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Laurence MorganAbout 3 min


JSON Lines


The following description is taken from jsonlines.orgopen in new window:

JSON Lines is a convenient format for storing structured data that may be processed one record at a time. It works well with unix-style text processing tools and shell pipelines. It's a great format for log files. It's also a flexible format for passing messages between cooperating processes.


Example JSON lines documents taken from jsonlines.orgopen in new window

Tabulated data

["Name", "Session", "Score", "Completed"]
["Gilbert", "2013", 24, true]
["Alexa", "2013", 29, true]
["May", "2012B", 14, false]
["Deloise", "2012A", 19, true] 

This format is equatable to generic and csv.

Nested objects

{"name": "Gilbert", "wins": [["straight", "7♣"], ["one pair", "10♥"]]}
{"name": "Alexa", "wins": [["two pair", "4♠"], ["two pair", "9♠"]]}
{"name": "May", "wins": []}
{"name": "Deloise", "wins": [["three of a kind", "5♣"]]}


Concatenated JSON

Technically the jsonl Unmarshal() method supports Concatenated JSON, as described on Wikipediaopen in new window:

Concatenated JSON streaming allows the sender to simply write each JSON object into the stream with no delimiters. It relies on the receiver using a parser that can recognize and emit each JSON object as the terminating character is parsed. Concatenated JSON isn't a new format, it's simply a name for streaming multiple JSON objects without any delimiters.

The advantage of this format is that it can handle JSON objects that have been formatted with embedded newline characters, e.g., pretty-printed for human readability. For example, these two inputs are both valid and produce the same output:

Single line concatenated JSON


Multi-line concatenated JSON

  "some": "thing\n"
  "may": {
    "include": "nested",
    "objects": [

...however in Murex's case, only single line concatenated JSON files (example 1) are supported; and that is only supported to cover some edge cases when writing JSON lines and a new line character isn't included. The primary example might be when generating JSON lines from inside a for loop.

This is resolved in the new data-type parser jsonc (Concatenated JSON). See line below.

More information

This format is sometimes also referred to as LDJSON and NDJSON, as described on Wikipediaopen in new window.

Murex's json data-type document also describes some use cases for JSON lines.

Default Associations

  • Extension: json-lines
  • Extension: jsonl
  • Extension: jsonlines
  • Extension: ldjson
  • Extension: murex_history
  • Extension: ndjson
  • MIME: application/json-lines
  • MIME: application/jsonl
  • MIME: application/jsonlines
  • MIME: application/ldjson
  • MIME: application/ndjson
  • MIME: application/x-json-lines
  • MIME: application/x-jsonl
  • MIME: application/x-jsonlines
  • MIME: application/x-ldjson
  • MIME: application/x-ndjson
  • MIME: text/json-lines
  • MIME: text/jsonl
  • MIME: text/jsonlines
  • MIME: text/ldjson
  • MIME: text/ndjson
  • MIME: text/x-json-lines
  • MIME: text/x-jsonl
  • MIME: text/x-jsonlines
  • MIME: text/x-ldjson
  • MIME: text/x-ndjson

Supported Hooks

  • Marshal() Supported
  • ReadArray() Works with JSON arrays. Maps are converted into arrays
  • ReadArrayWithType() Works with JSON arrays. Maps are converted into arrays. Element data type is json
  • ReadIndex() Works against all properties in JSON
  • ReadMap() Not currently supported.
  • ReadNotIndex() Works against all properties in JSON
  • Unmarshal() Supported
  • WriteArray() Supported

See Also

  • * (generic): generic (primitive)
  • [[ Element ]]: Outputs an element from a nested structure
  • cast: Alters the data type of the previous function without altering it's output
  • csv: CSV files (and other character delimited tables)
  • foreach: Iterate through an array
  • format: Reformat one data-type into another data-type
  • hcl: HashiCorp Configuration Language (HCL)
  • json: JavaScript Object Notation (JSON)
  • jsonc: Concatenated JSON
  • open: Open a file with a preferred handler
  • pretty: Prettifies JSON to make it human readable
  • runtime: Returns runtime information on the internal state of Murex
  • toml: Tom's Obvious, Minimal Language (TOML)
  • yaml: YAML Ain't Markup Language (YAML)
  • index: Outputs an element from an array, map or table
  • mxjson: Murex-flavoured JSON (deprecated)

Read more about type hooks

This document was generated from builtins/types/jsonlines/jsonlines_doc.yamlopen in new window.

Last update:
Contributors: Laurence Morgan,Laurence Morgan,Laurence