Append JSON file after specific array index by using shell script - json

Question

I want to append some content by using shell script.
I have a JSON file test.json as below.
{
"reference": "Json Test",
"title": {
"a": "Json Test"
},
"components": [
{
"reference": "Json Test",
"type": "panel",
"content": [
{
"link": "abc/123",
"label": {
"a": "for test 123 - a",
"b": "for test 123 - b"
}
},
{
"link": "abc/456",
"label": {
"a": "for test 456 - a",
"b": "for test 456 - b"
}
},
{
"link": "abc/789",
"label": {
"a": "for test 789 - a",
"b": "for test 789 - b"
}
}
]
}
]
}
I want to append the content and output as following by using shell script (*.sh) How can I achieve this ?
{
"reference": "Json Test",
"title": {
"a": "Json Test"
},
"components": [
{
"reference": "Json Test",
"type": "panel",
"content": [
{
"link": "abc/123",
"label": {
"a": "for test 123 - a",
"b": "for test 123 - b"
}
},
{
"link": "abc/101112",
"label": {
"a": "for test 101112 - a",
"b": "for test 101112 - b"
}
},
{
"link": "abc/456",
"label": {
"a": "for test 456 - a",
"b": "for test 456 - b"
}
},
{
"link": "abc/789",
"label": {
"a": "for test 789 - a",
"b": "for test 789 - b"
}
}
]
}
]
}
I tried to access the index and add some test string, the below command will replace the original data.
jq '.components[].content[1] + { "link" : "test" } ' test.json

Answer 1

You can use the slice filter to extract the head and the tail of the array, then use + to concatenate head + the new object + the tail. Finally, use update-assignment |= to modify the array:
.components[].content |= .[0:1] + [{ link: "test" }] + .[1:]
If you are planning on using this more often, consider defining a reusable function:
def splice($at; $obj): .[0:$at] + [$obj] + .[$at:];
.components[].content |= splice(1; {link: "test"})

Answer 2

Grab the empty sub-array at position 1 (slicing either by start and end position .[1:1], or by start position and length .[1:][:0]), and assign to it your insert value formatted as (single-element) array [{"link": "test"}] (as you are assigning to an array after all - add more items to it if you want to add all of them at once). This looks almost like your original attempt:
jq '.components[].content[1:1] = [{"link": "test"}]' test.json
For convenience, you can also turn this into an insertAt function:
def insertAt($pos; $val): .[$pos:$pos] = [$val];
.components[].content |= insertAt(1; {"link": "test"})