This aligns with recent forum posts, but we could also quote all interpolated variables (both here and in future posts):

As you wish. It may help readability, though is semantically identical, AFAIK.

It is. Such a change would only be for consistency and readability.

The code in forum posts is not assumed to be running inside a script, and so doesn't have this download-with-deferred-cleanup behavior. But unfortunately, that means it also doesn't have verification that the archive exists. We could get that by adding a HEAD request both here and in future posts, e.g.

echo "Verifying archive is at $ZIP_URL..." 1>&2
curl -fLI --no-progress-meter "$ZIP_URL" -o- > /dev/null

echo "Generating SHA-256 checksum..." 1>&2
CHECKSUM=sha256:$(curl -fL "$ZIP_URL" -o- | shasum -a 256 | cut -d' ' -f1)

Or just keeping the data (currently ~10 MB) in a variable:

ZIP_DATA=$(curl -fL "$ZIP_URL" -o-)
CHECKSUM=sha256:$(printf '%s' "$ZIP_DATA" | shasum -a 256 | cut -d' ' -f1)

I'd prefer using the -f flag to have curl fail fast:

echo "Verifying ${ZIP_URL} presence and generating SHA-256 checksum..." 1>&2
CHECKSUM=sha256:$(curl -fL "$ZIP_URL" -o- | shasum -a 256 | cut -d' ' -f1)

As noted above, the code in forum posts is not assumed to be running inside a script—so pipefail may not be active or even available (our instructions don't require bash). For example, here's what I see when running in a clean shell:

$ CHECKSUM=sha256:$(curl -L 'https://example.invalid/' -o- | shasum -a 256 | cut -d' ' -f1)
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
curl: (6) Could not resolve host: example.invalid
$ echo "CHECKSUM: $CHECKSUM"
CHECKSUM: sha256:e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855

But I do like the idea of using -f, and have updated accordingly.

I'd prefer using the -f flag to have curl fail fast:

echo "Verifying ${ZIP_URL} presence and generating SHA-256 checksum..." 1>&2
CHECKSUM=sha256:$(curl -fL "$ZIP_URL" -o- | shasum -a 256 | cut -d' ' -f1)

As you wish. It may help readability, though is semantically identical, AFAIK.