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PSUBSCRIBE

Subscribes the client to channels matching the specified patterns.

Syntax​

PSUBSCRIBE pattern [pattern ...]

Parameters​

  • pattern: One or more patterns to subscribe to. Patterns can include the wildcard character * to match multiple channels.

Details​

  • Available since: 1.0.0
  • Time complexity: O(1) for each subscription. The time complexity depends on the number of channels matched by the patterns.
  • ACL categories: @pubsub, @read

The PSUBSCRIBE command allows a client to subscribe to multiple channels simultaneously using patterns. The client will receive messages published to channels that match the specified patterns. The command uses pattern matching, where * can be used to match any number of characters.

When a message is published to a channel matching one of the patterns, the client receives the message along with the name of the channel.

Examples​

Basic Usage​

To subscribe to all channels that start with "news":

PSUBSCRIBE news*

With this subscription, the client will receive messages published to channels like news.sports, news.weather, etc.

Multiple Patterns​

To subscribe to channels matching multiple patterns:

PSUBSCRIBE news* sport* tech*

The client will receive messages published to channels like news.sports, sport.football, tech.gadgets, etc.

Using Wildcards​

To subscribe to all channels:

PSUBSCRIBE *

This subscription will capture messages from all channels.

Edge Cases​

  • If the pattern includes spaces or special characters, ensure proper escaping or quoting in the command.
  • Subscriptions to invalid patterns or empty patterns are handled as normal subscriptions and will not return errors.

RESP2/RESP3 Reply​

  • Array reply: The command returns an array containing the following elements:
    1. The message type subscribe.
    2. The pattern that was subscribed to.
    3. The number of patterns to which the client is currently subscribed.

Example reply for PSUBSCRIBE news*:

1) "psubscribe"
2) "news*"
3) (integer) 1
  • If the command is sent after a SUBSCRIBE command, the client will receive additional replies indicating both pattern-based and direct subscriptions.

Notes​

  • The PSUBSCRIBE command is used in conjunction with the PUBLISH command for pattern-based messaging in Redis.
  • To unsubscribe from patterns, use the PUNSUBSCRIBE command.