写脚本

Opening New Connections¶

From the mongo shell or from a JavaScript file, you can instantiate database connections using the Mongo() constructor:

new Mongo()
new Mongo(<host>)
new Mongo(<host:port>)

Consider the following example that instantiates a new connection to the MongoDB instance running on localhost on the default port and sets the global db variable to myDatabase using the getDB() method:

conn = new Mongo();
db = conn.getDB("myDatabase");

Additionally, you can use the connect() method to connect to the MongoDB instance. The following example connects to the MongoDB instance that is running on localhost with the non-default port 27020 and set the global db variable:

db = connect("localhost:27020/myDatabase");

If you create new connections inside a JavaScript file:

• You cannot use use <dbname> inside the file to set the db global variable.
• To set the db global variable, use the getDB() method or the connect() method. You can assign the database reference to a variable other than db.
• Additionally, inside the script, you would need to call db.getLastErrorObj() or db.getLastError() explicitly to wait for the result of write operations.

Scripting¶

From the command line, use mongo to evaluate JavaScript.

mongo test --eval "printjson(db.getCollectionNames())"

mongo localhost:27017/test myjsfile.js