Question 285781 in Json Question posted in
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Can I just extract and output EventId from json file using jq in bash?

My json file is as follows. This is a sample file.

{
    "DocumentIncarnation":  1,
    "Events":  [
               ]
}

{
    "DocumentIncarnation":  2,
    "Events":  [
                   {
                       "EventId":  "C7061BAC-AFDC-4513-B24B-AA5F13A16123",
                       "EventStatus":  "Scheduled",
                       "EventType":  "Freeze",
                       "ResourceType":  "VirtualMachine",
                       "Resources":  [
                                         "WestNO_0",
                                         "WestNO_1"
                                     ],
                       "NotBefore":  "Mon, 11 Apr 2022 22:26:58 GMT",
                       "Description":  "Virtual machine is being paused because of a memory-preserving Live Migration operation.",
                       "EventSource":  "Platform",
                       "DurationInSeconds":  5
                   }
               ]
}

{
    "DocumentIncarnation":  3,
    "Events":  [
                   {
                       "EventId":  "C7061BAC-AFDC-4513-B24B-AA5F13A16123",
                       "EventStatus":  "Started",
                       "EventType":  "Freeze",
                       "ResourceType":  "VirtualMachine",
                       "Resources":  [
                                         "WestNO_0",
                                         "WestNO_1"
                                     ],
                       "NotBefore":  "",
                       "Description":  "Virtual machine is being paused because of a memory-preserving Live Migration operation.",
                       "EventSource":  "Platform",
                       "DurationInSeconds":  5
                   }
               ]
}

{
    "DocumentIncarnation":  4,
    "Events":  [
               ]
}

I want to output only EventId in the json file above.
What I tried is as follows, but I failed.

cat test.json | jq -c '.[] | [.EventId]'
jq: error (at <stdin>:5): Cannot index number with string "EventId"
jq: error (at <stdin>:25): Cannot index number with string "EventId"
jq: error (at <stdin>:45): Cannot index number with string "EventId"
jq: error (at <stdin>:51): Cannot index number with string "EventId"

I am deeply grateful to anyone who helps me. I’d appreciate it if you could help me grow one step further.

Tags:

2

Answers


  1. 0

    Your input is a stream of objects which you can address directly. Just iterate over the items of the .Events array, and extract the .EventId:

    jq -r '.Events[].EventId' test.json

    C7061BAC-AFDC-4513-B24B-AA5F13A16123
C7061BAC-AFDC-4513-B24B-AA5F13A16123

    Demo

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  2. 0

    You need to adjust the jq expression to extract only "EventId" from the JSON file. Since your JSON structure includes an array under "Events," you should use the following command:

    cat test.json | jq -c '.Events[] | .EventId'

    This command will iterate through each element in the "Events" array and extract the "EventId" from each element. The output will be a list of "EventId" values.

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