It's frustrating when I catch it doing this because it's wasting tokens and time on what it reports as "one-off" scripts. Might add a requirement to never use shell scripting unless the task is truly a one liner.

Re: A shell colon does nothing. Use it anyway

#64

Post by [deleted] »

delta_p_delta_x wrote: post #56
IdiotSavage wrote: post #51

What if there was a less cryptic way to have mandatory arguments, something harder to get wrong, like param( [parameter(mandatory)] $name ) "Hello, $name!" And then: $ ./script.ps1 Dave Hello, Dave! $ ./script.ps1 -name Dave Hello, Dave! $ ./script.ps1 cmdlet script.ps1 at command pipeline position 1 Supply values for the following parameters: name: Or non interactively: $ pwsh -nonint ./script.ps1 script.ps1: Cannot…

PowerShell needs to become more ubiquitous. There are so many things about it that once considered in greater detail make so much sense. Parameter setup, typing, and naming. Flow control. Object-oriented scripting. Built-in parsing for recursive data types like JSON, HTML, XML. And in my opinion, the most slept-on: the fact it runs on the CLR and direct access to .NET objects and types which means access to P/Invoke…

[deleted]

Re: A shell colon does nothing. Use it anyway

#65

Post by Affric »

PunchyHamster wrote: post #21

> Though.. what if I told you the above four lines could be replaced by just... one? I'd reject the pull request. Bash is already bad as programming language (the goodness of language for long code is inversely proportional to how nice it is for shell one-liners), this is just turning "bad" into "line noise" If your bash script takes more than one screen, rewrite it in Python, hell, rewrite it in Perl, even that's be…

Stupidly terse code is fun and a good laugh to show to people as a puzzle… it is the opposite in an application that relies on it.

Re: A shell colon does nothing. Use it anyway

#67

Post by crabbone »

IdiotSavage wrote: post #51

What if there was a less cryptic way to have mandatory arguments, something harder to get wrong, like param( [parameter(mandatory)] $name ) "Hello, $name!" And then: $ ./script.ps1 Dave Hello, Dave! $ ./script.ps1 -name Dave Hello, Dave! $ ./script.ps1 cmdlet script.ps1 at command pipeline position 1 Supply values for the following parameters: name: Or non interactively: $ pwsh -nonint ./script.ps1 script.ps1: Cannot…

PowerShell is a bad choice for the system shell because it's too complex. I'm not trying to justify all the quirks of Unix Shell, but minimalism is a very important feature of such a tool.

Another important feature of a tool like this is the ability to tolerate errors: I can't imagine a Linux today that would be able to even boot if the shell was extra pedantic about errors. A lot of mostly irrelevant things routinely fail on boot and during normal operation. Stamping them all out is an arduous... well, basically, an impossible task for practical purposes where releases are expected to come on time, where users may manipulate configuration in gazzilions of unpredictable ways.

PowerShell is just another language in the same box with Python, Perl, Ruby and many like that. It's not a good language, if you decided to reach for that box. Probably not the worst either.

System shell, however, isn't meant for writing entire applications. Writing applications with elaborate command-line interface should be left to languages that can properly address this problem. PowerShell is trying to be there, but it doesn't hold a candle to its "older brothers" who can, indeed, design a very robust command-line interface, often using a dedicated library for it.

PowerShell appeals to the novice crowd who are very enthusiastic about automatic checks in their code: the benefits are on the surface, the downsides are difficult to assess. This is in line with other Microsoft software products / languages which target novice programmers by implementing as many as possible of the highly-advertised features without regard to the overall usefulness of the product (think about C# or MS Office suit etc.)

Re: A shell colon does nothing. Use it anyway

#68

Post by valleyer »

_bernd wrote: post #61
nomel wrote: post #28

Earlier quoted context omitted.

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.

> Bash scripts requires "set -eu" at minimum, when written by LLM or human. No. It does not. Just write good scripts and catch errors and handle them. That's the same more less with every language. And bash can be written in a way that it is sane and readable and maintainable. Just because you have seen a lot of junk in the language does not make the language bad per se. Sure there are a lot of languages "features" w…

Ah yes, the Feynman Algorithm for shell scripting.

Re: A shell colon does nothing. Use it anyway

#69

Post by [deleted] »

refp wrote: post #6
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…

Yo, author here. You are very much correct and I 100% agree with you, I have updated the first example to include a snippet where a proper env-var is used to show of the automatic diagnostic. Thanks for your feedback, much much appreciated!

[deleted]

Re: A shell colon does nothing. Use it anyway

#70

Post by amiga386 »

Well that's exciting. I learned a lot of uses for ":" today.

However, the only one I already knew...

    if some-command; then
        :                            # command required
    else
        echo "command failed"
    fi
I used to do that until I learned of

    if ! some-command; then
        echo "command failed"
    fi
It's in the POSIX standard so it's not just a bashism: https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V...

> If the pipeline does not begin with the "!" reserved word, the exit status shall be the exit status of the last command specified in the pipeline. Otherwise, the exit status shall be the logical NOT of the exit status of the last command

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