A commandline JSON processor powered by node.js.
Quick install and usage guide follow, find more info about jop in this blog post.
Install
Use npm to install jop globally:
npm install jop -g
and optionally to run the tests:
npm test
Tests depends on nodeunit.
Usage options
To test installation and display all available command options, invoke jop with -h:
→ jop -h
Usage: jop [OPTIONS] [JSON]
Process JSON in input executing an operation for each OPTION.
Many OPTIONS require a javascript expression that is evaluated on each item of the input
collection to perform the requested operation. In the expression context, current item
can be referenced via "it" and Lo-Dash javascript library via "_".
...
Options:
-c, --count Count all elements in input
--countby Count elements in input grouping by the given expression
-f, --findall Find all elements satisfying given expression
--find Find first element satisfying given expression
-g, --groupby Group input elements using given expression
--indexof Find index of the first element matching the given expression
--lastindexof Find index of the last element matching the given expression
--collect Collect the value of the given property name the input collection
--min Find the element having the max output for the given expression
--max Find the element having the min output for the given expression
--head Return the first n nodes, where n is a given number [default: 5]
-s, --sortby Sort input elements using the optionally provided expression
--sample Get n random elments from input, where n is a given number [default: 2]
-t, --transform Transform input node using the given expression, where "out" is the result object
--tail Return last n elements, where n is a given number [default: 5]
-p, --pretty Pretty-print output
--prop Return value for a given property name
--keys Collect object keys from input
--values Collect object values from input
-h, --help Display usage information
JSON content can be passed as input file or piped in from standard input (except on cygwin - cfr. Known issues).
Usage examples
Input files used in the following examples:
→ cat people.json
[{"name":"Andrea","age":19},{"name":"Beatrice", "age": 21},{"name":"Carlo", "age":16}]
→ cat simple.json
{
"type": "sample",
"link": "http://file-sample.com/json",
"name": "JavaScript Object Notation",
"metadata": [
{
"name": "extension",
"val": ".json"
},
{
"name": "media_type",
"val": "application/json"
},
{
"name": "website",
"val": "json.org"
}
]
}
Pretty-printing
Display input pretty-printed
→ jop -p people.json
[
{
"name": "Andrea",
"age": 19
},
{
"name": "Beatrice",
"age": 21
},
{
"name": "Carlo",
"age": 16
}
]
Filtering
Find items in a collection of objects
→ jop -f "it.age > 18" people.json
[{"name":"Andrea","age":19},{"name":"Beatrice", "age": 21}]
→ jop -f "it.age > 18" --collect "name" -f "it.indexOf("B") == 0" people.json
["Beatrice"]
→ jop --find "it.name.indexOf("a") > 0" people.json
{"name": "Andrea", "age": 19}
→ jop --indexof "it.age === 19" people.json
0
→ jop --lastindexof "it.age === 19" people.json
0
Extract a subset of objects from a collection
→ jop --head 1 people.json
[ {"name": "Andrea", "age": 19} ]
→ jop --tail 1 people.json
[{"name": "Carlo", "age": 16}]
→ jop --sample 2 people.json
[{name:"Carlo",age:16},{name:"Andrea",age:19}]
Get object having max/min property value (age value)
→ jop --max "it.age" people.json
{"name":"Beatrice", "age": 21}
→ jop --min "it.age" people.json
{"name":"Carlo", "age": 16}
Counting, grouping, sorting
Counting objects
→ jop --count people.json
3
→ jop --countby "it.age" people.json
{ "19": 1, "21": 1, "16": 1}
→ jop --countby "it.age > 18" people.json
{ true: 2, false: 1}
Grouping objects from a collection
→ jop --groupby "it.age" people.json
{ "19": 1, "21": 1, "16": 1}
→ jop --groupby "it.age > 18" people.json
{ true"19": 1, "21": 1, "16": 1}
Sorting objects in a collection
→ echo "[1,3,2]" | jop -s it
[1,2,3]
→ jop --sortby "it.age" people.json
[{name:"Carlo",age:16},{name:"Andrea",age:19},{name:"Beatrice",age:21}]
Extracting values
Collect property value (age value) for each object in the collection
→ jop --collect "age" people.json
[ 19, 21, 16 ]
Get the value of a property (eg. metadata property)
→ jop --prop "metadata" simple.json
[{name:"extension",val:".json"},{name:"media_type",val:"application/json"},{name:"website",val:"json.org"}]
Transformation
The transform option iterates over a collection binding, in the expression context, also:
outas the global result objectkeyas the current object key
So it is possible to tranform input into something else
(it, as usual, is the current object value).
Tranform input collection (create a person with name and year of birth)
→ jop -t "out[key] = { name: it.name, yob: new Date().getFullYear() - it.age }" -p people.json
[
{
"name": "Andrea",
"age": 19,
"yob": 1995
},
{
"name": "Beatrice",
"age": 21,
"yob": 1993
},
{
"name": "Carlo",
"age": 16,
"yob": 1998
}
]
Transform input adding a property (eg. year of birth) to each object
→ jop -t "out[key] = _.merge( _.mapValues(it), {yob: (new Date().getFullYear() - it.age)} )" -p people.json
[
{
"name": "Andrea",
"age": 19,
"yob": 1995
},
{
"name": "Beatrice",
"age": 21,
"yob": 1993
},
{
"name": "Carlo",
"age": 16,
"yob": 1998
}
]
The example above shows also how to use the _ variable to access Lo-Dash library methods in the expression context.
Known issues
No major issues at the moment. If you find one please let me know.