John Siu Blog

Tech - Business Tool, Personal Toys

JQ - Json Parser

☰ Table of Content

Cheat sheet for simple usage.

simple.json

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{
  "id":"01234567",
  "active":true,
  "name":{
    "first":"John",
    "last":"Siu"
  },
  "address": [
    "address line 1",
    "address line 2",
    "address line 3"
  ]
}

Command

CommandUsage
jq '.' simple.jsonPrint pretty
jq '.id' simple.jsonPrint value of id
jq -r '.id' simple.jsonPrint value of id, without quote
jq '.id, .active' simple.jsonPrint value of id and active
jq '.name.last' simple.jsonPrint value of last in name
jq '.address[0]' simple.jsonPrint first item of array address

Wildcard Select

jq don’t have wildcard select as of v1.6. So following does not work:

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journalctl -o json |jq -r '.| select(.SYSLOG_IDENTIFIER=="postfix*") | .SYSLOG_IDENTIFIER'

Workaround with select(|contains()) or select(|startswith()).

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journalctl -o json |jq -r '.| select(.SYSLOG_IDENTIFIER | contains("postfix")) | .SYSLOG_IDENTIFIER'
journalctl -o json |jq -r '.| select(.SYSLOG_IDENTIFIER | startswith("postfix")) | .SYSLOG_IDENTIFIER'

John Siu

Update: 2020-08-12
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