[Mr. Zhao Qiang] use mongodb’s command line tool: mongoshell

Time:2021-10-18

1、 Start Mongo shell

After mongodb is installed, execute the following commands directly on the command line terminal:

mongo

As shown in the figure below:

The optional parameters are as follows:

It can also be abbreviated as:

To use an external editor in Mongo shell, such as: VI, you only need to set the environment variable:

export EDITOR=vi

Start Mongo shell. Let’s edit a function in Mongo shell:

Define function:

function myFunction () { }

Edit function:

edit myFunction
function myFunction() {print("Hello World") }

2、 Startup configuration file for Mongo shell. Mongorc.js

When started, Mongo checks a JavaScript file. Mongorc. JS in the user’s home directory. If found, Mongo parses the contents of. Mongorc.js before displaying the prompt for the first time. If you use the shell to execute a JavaScript file or calculation expression, either use the — Eval option on the command line or specify a. JS file to Mongo. Mongo will read the. Mongorc.js file after JavaScript processing. You can use the — NORC option to prevent loading. Mongorc. JS.

  • Create a prompt for the number of operations issued with the current session, and define the following variables:
cmdCount = 1;
prompt = function() {
    return "mongo " + (cmdCount++) + "> ";
}

The effects are as follows:

  • Display the database name and host name in the Mongo shell:
host = db.serverStatus().host;
cmdCount = 1;
prompt = function() {
    return db+"@"+host+" " + (cmdCount++) + "> ";
}

The effects are as follows:

3、 Basic operation of Mongo shell

  • To display the current database name, enter the following command. The test database is returned, which is the default database:
db
  • Switch database:
use 
  • View all available databases:
Show DBS or show databases
  • We can switch to a nonexistent database. When we store data for the first time, mongodb will automatically create the database. For example, the following example inserts a piece of data, which will create both database (mynewdatabase) and collection (mycollection)

 

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