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Comment by geocrasher | Hacker News Reader

I want to like this, but the for loop is unnecessarily messy, and not correct.

   for route in foo bar baz do
   curl localhost:8080/$route
   done

That's just begging go wonky. Should be

  stuff="foo bar baz"
  for route in $stuff; do
  echo curl localhost:8080/$route
  done

Some might say that it's not absolutely necessary to abstract the array into a variable and that's true, but it sure does make edits a lot easier. And, the original is missing a semicolon after the 'do'.

I think it's one reason I dislike lists like this- a newb might look at these and stuff them into their toolkit without really knowing why they don't work. It slows down learning. Plus, faulty tooling can be unnecessarily destructive.

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Even more correct would be to use an array:

  stuff=("foo foo" "bar" "baz")
  for route in "${stuff[@]}"; do
    curl localhost:8080/"$route"
  done

"${stuff[@]}" would be turning it back into "foo bar baz" though, right? I think if you were using arrays for this, it'd be something like:

    stuff=("foo" "bar" "baz");
    array_length=${#stuff[@]};
    for i in $(seq 0 $array_length); do
      curl localhost:8080/${stuff[i]}
    done

I'm betting even that isn't right: as soon as bash arrays are a thing, I reach for a different language.

[edit]: trying to get formatting correct

"${stuff[@]}" expands into the elements of the array, with each one quoted - so even that first "foo foo" element with a space will be handled correctly. That is how I would write the loop as well, in general.

However, your technique also works, with some tweaks:

* The loop goes one index too far, and can be fixed with seq 0 $(( array_length - 1 ))

* There should be quotes around ${stuff[i]} in case it has spaces

Oh, that's way better for sure! Thanks for the explanation

Yes that is more correct, I describe that here:

Thirteen Incorrect Ways and Two Awkward Ways to Use Arrays http://www.oilshell.org/blog/2016/11/06.html

In Oil the syntax is simplified to

    const stuff = %("foo foo" bar baz)
    for route in @stuff {
      curl localhost:8080/$route  # no quotes needed
    }

The bash syntax for arrays is obtuse and no one will spot when an error creeps in. It's worth to make an effort to say with space separated strings, as long as you are with bash. More advanced data structures is often an indication that it's worth glacing at something like python.

Should you need to handle spaces, it is often much easier to go with newline separated strings and use "| while read".

This contruction has the added benefit of the data not needing to fit in your environment. This can be a real issue, and is not at all obvious when it happens.

and on the off-chance that `stuff` must be a space-separated string for w/e reason:

  IFS=' ' read -ra routes <<<"${stuff}"
  for route in "${routes[@]}"; do
    curl localhost:8080/"$route"
  done

These are the types of stuff you typically run on the fly in the command line, not full blown scripts you intended to be reused and shared.

Here's a few examples from my command history:

  for ((i=0;i<49;i++)); do wget https://neocities.org/sitemap/sites-$i.xml.gz ; done

  for f in img*.png; do echo $f; convert $f -dither Riemersma -colors 12 -remap netscape: dit_$f; done

Hell if I know what they do now, they made sense when I ran them. If I need them again, I'll type them up again.

Seems like you could say the same thing about every snippet e.g. running jobs is the original purpose of a shell, (3) can be achieved using job specifications (%n), and using the `jobs` command for oversight.

Thanks for the note about the semicolon! Added it

Sure thing. I apologize if my comment came across as overly negative. My goal was constructive criticism, but based on the downvotes, I'm guessing I missed the mark there.

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