JSON - Jq Command line processor

by name

• produces the value at the properties key “foo”

jq .["foo$"] # The full qualified name
jq '.foo' # Short name

• or

.foo|.bar  (.foo.bar is equivalent)

• Optional (no error)

jq '.foo?'  

by key

Arrays are zero-based

.[1] # returns the second element.

• Slice 10 included, 15 excluded

.[10:15]

• No Error

.[]?

by Alias

• as - An Json object can be saved for later use with the as keyword in a pipe

jq '. as $alias | $alias '

Map (To Array)

Map(x) will run the input filter x for each element of the input array, and return the outputs in a new array

Example: The Map function returns the value of Json objects array in an array

[
    {"name":"JSON", "good":true}, 
    {"name":"XML", "good":false}
]

• Process

jq 'map(.name)' input.json

[
  "JSON",
  "XML"
]

To list

• Create a list

[
    {"name":"JSON", "good":true}, 
    {"name":"XML", "good":false}
]

• Process

jq '.[] | .name, .good' input.json

"JSON"
true
"XML"
false

Pipe

The | operator combines two filters by feeding the output(s) of the one on the left into the input of the one on the right.

[
    {"name":"JSON", "good":true}, 
    {"name":"XML", "good":false}
]

• Process

jq '.[] | .name' input.json

"JSON"
"XML"

Join (From Array to String)

From an array

[
  "1",
  "2"
]

join (",")

"1,2"

Without headers

[
    {"name":"JSON", "good":true}, 
    {"name":"XML", "good":false}
]

• Process (@csv need an array of an array as input)

jq -r '.[] | [.name, .good] | @csv' input.json

"JSON",true
"XML",false