jq

A flexible and lightweight command line JSON processor

Supplementary instructions

jq is a lightweight and flexible command line JSON processor developed by stedolan. For the source code, please refer to jq project homepage

jq is used to process JSON input, apply a given filter to its JSON text input and generate the result of the filter as JSON on standard output.

The simplest filter is ., which copies jq's input to its output unmodified (except for formatting).

Note that jq currently only supports 64-bit double-precision floating point numbers (IEEE754).

Install

# Debian system, such as Ubuntu
sudo apt-get install jq

# RedHat system, such as CentOS
yum install jq

grammar

jq [options] <jq filter> [file...]
jq [options] --args <jq filter> [strings...]
jq [options] --jsonargs <jq filter> [JSON_TEXTS...]

Options

-c compact rather than pretty output;
-n Use `null` as a single input value;
-e sets the exit status code based on the output;
-s reads (sips) all input into an array; applies filter;
-r outputs raw strings instead of JSON text;
-R reads raw strings instead of JSON text;
-C Colorize JSON;
-M monochrome (do not color JSON);
-S sorts objects by key on output;
--tab Use tab characters for indentation;
--arg a v Set variable $a to value<v>;
--argjson a v Set variable $a to JSON value<v>;
--slurpfile a f Set variable $a to a JSON text array read from <f>;
--rawfile a f Set variable $a to a string containing the content of <f>;
--args The remaining arguments are string arguments, not files;
--jsonargs The remaining parameters are JSON parameters, not files;
-- Terminate parameter processing;

example

.: output in a pretty way

$ echo '{ "foo": { "bar": { "baz": 123 } } }' | jq '.'
{
   "foo": {
     "bar": {
       "baz": 123
     }
   }
}

.foo, .foo.bar, .foo?: Get the value of a key

$ echo '{"foo": 42, "bar": "less interesting data"}' | jq '.foo'
42

.[], .[]?, .[2], .[10:15]: Array operations

$ echo '[{"name":"JSON", "good":true}, {"name":"XML", "good":false}]' | jq '.[1]'
{
   "name": "XML",
   "good": false
}

[], {}: Construct an array/object

$ echo '{"user":"stedolan","titles":["JQ Primer", "More JQ"]}' | jq '{user, title: .titles[]}'

{
   "user": "stedolan",
   "title": "JQ Primer"
}
{
   "user": "stedolan",
   "title": "More JQ"
}

length: Calculate the length of a value

$ echo '[[1,2], "string", {"a":2}, null]' | jq '.[] | length'
2
6
1
0

keys: Remove the keys from the array

$ echo '{"abc": 1, "abcd": 2, "Foo": 3}' | jq 'keys'
[
   "Foo",
   "abc",
   "abcd"
]

,: use multiple filters

$ echo '{ "foo": 42, "bar": "something else", "baz": true}' | jq '.foo, .bar'
42
"something else"

|: Pipe the output of one filter as the input of the next filter

$ echo '[{"name":"JSON", "good":true}, {"name":"XML", "good":false}]' | jq '.[] | .name'
"JSON"
"XML"

select(foo): If foo returns true, the input remains unchanged

$ echo '[1,5,3,0,7]' | jq 'map(select(. >= 2))'
[
   5,
   3,
   7
]

map(foo): calls the filter for each input

$ echo '[1,2,3]' | jq 'map(.+1)'
[
   2,
   3,
   4
]

if-then-else-end: conditional judgment

  $ echo '2' | jq 'if . == 0 then "zero" elif . == 1 then "one" else "many" end'

"many"

\(foo): Insert values into strings and perform operations

$ echo '42' | jq '"The input was \(.), which is one less than \(.+1)"'

"The input was 42, which is one less than 43"