问题

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

回答1:

AFAIK, there is no a interactive option for output to file, there is a previous SO question related with this: Printing mongodb shell output to File

However, you can log all the shell session if you invoked the shell with tee command:

$ mongo | tee file.txt
MongoDB shell version: 2.4.2
connecting to: test
> printjson({this: 'is a test'})
{ "this" : "is a test" }
> printjson({this: 'is another test'})
{ "this" : "is another test" }
> exit
bye

Then you'll get a file with this content:

MongoDB shell version: 2.4.2
connecting to: test
> printjson({this: 'is a test'})
{ "this" : "is a test" }
> printjson({this: 'is another test'})
{ "this" : "is another test" }
> exit
bye

To remove all the commands and keep only the json output, you can use a command similar to:

tail -n +3 file.txt | egrep -v "^>|^bye" > output.json

Then you'll get:

{ "this" : "is a test" }
{ "this" : "is another test" }

回答2:

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

回答3:

We can do it this way -

mongo db_name --quiet --eval 'DBQuery.shellBatchSize = 2000; db.users.find({}).limit(2000)' > users.json

The shellBatchSize argument is used to determine how many rows is the mongo client allowed to print. Its default value is 20.

回答4:

Combining several conditions:

write mongo query in JS file and send it from terminal
switch/define a database programmatically
output all found records
cut initial output lines
save the output into JSON file

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

回答5:

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 :)

(from : https://stackoverflow.com/a/3705615/1290746)

来源：https://stackoverflow.com/questions/22565231/printing-mongo-query-output-to-a-file-while-in-the-mongo-shell

标签

mongodb

mongodb-query

mongo-shell

Printing Mongo query output to a file while in the mongo shell