1JSON(3am) GNU Awk Extension Modules JSON(3am)
2
6 json - import from and export to JSON format
7
9 @load "json"
10 status = json_fromJSON(string, array)
12 encoded = json_toJSON(array [, use_real_array])
14
16 JSON objects represent associations of names with values, what we will
17 call linear arrays (arrays with numeric indices), and subgroupings
18 (nested associative arrays). Such objects map well onto gawk's true
19 multidimensional associative arrays. This extension provides a mecha‐
20 nism to encode a gawk array as a JSON string and to decode a JSON
21 object into a gawk array.
22 The json extension adds two functions as follows:
24 json_fromJSON(string, array)
26 This function takes a string representing a JSON object and
27 decodes it into the array argument. The array is cleared first.
28 The return status is one upon success or zero upon failure. In
29 addition, gawk's ERRNO variable is updated to (sort of) indicate
30 what the problem was.
31 json_toJSON(array[, use_real_array])
33 This function takes an array argument and encodes the array con‐
34 tents as a JSON object in the returned string. The returned
35 string will be empty if an error of some kind occurred. In
36 addition, gawk's ERRNO variable is updated to (sort of) indicate
37 what the problem was.
38 If the optional parameter use_real_array is not zero, json_toJ‐
40 SON() encodes arrays indexed from 1 to N as JSON linear arrays,
41 instead of as associative arrays. This gives a better rendition
42 into JSON, at the expense of some additional CPU time to verify
43 that the array is indeed indexed linearly.
44
46 The mapping between gawk objects and JSON objects isn't perfect. In
47 particular, JSON boolean objects map to 1 or 0, losing the type dis‐
48 tinction. Typed regular expression constants in gawk are encoded as a
49 string, with the regexp bracketed by @/ and /. For example, pat‐
50 tern:"@/[a-z]+[0-9]?/".
51
53 @load "filefuncs"
54 @load "json"
55 ...
56 BEGIN {
57 stat("/etc/passwd", data)
58 statinfo = json_toJSON(data)
59 print statinfo
60 }
61 BEGIN {
63 getline statinfo
64 if (! json_fromJSON(statinfo, data))
65 print "JSON import failed!" > "/dev/stderr"
66 exit 1
67 }
68 # do something with the info
70 }
71
73 This extension uses RapidJSON to parse a JSON document into a gawk
74 array. This approximates the Document Object Model (DOM) paradigm. In
75 the author's humble opinion, the SAX paradigm for parsing JSON does not
76 match well with awk's design. If you want SAX parsing of JSON, this
77 isn't the place.
78
80 JSON home page: https://www.json.org/
81 Wikipedia: https://en.wikipedia.org/wiki/JSON
83 RapidJSON home page: http://rapidjson.org/
85
87 Arnold D. Robbins
88
90 Copyright © 2017, the Free Software Foundation, Inc.
91 Copyright © 2017, Arnold David Robbins.
92 Permission is granted to make and distribute verbatim copies of this
94 manual page provided the copyright notice and this permission notice
95 are preserved on all copies.
96 Permission is granted to copy and distribute modified versions of this
98 manual page under the conditions for verbatim copying, provided that
99 the entire resulting derived work is distributed under the terms of a
100 permission notice identical to this one.
101 Permission is granted to copy and distribute translations of this man‐
103 ual page into another language, under the above conditions for modified
104 versions, except that this permission notice may be stated in a trans‐
105 lation approved by the Foundation.
106Free Software Foundation Nov 22 2017 JSON(3am)