Provided by: jo_1.1-1_amd64 
NAME
jo - JSON output from a shell
SYNOPSIS
jo [-p] [-a] [-B] [-v] [-V] [--] [ [-s|-n|-b] word ...]
DESCRIPTION
jo creates a JSON string on stdout from _word_s given it as arguments or read from stdin. Without option
-a it generates an object whereby each word is a key=value (or key@value) pair with key being the JSON
object element and value its value. jo attempts to guess the type of value in order to create number
(using strtod(3)), string, or null values in JSON.
jo treats key@value specifically as boolean JSON elements: if the value begins with T, t, or the numeric
value is greater than zero, the result is true, else false. A missing or empty value behind the colon
results in a null JSON element.
jo creates an array instead of an object when -a is specified.
When the := operator is used in a word, the name to the right of := is a file containing JSON which is
parsed and assigned to the key left of the operator.
TYPE COERCION
jo's type guesses can be overridden on a per-word basis by prefixing word with -s for string, -n for num‐
ber, or -b for boolean. The list of _word_s must be prefixed with --, to indicate to jo that there are
no more global options.
Type coercion works as follows:
word -s -n -b default
─────────────────────────────────────────────────────────────────────
a= "a":"" "a":0 "a":false "a":null
a=string "a":"string" "a":6 "a":true "a":"string"
a="quoted" "a":""quoted"" "a":8 "a":true "a":""quoted""
a=12345 "a":"12345" "a":12345 "a":true "a":12345
a=true "a":"true" "a":1 "a":true "a":true
a=false "a":"false" "a":0 "a":false "a":false
a=null "a":"" "a":0 "a":false "a":null
Coercing a non-number string to number outputs the length of the string.
Coercing a non-boolean string to boolean outputs false if the string is empty, true otherwise.
Type coercion only applies to key=value words, and individual words in a -a array. Coercing other words
has no effect.
EXAMPLES
Create an object. Note how the incorrectly-formatted float value becomes a string:
$ jo tst=1457081292 lat=12.3456 cc=FR badfloat=3.14159.26 name="JP Mens" nada= coffee@T
{"tst":1457081292,"lat":12.3456,"cc":"FR","badfloat":"3.14159.26","name":"JP Mens","nada":null,"coffee":true}
Pretty-print an array with a list of files in the current directory:
$ jo -p -a *
[
"Makefile",
"README.md",
"jo.1",
"jo.c",
"jo.pandoc",
"json.c",
"json.h"
]
Create objects within objects; this works because if the first character of value is an open brace or a
bracket we attempt to decode the remainder as JSON. Beware spaces in strings ...
$ jo -p name=JP object=$(jo fruit=Orange hungry@0 point=$(jo x=10 y=20 list=$(jo -a 1 2 3 4 5)) number=17) sunday@0
{
"name": "JP",
"object": {
"fruit": "Orange",
"hungry": false,
"point": {
"x": 10,
"y": 20,
"list": [
1,
2,
3,
4,
5
]
},
"number": 17
},
"sunday": false
}
Booleans as strings or as boolean (pay particular attention to switch; the -B option disables the default
detection of the "true", "false", and "null" strings):
$ jo switch=true morning@0
{"switch":true,"morning":false}
$ jo -B switch=true morning@0
{"switch":"true","morning":false}
Elements (objects and arrays) can be nested. The following example nests an array called point and an
object named geo:
$ jo -p name=Jane point[]=1 point[]=2 geo[lat]=10 geo[lon]=20
{
"name": "Jane",
"point": [
1,
2
],
"geo": {
"lat": 10,
"lon": 20
}
}
Type coercion:
$ jo -p -- -s a=true b=true -s c=123 d=123 -b e="1" -b f="true" -n g="This is a test" -b h="This is a test"
{
"a": "true",
"b": true,
"c": "123",
"d": 123,
"e": true,
"f": true,
"g": 14,
"h": true
}
$ jo -a -- -s 123 -n "This is a test" -b C_Rocks 456
["123",14,true,456]
Read element values from files: a value which starts with @ is read in plain whereas if it begins with a
% it will be base64-encoded:
$ jo program=jo authors=@AUTHORS
{"program":"jo","authors":"Jan-Piet Mens <jpmens@gmail.com>"}
$ jo filename=AUTHORS content=%AUTHORS
{"filename":"AUTHORS","content":"SmFuLVBpZXQgTWVucyA8anBtZW5zQGdtYWlsLmNvbT4K"}
Read element values from a file in order to overcome ARG_MAX limits during object assignment:
$ ls | jo -a > child.json
$ jo files:=child.json
{"files":["AUTHORS","COPYING","ChangeLog" ....
OPTIONS
jo understands the following global options.
-a Interpret the list of words as array values and produce an array instead of an object.
-B By default jo interprets the strings "true" and "false" as boolean elements true and false respec‐
tively, and "null" as null. Disable with this option.
-p Pretty-print the JSON string on output instead of the terse one-line output it prints by default.
-v Show version and exit.
-V Show version as a JSON object and exit.
BUGS
Probably.
If a value given to jo expands to empty in the shell, then jo produces a null in object mode, and might
appear to hang in array mode; it is not hanging, rather it's reading stdin. This is not a bug.
Numeric values are converted to numbers which can produce undesired results. If you quote a numeric val‐
ue, jo will make it a string. Compare the following:
$ jo a=1.0
{"a":1}
$ jo a=\"1.0\"
{"a":"1.0"}
Omitting a closing bracket on a nested element causes a diagnostic message to print, but the output con‐
tains garbage anyway. This was designed thusly.
RETURN CODES
jo exits with a code 0 on success and non-zero on failure after indicating what caused the failure.
AVAILABILITY
<http://github.com/jpmens/jo>
CREDITS
• This program uses json.[ch], by Joseph A. Adams.
SEE ALSO
• <https://stedolan.github.io/jq/>
• <https://github.com/micha/jsawk>
• <https://github.com/jtopjian/jsed>
• strtod(3)
AUTHOR
Jan-Piet Mens <http://jpmens.net>
User Manuals JO(1)