MongoDB - The mongo Shell, Write Scripts for the mongo Shell

内容导读

互联网集市收集整理的这篇技术教程文章主要介绍了MongoDB - The mongo Shell, Write Scripts for the mongo Shell，小编现在分享给大家，供广大互联网技能从业者学习和参考。文章包含4997字，纯文字阅读大概需要8分钟。

内容图文

This tutorial provides an introduction to writing JavaScript that uses the mongo shell to access MongoDB.

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();
2016-12-01T00:09:03.664+0800 I NETWORK  [initandlisten] connection accepted from 127.0.0.1:29118 #8 (8 connections now open)
connection to 127.0.0.1
> db = conn.getDB("myDatabase");
myDatabase

If connecting to a MongoDB instance that enforces access control, you can use the db.auth() method to authenticate.

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 27020and set the global db variable:

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

SEE ALSO: mongo Shell Methods

Differences Between Interactive and Scripted mongo

When writing scripts for the mongo shell, consider the following:

• 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.

• Write operations in the mongo shell use a write concern of { w: 1 } by default. If performing bulk operations, use the Bulk() methods. See Write Method Acknowledgements for more information.

  Changed in version 2.6: Before MongoDB 2.6, call db.getLastError() explicitly to wait for the result of write operations.

• You cannot use any shell helper (e.g. use <dbname>, show dbs, etc.) inside the JavaScript file because they are not valid JavaScript.

  The following table maps the most common mongo shell helpers to their JavaScript equivalents.

  Shell Helpers	JavaScript Equivalents
  show dbs, show databases	db.adminCommand(‘listDatabases‘)
  use <db>	db = db.getSiblingDB(‘<db>‘)
  show collections	db.getCollectionNames()
  show users	db.getUsers()
  show roles	db.getRoles({showBuiltinRoles: true})
  show log <logname>	db.adminCommand({ ‘getLog‘ : ‘<logname>‘ })
  show logs	db.adminCommand({ ‘getLog‘ : ‘*‘ })
  it	cursor = db.collection.find()  if ( cursor.hasNext() ){      cursor.next();  }

• In interactive mode, mongo prints the results of operations including the content of all cursors. In scripts, either use the JavaScript print() function or the mongo specific printjson() function which returns formatted JSON.

  To print all items in a result cursor in mongo shell scripts, use the following idiom:

  cursor = db.collection.find();
  while ( cursor.hasNext() ) {
      printjson( cursor.next() );
  }

Scripting

From the system prompt, use mongo to evaluate JavaScript.

--eval option

Use the --eval option to mongo to pass the shell a JavaScript fragment, as in the following:

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

This returns the output of db.getCollectionNames() using the mongo shell connected to the mongod or mongos instance running on port 27017 on the localhost interface.

Execute a JavaScript file

You can specify a .js file to the mongo shell, and mongo will execute the JavaScript directly. Consider the following example:

mongo localhost:27017/test myjsfile.js

This operation executes the myjsfile.js script in a mongo shell that connects to the test database on the mongod instance accessible via the localhost interface on port 27017.

Alternately, you can specify the mongodb connection parameters inside of the javascript file using the Mongo() constructor. See Opening New Connections for more information.

You can execute a .js file from within the mongo shell, using the load() function, as in the following:

load("myjstest.js")

This function loads and executes the myjstest.js file.

The load() method accepts relative and absolute paths. If the current working directory of the mongo shell is /data/db, and the myjstest.js resides in the /data/db/scripts directory, then the following calls within the mongo shell would be equivalent:

load("scripts/myjstest.js")
load("/data/db/scripts/myjstest.js")

NOTE: There is no search path for the load() function. If the desired script is not in the current working directory or the full specified path, mongo will not be able to access the file.

MongoDB - The mongo Shell, Write Scripts for the mongo Shell

标签：man   ssi   onchange   returns   control   following   ror   scripts   lua   

本文系统来源：http://www.cnblogs.com/huey/p/6120368.html

内容总结

以上是互联网集市为您收集整理的MongoDB - The mongo Shell, Write Scripts for the mongo Shell全部内容，希望文章能够帮你解决MongoDB - The mongo Shell, Write Scripts for the mongo Shell所遇到的程序开发问题。 如果觉得互联网集市技术教程内容还不错，欢迎将互联网集市网站推荐给程序员好友。

内容备注

版权声明：本文内容由互联网用户自发贡献，该文观点与技术仅代表作者本人。本站仅提供信息存储空间服务，不拥有所有权，不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容， 请发送邮件至 gblab@vip.qq.com 举报，一经查实，本站将立刻删除。

内容手机端