Provided by: jo_1.9-1_amd64 
NAME
jo - JSON output from a shell
SYNOPSIS
jo [-p] [-a] [-B] [-D] [-e] [-n] [-v] [-V] [-d keydelim] [-f file] [–] [ [-s|-n|-b] word
...]
DESCRIPTION
jo creates a JSON string on stdout from words given it as arguments or read from stdin.
If -f is specified, jo first loads the contents of file as a JSON object or array, then
modifies it with subsequent words before printing the final JSON string to stdout. file
may be specified as - to read from jo’s standard input; this takes precedence over reading
words 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.
A missing or empty value normally results in an element whose value is null. If -n is
specified, this element is not created.
jo normally treats key as a literal string value. If the -d option is specified, key will
be interpreted as an object path, whose individual components are separated by the first
character of keydelim.
jo normally treats value as a literal string value, unless it begins with one of the
following characters:
value action
─────────────────────────────────────────
@file substitute the contents of file
as-is
%file substitute the contents of file
in base64-encoded form
:file interpret the contents of file
as JSON, and substitute the
result
Escape the special character with a backslash to prevent this interpretation.
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.
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. The file may be
specified as - to read from jo’s standard input.
TYPE COERCION
jo’s type guesses can be overridden on a per-word basis by prefixing word with -s for
string, -n for number, or -b for boolean. The list of words 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
}
}
The same example, using object paths:
$ jo -p -d. name=Jane point[]=1 point[]=2 geo.lat=10 geo.lon=20
{
"name": "Jane",
"point": [
1,
2
],
"geo": {
"lat": 10,
"lon": 20
}
}
Without -d, a different object is generated:
$ jo -p name=Jane point[]=1 point[]=2 geo.lat=10 geo.lon=20
{
"name": "Jane",
"point": [
1,
2
],
"geo.lat": 10,
"geo.lon": 20
}
Create empty objects or arrays, intentionally or potentially:
$ jo < /dev/null
{}
$ MY_ARRAY=(a=1 b=2)
$ jo -a "${MY_ARRAY[@]}" < /dev/null
["a=1","b=2"]
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 and if it starts with : the contents are
interpreted as JSON:
$ jo program=jo authors=@AUTHORS
{"program":"jo","authors":"Jan-Piet Mens <jpmens@gmail.com>"}
$ jo filename=AUTHORS content=%AUTHORS
{"filename":"AUTHORS","content":"SmFuLVBpZXQgTWVucyA8anBtZW5zQGdtYWlsLmNvbT4K"}
$ jo nested=:nested.json
{"nested":{"field1":123,"field2":"abc"}}
These characters can be escaped to avoid interpretation:
$ jo name="JP Mens" twitter='\@jpmens'
{"name":"JP Mens","twitter":"@jpmens"}
$ jo char=" " URIescape=\\%20
{"char":" ","URIescape":"%20"}
$ jo action="split window" vimcmd="\:split"
{"action":"split window","vimcmd":":split"}
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" ....
$ ls *.c | jo -a > source.json; ls *.h | jo -a > headers.json
$ jo -a :source.json :headers.json
[["base64.c","jo.c","json.c"],["base64.h","json.h"]]
Add elements to existing JSON:
$ jo -f source.json 1 | jo -f - 2 3
["base64.c","jo.c","json.c",1,2,3]
$ curl -s 'https://noembed.com/embed?url=https://www.youtube.com/watch?v=dQw4w9WgXcQ' | jo -f - status=Rickrolled
{ ...., "type":"video","author_url":"https://www.youtube.com/user/RickAstleyVEVO","status":"Rickrolled"}
Deduplicate object keys (jo appends duplicate object keys by default):
$ jo a=1 b=2 a=3
{"a":1,"b":2,"a":3}
$ jo -D a=1 b=2 a=3
{"a":3,"b":2}
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 respectively, and “null” as null. Disable with this option.
-D Deduplicate object keys.
-e Ignore empty stdin (i.e. don’t produce a diagnostic error when stdin is empty)
-n Do not add keys with empty values.
-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 value, 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 contains 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>