How can I minify JSON in a shell script?

I've been looking for a way to uglify some JSON while in my bash console. This help using it afterward in another command (for example, to pass json inline to httpie).

Giving:

{
    "foo": "lorem",
    "bar": "ipsum"
}

I want to obtain:

{"foo":"lorem","bar":"ipsum"}

_{See the pretty-print counterpart.}

Solution

TL;DR

no install

python -c 'import json, sys;json.dump(json.load(sys.stdin), sys.stdout)' < my.json

very fast (with jj)

jj -u < my.json

Perf benchmark

Here's the script, using hyperfine:

#!/usr/bin/env bash

tmp=$(mktemp json.XXX)
tmp_md=$(mktemp md.XXX)

trap "rm $tmp $tmp_md" EXIT

cat <<JSON > $tmp
{
    "foo": "lorem",
    "bar": "ipsum"
}
JSON
hyperfine \
    --export-markdown $tmp_md \
    --warmup 100 \
    "jj -u < $tmp" \
    "yq eval -j -I=0 < $tmp" \
    "xidel -s - -e '\$json' --printed-json-format=compact < $tmp" \
    "jq --compact-output < $tmp" \
    "python3 -c 'import json, sys;json.dump(json.load(sys.stdin), sys.stdout)' < $tmp" \
    "ruby -r json -e 'j JSON.parse \$stdin.read' < $tmp"

pbcopy < $tmp_md

The result on my mac — MacBook Air (M1, 2020), 8 GB:

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`jj -u < json.p72`	1.3 ± 0.2	0.9	2.7	1.00
`yq eval -j -I=0 < json.p72`	4.4 ± 0.4	3.8	7.8	3.37 ± 0.65
`xidel -s - -e '$json' --printed-json-format=compact < json.p72`	5.5 ± 0.3	5.0	6.5	4.19 ± 0.77
`python3 -c 'import json, sys;json.dump(json.load(sys.stdin), sys.stdout)' < json.p72`	14.0 ± 0.4	13.4	15.0	10.71 ± 1.89
`jq --compact-output < json.p72`	14.4 ± 2.0	13.2	33.6	11.02 ± 2.45
`ruby -r json -e 'j JSON.parse $stdin.read' < json.p72`	47.3 ± 0.6	46.1	48.5	36.10 ± 6.32

Result for a large JSON file (14k lines):

http https://france-geojson.gregoiredavid.fr/repo/regions.geojson | jj -p > $tmp

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`jj -u < json.wFY`	3.4 ± 0.7	2.7	12.2	1.00
`jq --compact-output < json.wFY`	35.1 ± 0.4	34.5	36.1	10.24 ± 2.23
`python3 -c 'import json, sys;json.dump(json.load(sys.stdin), sys.stdout)' < json.wFY`	47.4 ± 0.5	46.3	48.7	13.82 ± 3.01
`xidel -s - -e '$json' --printed-json-format=compact < json.wFY`	55.5 ± 1.2	54.7	63.5	16.17 ± 3.53
`ruby -r json -e 'j JSON.parse $stdin.read' < json.wFY`	94.9 ± 0.7	93.8	96.8	27.65 ± 6.02
`yq eval -j -I=0 < json.wFY`	3087.0 ± 26.6	3049.3	3126.8	899.63 ± 195.81

_{And here is the pretty print counterpart benchmark}