jq replace part of value in json

Question

I need to replace part of a value from a json output. I could easily do this using sed -i however it would also replace other parts of the file I don't want it to, unless I'm missing something. The output is

{
  "LastModified": "2018-03-07T17:24:33.000Z",
  "Key": "pending/archive/f7ab1684-e94d-483e-ace1-560367c1196c_1000_s.json"
}

and I need to replace the dash "-" on the LastModified value to a slash, then remove some stuff too like the "T" and the ".000Z" So I can eventually convert that timestamp to epoch.

I tried using cat list | jq -r '.[] | select (.LastModified == "-") .LastModified = "/"' and |= operator but I can't find anywhere else on the web that this has been accomplished.

score 20 · Accepted Answer · answered Mar 08 '18 at 20:55

20

With jq's sub() and fromdate() functions:

jq '.LastModified |= (sub("\\.000Z";"Z") | fromdate)' input.json

The output:

{
  "LastModified": 1520443473,
  "Key": "pending/archive/f7ab1684-e94d-483e-ace1-560367c1196c_1000_s.json"
}

answered Mar 08 '18 at 20:55

RomanPerekhrest

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Exactly what i was looking for and worked flawlessly. Can you explain everything thats going on? what does "Z" do? – Ryan Loeffler Mar 08 '18 at 21:07
Just realized, guessing here, that Z sets the time to UTC? – Ryan Loeffler Mar 08 '18 at 21:11
@RyanLoeffler, `Z` in datetime strings is universal time (UTC) designator https://en.wikipedia.org/w/index.php?title=ISO_8601 – RomanPerekhrest Mar 08 '18 at 21:18

score 4 · Answer 2 · answered Mar 08 '18 at 21:02

If your platform supports it, you could use the date functions to parse out then reformat the date string.

.LastModified |= (sub("\\.000Z$"; "Z") | fromdateiso8601 | strftime("%Y/%m/%d %H:%M:%S"))

Otherwise, you could use the usual string manipulation techniques.

.LastModified |= "\(.[:10] | sub("-"; "/"; "g")) \(.[11:19])"

Both results in the results:

{
  "LastModified": "2018/03/07 17:24:33",
  "Key": "pending/archive/f7ab1684-e94d-483e-ace1-560367c1196c_1000_s.json"
}

jq replace part of value in json

2 Answers2