Selection Path Syntax

Selection Path Syntax

To give a general idea, yajs selection path is heavly inspired on jsonpath while being a subset of it (i.e. not everything is supported).

• Root Object: Every yajs path starts with the $ root object reference, for instance:

Example: yajs '$'

$ echo '{ "prop1": "value1" }' | yajs '$'
{"prop1":"value1"}

• Path Separator: Property path selections are separated by a .:

Example: yajs '$.prop1.prop2'

$ echo '{ "prop1": { "prop2": "nested" } }' | yajs '$.prop1.prop2'
"nested"

• Array Values: The syntax does not changes for an array value so a . should be used to address the properties of the object values (in contrast with jsonpath syntax):

Example: yajs '$.prop1.prop2'

$ echo '{ "prop1": [ { "prop2": "nested1" }, { "prop2": "nested2" } ] }' | yajs '$.prop1.prop2'
"nested1"
"nested2"

Note: this also means that there is no way to address an specific index inside an array.

• Deep Nested Values: Deep nested values can be addressed using double . notation, without the need to specify the actual property path:

Example: yajs '$..prop3'

$ echo '{ "prop1": { "prop2": { "prop3": "nested" } } }' | yajs '$..prop3'
"nested"

• Path Filter Expression: A boolean expression can be combined with deep nested syntax so values will be selected only if it is addressed by a set o parent property keys that satisfies the boolean expression:

Example: yajs '$..[prop1 || prop2]prop3'

$ echo '[ { "prop1": { "prop3": "nested1" } }, { "prop2": { "prop3": "nested2" } }, { "skipped": { "prop3": "nested1" } } ]' | yajs '$..[prop1 || prop2]prop3'
"nested1"
"nested2"

• Property Filter Expression: A boolean expression can be combined with deep nested syntax so values will be selected only if the value is an object that contains a set of property keys that satisfies the boolean expression:

Example: yajs '$..prop1{nested1 || nested2}'

$ echo '[ { "prop1": { "nested1": "value1" } }, { "prop1": { "nested2": "value2" } }, { "skipped": { "nested3": "value3" } } ]' | yajs '$..prop1{nested1 || nested2}'
{"nested1":"value1"}
{"nested2":"value2"}

Note: this is only currently supported as being the last component of the yajs path.

• Wildcard: A wildcard * can be used to address values in which the property is unknown:

Example yajs '$.prop1.*'

$ echo '{ "prop1": [ { "prop2": "nested1" }, { "random": "nested2" }, { "unknown": "nested3" } ] }' | yajs '$.prop1.*'
"nested1"
"nested2"
"nested3"