Add new element to existing JSON array with jq

Question

I want to append an element to an array in a JSON file using the jq``add command, but it's not working.

report-2017-01-07.json file:

{      "report": "1.0",    "data": {         "date": "2010-01-07",       "messages": [            {               "date": "2010-01-07T19:58:42.949Z",             "xml": "xml_samplesheet_2017_01_07_run_09.xml",             "status": "OK",             "message": "metadata loaded into iRODS successfully"          },          {               "date": "2010-01-07T20:22:46.949Z",             "xml": "xml_samplesheet_2017_01_07_run_09.xml",             "status": "NOK",             "message": "metadata duplicated into iRODS"          },          {               "date": "2010-01-07T22:11:55.949Z",             "xml": "xml_samplesheet_2017_01_07_run_09.xml",             "status": "NOK",             "message": "metadata was not validated by XSD schema"          }       ]    } } 

I am using this command:

$ cat report-2017-01-07.json  | jq -s '.data.messages {"date": "2010-01-07T19:55:99.999Z", "xml": "xml_samplesheet_2017_01_07_run_09.xml", "status": "OKKK", "message": "metadata loaded into iRODS successfullyyyyy"}' jq: error: syntax error, unexpected '{', expecting $end (Unix shell quoting issues?) at <top-level>, line 1: .data.messages {"date": "2010-01-07T19:55:99.999Z", "xml": "xml_samplesheet_2017_01_07_run_09.xml", "status": "OKKK", "message": "metadata loaded into iRODS successfullyyyyy"}                jq: 1 compile error 

Here's how I want the output to look:

{     "report": "1.0",     "data": {         "date": "2010-01-07",         "messages": [{             "date": "2010-01-07T19:58:42.949Z",             "xml": "xml_samplesheet_2017_01_07_run_09.xml",             "status": "OK",             "message": "metadata loaded into iRODS successfully"         }, {             "date": "2010-01-07T20:22:46.949Z",             "xml": "xml_samplesheet_2017_01_07_run_09.xml",             "status": "NOK",             "message": "metadata duplicated into iRODS"         }, {             "date": "2010-01-07T22:11:55.949Z",             "xml": "xml_samplesheet_2017_01_07_run_09.xml",             "status": "NOK",             "message": "metadata was not validated by XSD schema"         }, {             "date": "2010-01-07T19:55:99.999Z",             "xml": "xml_samplesheet_2017_01_07_run_09.xml",             "status": "OKKKKKKK",             "message": "metadata loaded into iRODS successfullyyyyy"         }]     } } 

Answer 1

The |= .+ part in the filter adds a new element to the existing array. You can use jq with filter like:

jq '.data.messages[3] |= . + {"date": "2010-01-07T19:55:99.999Z", "xml": "xml_samplesheet_2017_01_07_run_09.xml", "status": "OKKK", "message": "metadata loaded into iRODS successfullyyyyy"}' inputJson 

To avoid using the hardcoded length value 3 and dynamically add a new element, use . | length which returns the length, which can be used as the next array index, i.e.,

jq '.data.messages[.data.messages| length] |= . + {"date": "2010-01-07T19:55:99.999Z", "xml": "xml_samplesheet_2017_01_07_run_09.xml", "status": "OKKK", "message": "metadata loaded into iRODS successfullyyyyy"}' inputJson 

(or) as per peak's suggestion in the comments, using the += operator alone

jq '.data.messages += [{"date": "2010-01-07T19:55:99.999Z", "xml": "xml_samplesheet_2017_01_07_run_09.xml", "status": "OKKK", "message": "metadata loaded into iRODS successfullyyyyy"}]' 

which produces the output you need:

{   "report": "1.0",   "data": {     "date": "2010-01-07",     "messages": [       {         "date": "2010-01-07T19:58:42.949Z",         "xml": "xml_samplesheet_2017_01_07_run_09.xml",         "status": "OK",         "message": "metadata loaded into iRODS successfully"       },       {         "date": "2010-01-07T20:22:46.949Z",         "xml": "xml_samplesheet_2017_01_07_run_09.xml",         "status": "NOK",         "message": "metadata duplicated into iRODS"       },       {         "date": "2010-01-07T22:11:55.949Z",         "xml": "xml_samplesheet_2017_01_07_run_09.xml",         "status": "NOK",         "message": "metadata was not validated by XSD schema"       },       {         "date": "2010-01-07T19:55:99.999Z",         "xml": "xml_samplesheet_2017_01_07_run_09.xml",         "status": "OKKK",         "message": "metadata loaded into iRODS successfullyyyyy"       }     ]   } } 

Use jq-play to dry-run your jq-filter and optimize any way you want.

Answer 2

Rather than using |=, consider using +=:

.data.messages += [{"date": "2010-01-07T19:55:99.999Z",    "xml": "xml_samplesheet_2017_01_07_run_09.xml",    "status": "OKKK", "message": "metadata loaded into iRODS successfullyyyyy"}] 

Prepend

On the other hand, if (as @NicHuang asked) you want to add the JSON object to the beginning of the array, you could use the pattern:

 .data.messages |= [ _ ] + .