Redis CLI (redis-cli) basics

Introduction

Redis CLI lets you talk directly to Redis to store, get, and manage data quickly and simply.

You want to quickly check or change data in Redis without writing a program.

You need to test Redis commands to learn how they work.

You want to debug or monitor Redis data during development.

You want to run simple Redis commands from your computer terminal.

You want to explore Redis features interactively.

Syntax

Redis

redis-cli [options] [command] [arguments]

You type commands after redis-cli prompt to interact with Redis.

Commands are simple words like SET, GET, DEL followed by keys or values.

Examples

Connect to Redis, store the word Hello under mykey, then get it back.

Redis

redis-cli
SET mykey "Hello"
GET mykey

Delete the key named mykey from Redis.

Redis

redis-cli DEL mykey

Increase the number stored in counter by 1.

Redis

redis-cli INCR counter

Sample Program

This stores a greeting message and then retrieves it.

Redis

redis-cli
SET greeting "Hi there!"
GET greeting

Important Notes

Commands are case-insensitive but usually written in uppercase for clarity.

If Redis is on another computer or port, use -h and -p options to connect.

Use CTRL+C to exit redis-cli interactive mode.

Summary

redis-cli is a simple tool to send commands to Redis.

You can set, get, delete, and modify data easily.

It helps you learn and test Redis commands quickly.

Practice

1. What does the Redis CLI command SET key value do?

easy

A. Retrieves the value of the key

B. Deletes the key from Redis

C. Stores the value under the given key in Redis

D. Lists all keys in Redis

Solution

1. Step 1: Understand the SET command

   The SET command in Redis stores a value under a specified key.

2. Step 2: Match command to action

   Since SET assigns a value to a key, it stores data rather than deleting or retrieving it.

3. Final Answer:

   Stores the value under the given key in Redis -> Option C

4. Quick Check:

   SET command = store value [OK]

Hint: SET means store a value for a key [OK]

Common Mistakes:

• Confusing SET with GET
• Thinking SET deletes keys
• Assuming SET lists keys

2. Which of the following is the correct syntax to get the value of a key named user1 in Redis CLI?

easy

A. KEYS user1

B. GET user1

C. DEL user1

D. SET user1

Solution

1. Step 1: Identify the command to retrieve a value

   The GET command is used to fetch the value stored at a key in Redis.

2. Step 2: Check syntax correctness

   GET followed by the key name is the correct syntax to get the value of 'user1'.

3. Final Answer:

   GET user1 -> Option B

4. Quick Check:

   GET command syntax = GET key [OK]

Hint: GET retrieves value, SET stores, DEL deletes [OK]

Common Mistakes:

• Using SET instead of GET
• Using DEL to get value
• Using KEYS to get value

3. What will be the output of the following Redis CLI commands?

SET count 10
INCR count
GET count

medium

A. "11"

B. "10"

C. Error: wrong type operation

D. nil

Solution

1. Step 1: Analyze the commands step-by-step

   SET count 10 stores the string "10" under key 'count'. INCR count increments the integer value by 1.

2. Step 2: Understand INCR effect and GET result

   INCR converts the string "10" to integer 10, adds 1 to make 11. GET count returns "11" as a string.

3. Final Answer:

   "11" -> Option A

4. Quick Check:

   INCR on "10" = "11" [OK]

Hint: INCR adds 1 to numeric string values [OK]

Common Mistakes:

• Expecting original value "10"
• Thinking INCR causes error
• Expecting nil for existing key

4. You run the command GET mykey but get an error: WRONGTYPE Operation against a key holding the wrong kind of value. What is the likely cause?

medium

A. The key holds a non-string value like a list or set

B. The key does not exist

C. The Redis server is down

D. The GET command is misspelled

Solution

1. Step 1: Understand the error message

   The error means GET was used on a key that stores a data type other than string, like a list or set.

2. Step 2: Identify the cause from options

   Since the key exists but is not a string, GET cannot retrieve it, causing the error.

3. Final Answer:

   The key holds a non-string value like a list or set -> Option A

4. Quick Check:

   WRONGTYPE error = wrong data type for GET [OK]

Hint: GET works only on string keys, not lists or sets [OK]

Common Mistakes:

• Thinking key does not exist
• Assuming server is down
• Misspelling GET causes this error

5. You want to store a user's name and age in Redis using redis-cli. Which sequence of commands correctly stores the name "Alice" and age 30, then retrieves both values?

hard

A. SET user:name Alice
SET user:age 30
HGET user:name
HGET user:age

B. LPUSH user Alice 30
LRANGE user 1 1

C. SET user Alice 30
GET user

D. HSET user name Alice age 30
HGET user name
HGET user age

Solution

1. Step 1: Identify the best data structure for multiple fields

   Using a hash (HSET) allows storing multiple fields like name and age under one key.

2. Step 2: Check commands for storing and retrieving fields

   HSET user name Alice age 30 stores both fields. HGET user name and HGET user age retrieve them separately.

3. Final Answer:

   HSET user name Alice age 30 HGET user name HGET user age -> Option D

4. Quick Check:

   Use hashes for multiple related fields [OK]

Hint: Use HSET/HGET for multiple fields in one key [OK]

Common Mistakes:

• Using SET with multiple values
• Using list commands for key-value pairs
• Trying to GET multiple values at once