JQ

Person

JQ is short for Jamshed Qureshi.

Software

Description

jq is also a command-line tool for *nix and Windows for manipulating JSON data.

dbohdan 2015-01-29: You can use jq from Tcl, which can be faster than using Tcllib JSON when you only need a few values from a large JSON blob. It understands complex queries (called "filters") from .weather0.description to paths | map(tostring) | join("/") | unique to the one defined in the module below.

What follows is a small Tcl module to run jq that works in Tcl 8.5+ and Jim Tcl. Note that ::jq::json2dict is generally slower than ::json::json2dict (37 vs. 21 seconds to process a 10 MiB JSON file in Tcl 8.6.3). It is provided for the convenience of not having to import another package as well as for when you want

  1. your JSON arrays to be converted to dicts with integer keys (e.g., "a", "b", "c" to {0 a 1 b 2 c} rather than {a b c});
  2. a JSON parser in Jim Tcl faster than the recursive one from jimhttp.

The first point means that you can access data converted from JSON with dict get $jsonDict key1 0 key2 instead of having to alternate between dict get and lindex.

Download command

Download the module with wiki-reaper: wiki-reaper JQ 0 20 > jq-0.6.0.tm.

Module source code

# To use this module you need jq version 1.5rc1 or later installed.  However,
# jq 1.6 or later is highly recommended.  Due to a gsub() Unicode bug in earlier
# versions of jq (https://github.com/stedolan/jq/issues/1166), for example,
# fragments of CJK text in JSON may be missing or corrupted.

namespace eval jq {
    variable command jq
    variable version 0.6.0

    proc jq {filter data {options {-r}}} {
        variable command

        exec $command {*}$options $filter << $data
    }

    proc json2dict {data} {
        jq {
            def totcl:
                if type == "array" then
                    # Convert an array to an object with the keys 0, 1, 2, ...
                    # and process it as an object.
                    [
                        range(0; length) as $i
                        | {
                            key: $i | tostring,
                            value: .[$i]
                        }
                    ]
                    | from_entries
                    | totcl
                elif type == "object" then
                    .
                    | to_entries
                    | map("{\(.key | totcl)} {\(.value | totcl)}")
                    | join(" ")
                else
                    tostring
                    | gsub("{"; "\\{")
                    | gsub("}"; "\\}")
                end;
            . | totcl
        } $data
    }
}

dbohdan: I hope Jamshed doesn't mind me using this page. If he objects I will create a separate page for jq the program.