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Pure Sh Bible

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Re: Pure Sh Bible

#51

Post by throwawaaarrgh »

cduzz wrote: post #7

I have to take exception to some of this; it's "technically correct" but like much of shell, likely full of terrifying edge cases that are best avoided. For instance, using eval to have variables with variable names is madness. $ var="world" $ eval "hello_$var=value" $ eval printf '%s\n' "\$hello_$var" I suppose the fancy business with printf is flexing, but I suspect the majority of people scanning documents like th…

Actually, eval, much like global variables (which are maligned by "real programmers" everywhere) actually works fine for a janky shell script.

Also, don't use echo, use printf. echo has different semantics and potential footguns depending on the platform.

Re: Pure Sh Bible

#52

Post by throwawaaarrgh »

awaythrow98765 wrote: post #45

If you are at this level of required complexity as in those examples, you should use a proper programming language, not shell. Half those snippets fail with spaces in the wrong place, newlines, control characters, etc. I think all such shell "magic" should come with a huge disclaimer pointing the user at better alternatives such as perl or python. And all snippets should have the necessary caveats on horribly broken…

Using a more advanced language just because you find shell syntax to be wacky is like using a car to get groceries because you find panniers or a backpack to be wacky. It's the use case that matters; if you're 60 meters from the store, just use your bike, or walk.

There are plenty of cases in which Perl or Python will make things much more complicated than 5 lines of spooky-looking shell script. Sometimes a little mystical sorcery is what the doctor ordered.

Re: Pure Sh Bible

#53

Post by akraker »

sevg wrote: post #6
dorfwald wrote: post #5

Earlier quoted context omitted.

Creator of neofetch.

And kisslinux. He seems to have gone off the grid though? Seemingly no public GitHub activity since 2021.

Unfortunately, it seems that he has dropped off the grid. Didn't realize this until you mentioned it actually. It's really too bad. Not a lot is known about why, but more information can be found here: https://www.reddit.com/r/kisslinux/comments/lsbz8n/an_update...

Re: Pure Sh Bible

#54

Post by lamontcg »

What is everyone's current favorite one-liner for replacing a string in all files that match?

In other words alternative implementations of this:

    ruby -pi -e "gsub(/Net::HTTPServerException/, 'Net::HTTPClientException')" {lib,knife}/**/*.rb

Re: Pure Sh Bible

#55

Post by atomicnumber3 »

throwawaaarrgh wrote: post #52
awaythrow98765 wrote: post #45

If you are at this level of required complexity as in those examples, you should use a proper programming language, not shell. Half those snippets fail with spaces in the wrong place, newlines, control characters, etc. I think all such shell "magic" should come with a huge disclaimer pointing the user at better alternatives such as perl or python. And all snippets should have the necessary caveats on horribly broken…

Using a more advanced language just because you find shell syntax to be wacky is like using a car to get groceries because you find panniers or a backpack to be wacky. It's the use case that matters; if you're 60 meters from the store, just use your bike, or walk. There are plenty of cases in which Perl or Python will make things much more complicated than 5 lines of spooky-looking shell script. Sometimes a little my…

Shell is full of ridiculous footguns though. It's like saying if the store is only 60m away (across an Indiana Jones-tier trap gauntlet) then just walk there.

Remember that time bumblebee accidentally deleted everyone's /usr? Or that time steam deleted everyone's homedir? Both because of the easiest to avoid bash footguns - spaces and empty variables.

My hard and fast rule that I've never regretted is - if you use a bash if statement, consider python. If you're going to do a for loop, you must instead use python.

Typically as a side effect once the programmer is in python at my prompting, they find having such easy access to libraries suddenly lets them make the whole script more robust - proper argparsing is an immediate one that comes to mind.

Frequently the reticence I see from people, especially juniors, is that they're worried about people thinking "haha they have to pull an entire python into their image just to run this script" or "wow they're so newbie/young that they can't even write some shell". I reassure them: don't worry, there's a reason we used Perl even back then too.

Re: Pure Sh Bible

#56

Post by cutler »

The Holy Grail of POSIX-portable shell scripts is irrelevant these days. Just use bash which is the default on most *nix systems.

Re: Pure Sh Bible

#57

Post by teddyh »

tpoacher wrote: post #33

Regarding conditional expressions: I found something neat recently. The coreutils version of `test` doesn't have this, and when you use `test`, typically what you're using is the coreutils one. But if you use `builtin test` to force the bash builtin variant of `test`, this has a nice `-v` switch, which allows you to check if a variable is set. I found out about this recently when I had to use it in my bash argument p…

If you already assume bash, then you don’t need the “-v” option to the “test” builtin; just do

  if [ "${foo+some_string}" = "" ]; then
    echo "foo is unset"
  fi
or, in your case:

  if test "${2+x}" = "" # i.e. if $2 is not set

Re: Pure Sh Bible

#58

Post by cutler »

awaythrow98765 wrote: post #45

If you are at this level of required complexity as in those examples, you should use a proper programming language, not shell. Half those snippets fail with spaces in the wrong place, newlines, control characters, etc. I think all such shell "magic" should come with a huge disclaimer pointing the user at better alternatives such as perl or python. And all snippets should have the necessary caveats on horribly broken…

"perl or python". Don't forget Ruby.

Re: Pure Sh Bible

#59

Post by teddyh »

darkteflon wrote: post #50
rmm wrote: post #49

i dont know about anyone else. but since ChatGPT, my shell game is probably the one that is most levelled up. A lot of things i would either do manually because i had forgotten shell programming, or i would have done in a seperate pyenv with 2-3 packages i can get done in about 4 minutes.

Same. Shell and glue-scripts in Python. The activation energy required is now close to zero.

I hope I never have to be the one to read those scripts.

Re: Pure Sh Bible

#60

Post by cutler »

lamontcg wrote: post #54

What is everyone's current favorite one-liner for replacing a string in all files that match? In other words alternative implementations of this: ruby -pi -e "gsub(/Net::HTTPServerException/, 'Net::HTTPClientException')" {lib,knife}/**/*.rb

I think you need `ruby -i -ple` to handle newlines properly.
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