Jq Usage: Difference between revisions
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jq: error (at <stdin>:1): Cannot iterate over string ("blah") | jq: error (at <stdin>:1): Cannot iterate over string ("blah") | ||
=Array-to-Iterator Filter []= | ==Array-to-Iterator Filter []== | ||
The filter expects and array and produces an the array's elements as an ''iteration''. |
Revision as of 18:58, 1 March 2019
Internal
Command Line Options
-r
Output raw strings, not JSON content.
Universal Filters
Identity Filter .
Map Filters
Object Identifier-Index Filter .key
.key
The filter expects a map and produces the value associated with the key given as argument of the filter, or null if there is no such object. The value, if exists, can be a primitive, a map or an array.
cat example.json | jq '.color'
This syntax only works for "identifier-like" keys: keys that are all made of alphanumeric characters and underscore, and which do not start with a digit.
The .key syntax is actually an alias for the more generic syntax:
.["key"]
If the key contains special characters, the .key alias cannot be used, and the complete .["key"] syntax should be used:
jq '.["complex::key"]'
For:
{
"complex::color": "something"
}
jq '.complex::color'
will fail:
jq: error: syntax error, unexpected ':', expecting $end (Unix shell quoting issues?) at <top-level>, line 1: .complex::color
while
jq '.["complex::color"]'
will work.
Array Filters
Array Index Filter .[index]
.[zero-based-index]
selects the corresponding array element, or null if the index does not designate an element that exists.
For:
[
"blue",
"red",
"green"
]
jq '.[0]'
return "blue"
while
jq '.[5]'
returns null.
If the input is not an array, the filter fails:
echo \"blah\" | jq '.[]' jq: error (at <stdin>:1): Cannot iterate over string ("blah")
Array-to-Iterator Filter []
The filter expects and array and produces an the array's elements as an iteration.