How to get a formatted json string from a json object? - json

Question

I'm storing the output of cat ~/path/to/file/blah | jq tojson in a variable to be used later in a curl POST with JSON content. It works well, but it removes all line breaks. I understand line breaks are not supported in JSON, but I'd like them to be replaced with \n characters so when the data is used it isn't all one line.
Is there a way to do this?
Example:
{
"test": {
"name": "test",
"description": "blah"
},
"test2": {
"name": "test2",
"description": "blah2"
}
}
becomes
"{\"test\":{\"name\":\"test\",\"description\":\"blah\"},\"test2\":{\"name\":\"test2\",\"description\":\"blah2\"}}"
but I'd like it to look like
{\n \"test\": {\n \"name\": \"test\",\n \"description\": \"blah\"\n },\n \"test2\": {\n \"name\": \"test2\",\n \"description\": \"blah2\" \n }\n}
I'm actually only converting it to a JSON string so it is able to be posted as part of another JSON. When is it posted, I'd like it to have the format it had originally which can be achieved if there are \n characters.
I can do this manually by doing
cat file | sed -E ':a;N;$!ba;s/\r{0,1}\n/\\n/g' | sed 's/\"/\\"/g')
but this is not ideal.

Answer 1

tojson (or other json outputting filters) will not format the json. It will take on the usual compact form. There is a feature request out there for this so look out for that in a future version.
You could take advantage of jq's regular formatted output, but you'll want to stringify it. You could simulate stringifying by slurping in as raw input, the formatted output. This will read in all of the input as a single string. And since the input was just a json object, it'll produce a string representation of that object.
If you don't mind the extra jq calls, you could do this:
$ var=$(jq '.' input.json | jq -sR '.')
$ echo "$var"
"{\n \"test\": {\n \"name\": \"test\",\n \"description\": \"blah\"\n },\n \"test2\": {\n \"name\": \"test2\",\n \"description\": \"blah2\"\n }\n}\n"
Then of course if your input is already formatted, you could leave out the first jq call.

Answer 2

If your input contains only one JSON value, then jq isn't really buying you much here: all you need is to escape the few characters that are valid in JSON but that don't represent themselves in JSON strings, and you can easily do that using command-line utilities for general-purpose string processing.
For example:
perl -wpe '
s/\\/\\<backslash>/g;
s/\t/\\t/g;
s/\n/\\n/g;
s/\r/\\r/g;
s/"/\\"/g;
s/\\<backslash>/\\\\/g
' ~/path/to/file/blah