2 days old with Mongo and I have a SQL background so bear with me. As with mysql, it is very convenient to be in the MySQL command line and output the results of a query to a file on the machine. I am trying to understand how I can do the same with Mongo, while being in the shell
I can easily get the output of a query I want by being outside of the shell and executing the following command:
mongo localhost:27017/dbname --eval "printjson(db.collectionName.findOne())" > sample.json
The above way is fine, but it requires me to exit the mongo shell or open a new terminal tab to execute this command. It would be very convenient if I could simply do this while still being inside the shell.
P.S: the Question is an offshoot of a question I posted on SO
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If you invoke the shell with script-file, db address, and --quiet arguments, you can redirect the output (made with print() for example) to a file:
mongo localhost/mydatabase --quiet myScriptFile.js > output
It may be useful to you to simply increase the number of results that get displayed
In the mongo shell >
DBQuery.shellBatchSize = 3000
and then you can select all the results out of the terminal in one go and paste into a text file.
It is what I am going to do :)
There are ways to do this without having to quit the CLI and pipe mongo
output to a non-tty.
To save the output from a query with result x
we can do the following to directly store the json output to /tmp/x.json
:
> EDITOR="cat > /tmp/x.json"
> x = db.MyCollection.find(...).toArray()
> edit x
>
Note that the output isn't strictly Json but rather the dialect that Mongo uses.
We can do it this way -
mongo db_name --quiet --eval 'DBQuery.shellBatchSize = 2000; db.users.find({}).limit(2000).toArray()' > users.json
The shellBatchSize
argument is used to determine how many rows is the mongo client allowed to print. Its default value is 20.
myScriptFile.js
// Switch current database to "mydatabase"
db = db.getSiblingDB('mydatabase');
// The mark for cutting initial output off
print("CUT_TO_HERE");
// Main output
// "toArray()" method allows to get all records
printjson( db.getCollection('jobs').find().toArray() );
Sending the query from terminal
-z
key of sed
allows treat output as a single multi-line string
$> mongo localhost --quiet myScriptFile.js | sed -z 's/^.*CUT_TO_HERE\n//' > output.json
Source: Stackoverflow.com