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json - JSON parser

Table Of Contents


package require Tcl 8.5 9
package require json ?1.3.5?

::json::json2dict txt
::json::many-json2dict txt ?max?


The json package provides a simple Tcl-only library for parsing the JSON data exchange format as specified in RFC 4627 There is some ambiguity in parsing JSON because JSON has type information that is not maintained by the Tcl conversion. The json package returns data as a Tcl dict. Either the dict package or Tcl 8.5 is required for use.



An example of a JSON array converted to Tcl. A JSON array is returned as a single item with multiple elements.

       "precision": "zip",
       "Latitude":  37.7668,
       "Longitude": -122.3959,
       "Address":   "",
       "City":      "SAN FRANCISCO",
       "State":     "CA",
       "Zip":       "94107",
       "Country":   "US"
       "precision": "zip",
       "Latitude":  37.371991,
       "Longitude": -122.026020,
       "Address":   "",
       "City":      "SUNNYVALE",
       "State":     "CA",
       "Zip":       "94085",
       "Country":   "US"
{Country US Latitude 37.7668 precision zip State CA City {SAN FRANCISCO} Address {} Zip 94107 Longitude -122.3959} {Country US Latitude 37.371991 precision zip State CA City SUNNYVALE Address {} Zip 94085 Longitude -122.026020}

An example of a JSON object converted to Tcl. A JSON object is returned as a multi-element list (a dict).

    "Image": {
        "Width":  800,
        "Height": 600,
        "Title":  "View from 15th Floor",
        "Thumbnail": {
            "Url":    "",
            "Height": 125,
            "Width":  "100"
        "IDs": [116, 943, 234, 38793]
Image {IDs {116 943 234 38793} Thumbnail {Width 100 Height 125 Url} Width 800 Height 600 Title {View from 15th Floor}}


To write json, instead of parsing it, see package json::write.

Bugs, Ideas, Feedback

This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category json of the Tcllib Trackers. Please also report any ideas for enhancements you may have for either package and/or documentation.

When proposing code changes, please provide unified diffs, i.e the output of diff -u.

Note further that attachments are strongly preferred over inlined patches. Attachments can be made by going to the Edit form of the ticket immediately after its creation, and then using the left-most button in the secondary navigation bar.


data exchange, exchange format, javascript, json


CGI programming


Copyright © 2006 ActiveState Software Inc.
Copyright © 2009 Thomas Maeder, Glue Software Engineering AG