Redis Basic Commands and Key Operations Tutorial

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1. Basic Redis Commands 127.0.0.1:6379> ping PONG 127.0.0.1:6379> DBSIZE (integer) 0 127.0.0.1:6379> SELECT 5 # Switch to database 5 (databases are indexed from 0 to 15)

OK 127.0.0.1:6379[5]> DBSIZE (integer) 0 127.0.0.1:6379[5]> set k1 v2 OK 127.0.0.1:6379[5]> set k2 v1 OK 127.0.0.1:6379[5]> DBSIZE (integer) 2

Delete all data in the current database: FLUSHDB 127.0.0.1:6379[5]> FLUSHDB OK 127.0.0.1:6379[5]> DBSIZE (integer) 0

2. Redis Key Operations

A. Syntax: keys pattern

Purpose: Find all keys matching the given pattern; the pattern can use wildcards.

* matches zero or more characters (e.g., keys * lists all keys – not recommended in production).

? matches a single character (e.g., keys he?lo matches hello and heolo). 127.0.0.1:6379> set k1 v1 OK 127.0.0.1:6379> set k2 v3 OK 127.0.0.1:6379> keys * 1) "k2"

2) "k1" 127.0.0.1:6379> set hello hello OK 127.0.0.1:6379> set heolo heolo OK 127.0.0.1:6379> keys he?lo 1) "heolo"

2) "hello"

B. exists

Check whether a key exists. 127.0.0.1:6379> EXISTS hello (integer) 1 127.0.0.1:6379> EXISTS helol (integer) 0 127.0.0.1:6379> EXISTS heolo (integer) 1

C. expire

Set a key’s time‑to‑live (TTL) in seconds; returns 1 if the timeout was set, 0 otherwise.

D. ttl

Returns the remaining TTL of a key in seconds.

-1: key has no expiration (never expires).

-2: key does not exist. 127.0.0.1:6379> ttl k1 # The key currently has no expiration

(integer) -1 127.0.0.1:6379> EXPIRE k1 20 # Set k1 to expire after 20 seconds

(integer) 1 127.0.0.1:6379> ttl k1 # 15 seconds remaining

(integer) 15 127.0.0.1:6379> ttl k1 # 11 seconds remaining

(integer) 11 127.0.0.1:6379> ttl k1 # 2 seconds remaining

(integer) 2 127.0.0.1:6379> ttl k1 # After expiration, the key is removed

(integer) -2 127.0.0.1:6379> keys * # Verify remaining keys

1) "heolo"

2) "k2"

3) "hello"

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Recommended Reading:

Redis Advantages and Remote Client Connections

Redis Data Backup and Restoration

Setting Up Redis Sentinel

Redis Sentinel and Master‑Slave Replication

Detailed Summary of Redis Configuration Files