jq select value from array

Question

I have the following JSON file with example values:

{
    "files": [{
        "fileName": "FOO",
        "md5": "blablabla"
    }, {
        "fileName": "BAR",
        "md5": "alaldlafj"
    }]
}

Now what I want is to return the md5 value where for example the fileName is "FOO". For this I have the following statement in jq:

cat <file>.json | jq '.[] | select(.fileName=="FOO")'

However response back is: jq: error (at <stdin>:11): Cannot index array with string "fileName"

What is the correct way to return the md5 value where the key fileName equals a certain argument?

score 80 · Accepted Answer · edited Aug 16 '23 at 22:35

80

Found the answer:

cat <file>.json | jq -r '.files[] | select(.fileName=="FOO") | .md5'

edited Aug 16 '23 at 22:35

Benjamin Loison

answered Jun 01 '16 at 11:11

Marvin Effing

20

Why bring `cat` into this? You can simply `jq -r '.files[] | select(.fileName=="FOO") | .md5' ` – Brent D. Jun 17 '21 at 00:03
8

@BrentD. - You are right that your version is shorter and simpler. However, some such as myself strongly prefer the strictly left-to-right structure that beginning with `cat` provides, especially when pipes are involved. – bitinerant Dec 07 '22 at 18:59
2

A shorter, simpler line that maintains strict left-to-right ordering is ` – Scott Centoni May 25 '23 at 07:12

score 12 · Answer 2 · answered Sep 30 '21 at 23:56

12

to answer the more generic how to select value from array selecting all filenames:

cat results.json | jq '.files[] | .filename'

answered Sep 30 '21 at 23:56

jmunsch

The question was about selecting a specific field based on value of other field. Not about selecting all the fields. – Mika Riekkinen Jun 08 '23 at 12:53

score 7 · Answer 3 · edited Aug 04 '20 at 10:24

7

or:

cat <file>.json | jq -r '.files[] | select(.fileName=="FOO").md5'

edited Aug 04 '20 at 10:24

Rob Paisley

answered Dec 03 '19 at 17:33

Alex Berger

9

Welcome to Stackoverflow! Please consider reading [this](https://stackoverflow.com/help/how-to-answer) section to improve your answer. Can you provide an explanation for the code you have posted here? – Kevin Dec 03 '19 at 18:35

3 Answers3