mongo提供了help功能，可以帮助我查看一些命令。下面是示例：

> help

db.help() help on db methods

db.mycoll.help() help on collection methods

rs.help() help on replica set methods

help connect connecting to a db help

help admin administrative help

help misc misc things to know

help mr mapreduce help

show dbs show database names

show collections show collections in current database

show users show users in current database

show profile show most recent system.profile entries with time >= 1ms

use <db_name> set current database

db.foo.find() list objects in collection foo

db.foo.find( { a : 1 } ) list objects in foo where a == 1

it result of the last line evaluated; use to further iterate

DBQuery.shellBatchSize = x set default number of items to display on shell

exit quit the mongo shell

> db

admin

> db.help()

DB methods:

db.addUser(username, password[, readOnly=false])

db.auth(username, password)

db.cloneDatabase(fromhost)

db.commandHelp(name) returns the help for the command

db.copyDatabase(fromdb, todb, fromhost)

db.createCollection(name, { size : ..., capped : ..., max : ... } )

db.currentOp() displays the current operation in the db

db.dropDatabase()

db.eval(func, args) run code server-side

db.getCollection(cname) same as db['cname'] or db.cname

db.getCollectionNames()

db.getLastError() - just returns the err msg string

db.getLastErrorObj() - return full status object

db.getMongo() get the server connection object

db.getMongo().setSlaveOk() allow this connection to read from the nonmaster member of a replica pair

db.getName()

db.getPrevError()

db.getProfilingLevel() - deprecated

db.getProfilingStatus() - returns if profiling is on and slow threshold

db.getReplicationInfo()

db.getSiblingDB(name) get the db at the same server as this one

db.isMaster() check replica primary status

db.killOp(opid) kills the current operation in the db

db.listCommands() lists all the db commands

db.printCollectionStats()

db.printReplicationInfo()

db.printSlaveReplicationInfo()

db.printShardingStatus()

db.removeUser(username)

db.repairDatabase()

db.resetError()

db.runCommand(cmdObj) run a database command. if cmdObj is a string, turns it into { cmdObj : 1 }

db.serverStatus()

db.setProfilingLevel(level,<slowms>) 0=off 1=slow 2=all

db.shutdownServer()

db.stats()

db.version() current version of the server

db.getMongo().setSlaveOk() allow queries on a replication slave server

> rs.help()

rs.status() { replSetGetStatus : 1 } checks repl set status

rs.initiate() { replSetInitiate : null } initiates set with default settings

rs.initiate(cfg) { replSetInitiate : cfg } initiates set with configuration cfg

rs.conf() get the current configuration object from local.system.replset

rs.reconfig(cfg) updates the configuration of a running replica set with cfg (disconnects)

rs.add(hostportstr) add a new member to the set with default attributes (disconnects)

rs.add(membercfgobj) add a new member to the set with extra attributes (disconnects)

rs.addArb(hostportstr) add a new member which is arbiterOnly:true (disconnects)

rs.stepDown([secs]) step down as primary (momentarily) (disconnects)

rs.freeze(secs) make a node ineligible to become primary for the time specified

rs.remove(hostportstr) remove a host from the replica set (disconnects)

rs.slaveOk() shorthand for db.getMongo().setSlaveOk()

db.isMaster() check who is primary

reconfiguration helpers disconnect from the database so the shell will display

an error, even if the command succeeds.

see also http://<mongod_host>:28017/_replSet for additional diagnostic info

> db

admin

> show collections

settings

system.indexes

> db.settings.help()

DBCollection help

db.settings.find().help() - show DBCursor help

db.settings.count()

db.settings.dataSize()

db.settings.distinct( key ) - eg. db.settings.distinct( 'x' )

db.settings.drop() drop the collection

db.settings.dropIndex(name)

db.settings.dropIndexes()

db.settings.ensureIndex(keypattern[,options]) - options is an object with these possible fields: name, unique, dropDups

db.settings.reIndex()

db.settings.find([query],[fields]) - query is an optional query filter. fields is optional set of fields to return.

e.g. db.settings.find( {x:77} , {name:1, x:1} )

db.settings.find(...).count()

db.settings.find(...).limit(n)

db.settings.find(...).skip(n)

db.settings.find(...).sort(...)

db.settings.findOne([query])

db.settings.findAndModify( { update : ... , remove : bool [, query: {}, sort: {}, 'new': false] } )

db.settings.getDB() get DB object associated with collection

db.settings.getIndexes()

db.settings.group( { key : ..., initial: ..., reduce : ...[, cond: ...] } )

db.settings.mapReduce( mapFunction , reduceFunction , <optional params> )

db.settings.remove(query)

db.settings.renameCollection( newName , <dropTarget> ) renames the collection.

db.settings.runCommand( name , <options> ) runs a db command with the given name where the first param is the collection name

db.settings.save(obj)

db.settings.stats()

db.settings.storageSize() - includes free space allocated to this collection

db.settings.totalIndexSize() - size in bytes of all the indexes

db.settings.totalSize() - storage allocated for all data and indexes

db.settings.update(query, object[, upsert_bool, multi_bool])

db.settings.validate() - SLOW

db.settings.getShardVersion() - only for use with sharding

>

 

如果在输入函数的时候，不加上左右括号会怎么样呢？注意看mongo提示出来的是这个函数的JS源码。通过这个小技巧，你可以了解这个函数的实现方法，以及它的参数及顺序：

> db.settings.insert

function (obj, _allow_dot) {

if (!obj) {

throw "no object passed to insert!";

}

if (!_allow_dot) {

this._validateForStorage(obj);

}

if (typeof obj._id == "undefined") {

var tmp = obj;

obj = {_id:new ObjectId};

for (var key in tmp) {

obj[key] = tmp[key];

}

}

this._mongo.insert(this._fullName, obj);

this._lastID = obj._id;

}