从JSON仅提取特定流程的一个字段

Question

Below is the Json I receive as Response from url.

{"flows":[{"version":"OF_13","cookie":"0","tableId":"0x0","packetCount":"24","byteCount":"4563","durationSeconds":"5747","priority":"0","idleTimeoutSec":"0","hardTimeoutSec":"0","flags":"0","match":{},"instructions":{"instruction_apply_actions":{"actions":"output=controller"}}},

{"version":"OF_13","cookie":"45036000240104713","tableId":"0x0","packetCount":"0","byteCount":"0","durationSeconds":"29","priority":"6","idleTimeoutSec":"0","hardTimeoutSec":"0","flags":"1","match":{"eth_type":"0x0x800","ipv4_src":"10.0.0.10","ipv4_dst":"10.0.0.12"},"instructions":{"none":"drop"}},

{"version":"OF_13","cookie":"45036000240104714","tableId":"0x0","packetCount":"0","byteCount":"0","durationSeconds":"3","priority":"7","idleTimeoutSec":"0","hardTimeoutSec":"0","flags":"1","match":{"eth_type":"0x0x800","ipv4_src":"10.0.0.10","ipv4_dst":"127.0.0.1"},"instructions":{"none":"drop"}},

{"version":"OF_13","cookie":"0","tableId":"0x1","packetCount":"0","byteCount":"0","durationSeconds":"5747","priority":"0","idleTimeoutSec":"0","hardTimeoutSec":"0","flags":"0","match":{},"instructions":{"instruction_apply_actions":{"actions":"output=controller"}}}]}

So, I have for example four flows and I want to extract only the field " byteCount " for a specific flow identify by the ipv4_src and ipv4_dst that i have to give it as input

How can I do this?

Answer 1

json_array := JSON.parse(json_string)
foreach (element in json_array.flows):
    if(element.match.hasProperty('ipv4_src') && element.match.hasProperty('ipv4_dst')):
        if(element.match.ipv4_src == myValue && element.match.ipv4_dst == otherValue):
            print element.byteCount ;

The above is a pseudo-code to find byteCount based on ipv4_src and ipv4_dst . Note that these two properties are within match property, which may or may not contain them. Hence, first check for their existence and then process.

Note: When formatted property, each element in the array is like

{  
     "version":"OF_13",
     "cookie":"45036000240104713",
     "tableId":"0x0",
     "packetCount":"0",
     "byteCount":"0",
     "durationSeconds":"29",
     "priority":"6",
     "idleTimeoutSec":"0",
     "hardTimeoutSec":"0",
     "flags":"1",
     "match":{  
        "eth_type":"0x0x800",
        "ipv4_src":"10.0.0.10",
        "ipv4_dst":"10.0.0.12"
     },
     "instructions":{  
        "none":"drop"
     }
}

Answer 2

Here's how to perform the selection and extraction task using the command-line tool jq :

First create a file, say "extract.jq", with these three lines:

.flows[]
| select(.match.ipv4_src == $src and .match.ipv4_dst == $dst)
| [$src, $dst, .byteCount]

Next, assuming the desired src and dst are 10.0.0.10 and 10.0.0.12 respectively, and that the input is in a file named input.json, run this command:

jq -c --arg src 10.0.0.10 --arg dst 10.0.0.12 -f extract.jq input.json

This would produce one line per match; in the case of your example, it would produce:

["10.0.0.10","10.0.0.12","0"]

If the JSON is coming from some command (such as curl), you can use a pipeline along the following lines:

curl ... | jq -c --arg src 10.0.0.10 --arg dst 10.0.0.12 -f extract.jq