Json with ksh

[semaley]

I've been working a bit with moving back and forth between JSON (or yaml) text and associative arrays. Surely others have been seeing this, but most of the shell scripting shared online relies on jq, json.sh, etc. Then I saw David Korn commenting 12 years ago to look for it in the next alpha: https : ast-users research att narkive com /5dh0zrOt /json-with-ksh (sorry for broken link, but wasn't sure whether it'd trigger anything)

Next alpha will have a print -j and printf "%(json)B" to print a compound
shell variable in json format. I suspect the the other direction will
be a separate command.

Let me know if this works correctly after you get it.

David Korn
***@research.att.com

[McDutchie]

There is no harm in posting links here. I found the original thread.

Apparently the feature was quite broken in the alpha, and ksh2020 (which forked from the alpha, and is now also defunct) removed it. att#820

I'll try to backport it from the alpha to the 93u+m dev branch and see if I can fix it. It will take time.

[semaley]

I've been getting a surprising amount of mileage out of data structures, but there have been a number of core dumps hitting undefined chunks, and as the structures get larger (spreading to more -C/-A structures helps), so I wouldn't be surprised the integrated json ran into a mess. I really appreciate you taking a look.

This seems like a killer capability on top of a little known killer capability, which really makes a difference once explored. I have 100s of database instances moving from one datacenter to another, and this is part of comparing a "gold standard" across numerous potential downstream instances. The JSON seems to be a preferred way to communicate between components in our infrastructure, so configuration drift can be more visible.

In case any readers need it, picking values from simple JSON is pretty easy:
a string: ${JSON/#field_name~(E)"\s:\s*"?([^\"])./\1}
a number/true/false/null: ${JSON/#field_name~(E)"\s:\s*"?(true|false|null|\d*).*/\1}
...
I'm probably lacking imagination for the ksh regex, but the solutions online tend to subshell, sometimes several layers thick. The ksh function I came up with doing this, but into typeset -A/C was a little larger than expected. I suspect it would be a little easier in the C, and then saw that David Korn response on it.

[ormaaj]

I would very much prioritize working on the primitives necessary to support user-defined collections over bolting on a one-off json parser-serializer. Even though the work was done and it sort of demonstrated the principle. Yes the json thing was very broken.

[andychu]

BTW OSH is fairly ksh compatible, because it's bash compatible - https://oils.pub/

#886

And it has JSON, and the garbage-collected data structures necessary to represent JSON data. I posted a demo here recently:

https://news.ycombinator.com/item?id=44406885

---

OSH and YSH both have JSON built-in, and they have the hierarchical/recursive data structures you need for the common Python/JS-like API:

osh-0.33$ var d = { date: $(date --iso-8601) }

osh-0.33$ json write (d) | tee tmp.txt
{
  "date": "2025-06-28"
}

Parse, then pretty print the data structure you got:

$ cat tmp.txt | json read (&x)

osh-0.33$ = x
(Dict)  {date: '2025-06-28'}

Create a JSON syntax error on purpose:

osh-0.33$ sed 's/"/bad/"' tmp.txt | json read (&x)
sed: -e expression #1, char 9: unknown option to `s'
  sed 's/"/bad/"' tmp.txt | json read (&x)
                                 ^~~~
[ interactive ]:20: json read: Unexpected EOF while parsing JSON (line 1, offset 0-0: '')