[javascript] Is there a way to 'pretty' print MongoDB shell output to a file?

Specifically, I want to print the results of a mongodb find() to a file. The JSON object is too large so I'm unable to view the entire object with the shell window size.

Also there is mongoexport for that, but I'm not sure since which version it is available.

Example:

mongoexport -d dbname -c collection --jsonArray --pretty --quiet --out output.json

Just put the commands you want to run into a file, then pass it to the shell along with the database name and redirect the output to a file. So, if your find command is in find.js and your database is foo, it would look like this:

./mongo foo find.js >> out.json

I managed to save result with writeFile() function.

> writeFile("/home/pahan/output.txt", tojson(db.myCollection.find().toArray()))

Mongo shell version was 4.0.9

you can use this command to acheive it:

mongo admin -u <userName> -p <password> --quiet --eval "cursor = rs.status(); printjson(cursor)" > output.json

Using this answer from Asya Kamsky, I wrote a one-line bat script for Windows. The line looks like this:

mongo --quiet %1 --eval "printjson(db.%2.find().toArray())" > output.json

Then one can run it:

exportToJson.bat DbName CollectionName

Put your query (e.g. db.someCollection.find().pretty()) to a javascript file, let's say query.js. Then run it in your operating system's shell using command:

mongo yourDb < query.js > outputFile

Query result will be in the file named 'outputFile'.

By default Mongo prints out first 20 documents IIRC. If you want more you can define new value to batch size in Mongo shell, e.g.

DBQuery.shellBatchSize = 100.

Since you are doing this on a terminal and just want to inspect a record in a sane way, you can use a trick like this:

mongo | tee somefile

Use the session as normal - db.collection.find().pretty() or whatever you need to do, ignore the long output, and exit. A transcript of your session will be in the file tee wrote to.

Be mindful that the output might contain escape sequences and other garbage due to the mongo shell expecting an interactive session. less handles these gracefully.

As answer by Neodan mongoexport is quite useful with -q option for query. It also convert ObjectId to standard format of JSON "$oid". E.g:

mongoexport -d yourdb -c yourcol --jsonArray --pretty -q '{"field": "filter value"}' -o output.json

Using print and JSON.stringify you can simply produce a valid JSON result.
Use --quiet flag to filter shell noise from the output.
Use --norc flag to avoid .mongorc.js evaluation. (I had to do it because of a pretty-formatter that I use, which produces invalid JSON output) Use DBQuery.shellBatchSize = ? replacing ? with the limit of the actual result to avoid paging.

And finally, use tee to pipe the terminal output to a file:

// Shell:
mongo --quiet --norc ./query.js | tee ~/my_output.json

// query.js:
DBQuery.shellBatchSize = 2000;
function toPrint(data) {
  print(JSON.stringify(data, null, 2));
}

toPrint(
  db.getCollection('myCollection').find().toArray()
);

Hope this helps!