How to extract array from within json to a separate txt file

Question

I have a .json file that I need to extract the SliceTiming field from into a separate txt file. I cannot use jq. If I could, my command would be

jq .SliceTiming[] *.json

Here is the .json file

{
"EchoTime": 0.033,
"RepetitionTime": 0.75,
"EffectiveEchoSpacing": 0.0005,
"SliceTiming": [
    0.51,
    0,
    0.365,
    0.0725,
    0.4375,
    0.2175,
    0.5825,
    0.2925,
    0.6575,
    0.145,
    0.51,
    0,
    0.365,
    0.0725,
    0.4375,
    0.2175,
    0.5825,
    0.2925,
    0.6575,
    0.145,
    0.51,
    0,
    0.365,
    0.0725,
    0.4375,
    0.2175,
    0.5825,
    0.2925,
    0.6575,
    0.145,
    0.51,
    0,
    0.365,
    0.0725,
    0.4375,
    0.2175,
    0.5825,
    0.2925,
    0.6575,
    0.145,
    0.51,
    0,
    0.365,
    0.0725,
    0.4375,
    0.2175,
    0.5825,
    0.2925,
    0.6575,
    0.145,
    0.51,
    0,
    0.365,
    0.0725,
    0.4375,
    0.2175,
    0.5825,
    0.2925,
    0.6575,
    0.145   ],
"PhaseEncodingDirection": "j-"}

If you can't use proper tools like jq, any guarantees how the json file is formatted wrt. white space, line endings etc.? — dirkt
– dirkt, Commented Nov 26, 2018 at 17:53
python is allowed although I would prefer to use grep, sed, or awk if possible. — Noah
– Noah, Commented Nov 26, 2018 at 17:57
I am running on a server, which does not have jq installed and I can't install jq or anything else. — Noah
– Noah, Commented Nov 26, 2018 at 18:20

Community · Accepted Answer · 2020-06-11 14:16:50Z

2

Seeing as python is allowed. This would be my preferred solution.

I don't feel comfortable dealing with sed, grep, awk as I do not know edge cases about the data.

Print array with , to stdout

cat data.json | python -c "import sys, json; print json.load(sys.stdin)['SliceTiming']"

Note: This example uses python2.7, unlikely to work with python3.x

Just the values output. No `[]` no `,`:

Created slice_out.py as I couldn't find a nice way to do inline terminal

import sys, json
slice_data = json.load(sys.stdin)['SliceTiming']
for s in slice_data: print s

Ran with cat data.json | python slice_out.py

edited Jun 11, 2020 at 14:16

CommunityBot

1

answered Nov 26, 2018 at 18:00

Dean Coakley

1215 bronze badges

Great thank you! The output is another array in the format [ XX , XX , XX ,...,XX ]. I would like to get the output as each number on a separate line without commas. Is there a way to do this?

Noah
– Noah

2018-11-26 18:05:57 +00:00
Commented Nov 26, 2018 at 18:05
I've added another solution. Let me know if that works for you

Dean Coakley
– Dean Coakley

2018-11-26 18:59:29 +00:00
Commented Nov 26, 2018 at 18:59

Add a comment |

Kusalananda · Accepted Answer · 2018-11-26 18:06:39Z

1

Using Perl and the JSON module:

perl -MJSON -e 'print join("\n", @{decode_json(join("\n",<>))->{"SliceTiming"}})' <file.json

This outputs each number on a separate line without commas

answered Nov 26, 2018 at 18:06

Kusalananda♦

356k42 gold badges737 silver badges1.1k bronze badges

Thank you! I guess I can't use this because i get an error. Can't locate JSON.pm in @INC (@INC contains: /usr/local/lib64/perl5 /usr/local/share/perl5 /usr/lib64/perl5/vendor_perl /usr/share/perl5/vendor_perl /usr/lib64/perl5 /usr/share/perl5 .). BEGIN failed--compilation aborted.

Noah
– Noah

2018-11-26 18:10:10 +00:00
Commented Nov 26, 2018 at 18:10
@Noah I guess you just have to install the JSON Perl module. It should be available as a package on your Unix (just like jq).

Kusalananda
– Kusalananda ♦

2018-11-26 18:13:48 +00:00
Commented Nov 26, 2018 at 18:13

Add a comment |

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