Command: STR.APPEND

Overview

The STR.APPEND command is used to append one or more string values to an existing string stored at a given key. If the key does not exist, it creates a new entry with the concatenated value.

Command Name

STR.APPEND

Description

Appends the provided string values to the end of the string currently stored at the specified key. If the key does not exist, a new string is created. If the existing value is not a string, an error is returned.

Use Cases

Append Logging Entries

You can use STR.APPEND to build log-like string values that grow with each log message:

  STR.APPEND log:serviceA "[INFO] Started"
STR.APPEND log:serviceA " [DEBUG] Listening on port 8080"
Construct Responses

Build dynamic string responses over time based on state or input:

  STR.APPEND response:user42 "Hello "

STR.APPEND response:user42 "World"
Progressive Key Initialization

Initialize a new key and keep updating it in different steps:

  STR.APPEND init:flow "Step1"

STR.APPEND init:flow " -> Step2"

Syntax 

  STR.APPEND <key> <value> [<value> ...]

  • <key> : Required. The key of the existing or new string.

  • <value> : One or more strings to append.

Permissions

  • Read & Write access on the specified key.

  • Internal shard lookup is based on the key for distributed storage compatibility.

Input Examples

Append to a non-existent key 
  localhost:9219> STR.APPEND key1 "Hello"

Ok
Append to an existing key 
  localhost:9219> STR.APPEND key1 " World"

Ok
Append multiple values 
  localhost:9219> STR.APPEND key1 " and" " John"

Ok

Output Examples

After appending: 
  localhost:9219> GET key1

Ok "Hello World and John"

Behavior on Error

Error Condition Message
No key provided InvalidKeyError: Key must be provided
Key name fails validation InvalidKeyError: <validation reason>
Value at key is not of type string InvalidValueError: the existing value for the provided key must be a string
Storage backend error while setting the value <error from store.M.Set>