Jq to replace text directly on file (like sed -i)

Question

I have a json file that needs to be updated on a certain condition.

Sample json

{    "Actions" : [       {          "value" : "1",          "properties" : {             "name" : "abc",             "age" : "2",             "other ": "test1"           }       },       {          "value" : "2",          "properties" : {             "name" : "def",             "age" : "3",             "other" : "test2"           }       }    ] } 

I am writing a script that makes use of Jq to match a value and update, as shown below

cat sample.json |  jq '.Actions[] | select (.properties.age == "3") .properties.other = "no-test"' 

Output (printed to terminal)

{   "value": "1",   "properties": {     "name": "abc",     "age": "2",     "other ": "test1"   } } {   "value": "2",   "properties": {     "name": "def",     "age": "3",     "other": "no-test"   } } 

While this command makes the needed change, it outputs the entire json on the terminal and does not make change to the file itself.

Please advise if there is an option to have jq make changes on the file directly (similar to sed -i).

Answer 1

This post addresses the question about the absence of the equivalent of sed's "-i" option, and in particular the situation described:

I have a bunch of files and writing each one to a separate file wouldn't be easy.

There are several options, at least if you are working in a Mac or Linux or similar environment. Their pros and cons are discussed at http://backreference.org/2011/01/29/in-place-editing-of-files/ so I'll focus on just three techniques:

One is simply to use "&&" along the lines of:

jq ... INPUT > INPUT.tmp && mv INPUT.tmp INPUT 

Another is to use the sponge utility (part of GNU moreutils):

jq ... INPUT | sponge INPUT 

The third option might be useful if it is advantageous to avoid updating a file if there are no changes to it. Here is a script which illustrates such a function:

#!/bin/bash  function maybeupdate {     local f="$1"     cmp -s "$f" "$f.tmp"     if [ $? = 0 ] ; then       /bin/rm $f.tmp     else       /bin/mv "$f.tmp" "$f"     fi }  for f do     jq . "$f" > "$f.tmp"     maybeupdate "$f" done 

Answer 2

instead of sponge :

cat <<< $(jq 'QUERY' sample.json) > sample.json