Didn't realize at first that "pure" refers to features available in bash without calling out to external processes, when I would've thought purism in this context should refer to avoiding bashisms and writing portable (ksh, POSIX shell) scripts.

I understand your concerns about bash features and POSIX compatibility. The bash bible was written specifically to document the shell extensions bash implements.

My focus for the past few months has been writing a Linux distribution (and its package manager/tooling) in POSIX sh.

I've learned a lot of tricks and I'm very tempted to write a second "bible" with snippets that are supported in all POSIX shells.

(I created the bash bible).

You can add me to those interested in a pure POSIX shell bible. Whenever I'm about to write a moderately large script, I'm actively avoiding bashisms as they don't buy me much yet make my script unportable. But, given you've spent so much time on this subject, are there any bashisms that are truly essential and you don't want to live without?

I've started working on it here: https://github.com/dylanaraps/pure-sh-bible

> are there any bashisms that are truly essential and you don't want to live without?

The only thing I'd say I miss when writing POSIX `sh` is arrays.

I work around this by using 'set -- 1 2 3 4' to mimic an array using the argument list. The limitation here though is that you're limited to one "array" at a time.

The other alternative I make use of is to use "string lists" (list="1 2 3 4") with word splitting.

This can be made safe if the following is correct:

- Globbing is disabled.

- You control the input data and can safely make assumptions (no spaces or new lines in elements).

While it's something that'd be nice to have, there are ways to work around it.

EDIT: One more thing would be "${var:0:1}" to grab individual characters from strings (or ranges of characters from strings).