$rtrim (aggregation)

Definition

$rtrim

Removes whitespace characters, including null, or the specified characters from the end of a string.

$rtrim has the following syntax:

{ $rtrim: { input: <string>,  chars: <string> } }

The $rtrim takes a document with the following fields:

Field	Description
input	The string to trim. The argument can be any valid expression that resolves to a string. For more information on expressions, see Expressions.
chars	Optional. The character(s) to trim from the end of the input. The argument can be any valid expression that resolves to a string. The $rtrim operator breaks down the string into individual UTF code point to trim from input. If unspecified, $rtrim removes whitespace characters, including the null character. For the list of whitespace characters, see Whitespace Characters.

Tip

See also:

• $ltrim

• $trim

Behavior

• By default, $rtrim removes whitespace, including the null character, from the end of the input string:

  Example	Results
  { $rtrim: { input: " \n good bye \t " } }	" \n good bye"

• You can override the default characters to trim using the chars field.

  For example, the following trims any g and e from the end of the input string. Since the input ends with a whitespace, neither character can be trimmed from the end of the string.

  Example	Results
  { $rtrim: { input: "ggggoodbyeeeee ", chars: "ge" } }	"ggggoodbyeeeee "

• If overriding the default characters to trim, you can explicitly include the whitespace character(s) to trim in the chars field.

  For example, the following trims any space or e from the end of the input string.

  Example	Results
  { $rtrim: { input: " ggggoodbyeeeee ", chars: "e " } }	" ggggoodby"

Example

Consider an inventory collection with the following documents:

{ "_id" : 1, "item" : "ABC1", quarter: "13Q1", "description" : " product 1" }
{ "_id" : 2, "item" : "ABC2", quarter: "13Q4", "description" : "product 2 \n The product is in stock.  \n\n  " }
{ "_id" : 3, "item" : "XYZ1", quarter: "14Q2", "description" : null }

The following operation uses the $rtrim operator to remove trailing whitespace from the description field:

db.inventory.aggregate([
   { $project: { item: 1, description: { $rtrim: { input: "$description" } } } }
])

The operation returns the following results:

{ "_id" : 1, "item" : "ABC1", "description" : " product 1" }
{ "_id" : 2, "item" : "ABC2", "description" : "product 2 \n The product is in stock." }
{ "_id" : 3, "item" : "XYZ1", "description" : null }