Grep for a name-value pair inside a JSON object - json

Question

Have a shell script running on Unix that is going through a list of JSON objects like the following, collecting values like <init>() # JSONInputData.java:82. There are also other objects with other values that I need to retrieve.
Is there a better option than grepping for "STACKTRACE_LINE",\n\s*.* and then splitting up that result?
inb4: "add X package to the OS". Need to run generically.
. . .
"probableStartLocationView" : {
"lines" : [ {
"fragments" : [ {
"type" : "STACKTRACE_LINE",
"value" : "<init>() # JSONInputData.java:82"
} ],
"text" : "<init>() # JSONInputData.java:82"
} ],
"nested" : false
},
. . . .
What if I was looking for "description" : "Dangerous Data Received" in a series of objects like the following knowing that I need to know that it is associated with event 12345 and not with another event listed in the same file?
. . .
"events" : [ {
"id" : "12345",
"important" : true,
"type" : "Creation",
"description" : "Dangerous Data Received",
. . .

Answer 1

Is there a better option than grepping for "STACKTRACE_LINE",\n\s*.* and then splitting up that result?
Yes. Use jq to filter and extract the interesting parts.
Example 1, given this JSON:
{
"probableStartLocationView": {
"lines": [
{
"fragments": [
{
"type": "STACKTRACE_LINE",
"value": "<init>() # JSONInputData.java:82"
}
],
"text": "<init>() # JSONInputData.java:82"
}
],
"nested": false
}
}
Extract value where type is "STACKTRACE_LINE":
jq -r '.probableStartLocationView.lines[] | .fragments[] | select(.type == "STACKTRACE_LINE") | .value' file.json
This is going to produce one line per value.
Example 2, given this JSON:
{
"events": [
{
"id": "12345",
"important": true,
"type": "Creation",
"description": "Dangerous Data Received"
}
]
}
Extract the id where description starts with "Dangerous":
jq -r '.events[] | select(.description | startswith("Dangerous")) | .id'
And so on.
See the jq manual for more examples and capabilities.
Also there are many questions on Stack Overflow using jq,
that should help you find the right combination of filtering and extracting the relevant parts.