How to get an ISO 8601 timestamp with milliseconds in BASH

BASH: ISO 8601 Timestamp with Milliseconds

Gist title: "BASH: ISO 8601 Timestamp with Milliseconds"

Summary: How to get an ISO 8601 timestamp with milliseconds in BASH

BASH ISO 8601 timestamp.md

For mac OS, the date utility doesn't give the right information. In that case, use homebrew to install the GNU date utility:

brew install coreutils

Homebrew will install the utility as gdate instead of date, which leaves the original date untouched and available.

gdate has an --iso-8601 option available, but it doesn't give a timestamp that strictly follows the ISO 8601 standard, as far as I can determine. I find it better to explicitly state the format with:

gdate -u +'%Y-%m-%dT%H:%M:%S.%3NZ'

Two things to not about the format string:

0. The 3 in %3N specifies that the fractional seconds (nanoseconds) should only be displayed to three decimal places (milliseconds).

typo: %Y-%m-%dT%H:%M:%S.%3NZ should be %Y-%m-%dT%H:%M:%S.%3N%Z (the Z needs to be %Z).

.. and I think for ISO8601 should be Z%Z .. ?

Thanks for this gist. It's a shame that the macOS version doesn't support finer granularity than seconds.