Redis Command: LTRIM

by

Summary

Command NameLTRIM
UsageTrim list to start and stop indexes
Group list
ACL Category@write
@list
@slow
Time ComplexityO(N)
FlagWRITE
Arity4

Notes

  • In the time complexity, N is the number of removed items.

Signature

LTRIM <key> <start> <stop>

Usage

Trim a Redis list, and remove items from the list from one or both end(s). We provide a starting and ending index for the trim and the items outside that window are removed.

Redis LTRIM command example
Redis LTRIM command example

Notes

  • If all items are removed while trimming, then the list is deleted.
  • Indexes are Zero(0) based.
  • Both positive and negative indexing works for this command.

Arguments

ParameterDescriptionNameType
<key>Key name of the listkeykey
<start>Index to start trimmingstartinteger
<stop>Index to stop trimmingstopinteger

Return Value

Return valueCase for the return valueType
OKIf the operation was successful, and the list existsconst
errorIf the command applied on data other than a listerror

Notes

  • If key is not of type list, the following error message is returned-
    (error) WRONGTYPE Operation against a key holding the wrong kind of value

Examples

Here are a few examples of the LTRIM command usage-

# Redis LTRIM command examples

# Push items and create list
127.0.0.1:6379> rpush bigboxlist B I G B O X C O D E B I O
(integer) 13

# Check list
127.0.0.1:6379> lrange bigboxlist 0 -1
 1) "B"
 2) "I"
 3) "G"
 4) "B"
 5) "O"
 6) "X"
 7) "C"
 8) "O"
 9) "D"
10) "E"
11) "B"
12) "I"
13) "O"

# Trim items outside of index 3 to the end
127.0.0.1:6379> ltrim bigboxlist 3 -1
OK

# Check list. Initial 3 items are deleted
127.0.0.1:6379> lrange bigboxlist 0 -1
 1) "B"
 2) "O"
 3) "X"
 4) "C"
 5) "O"
 6) "D"
 7) "E"
 8) "B"
 9) "I"
10) "O"

# Keep items from index 0 to 6 and delete others
127.0.0.1:6379> ltrim bigboxlist 0 6
OK

# Check list
127.0.0.1:6379> lrange bigboxlist 0 -1
1) "B"
2) "O"
3) "X"
4) "C"
5) "O"
6) "D"
7) "E"

# Try to trim by keeping items from index 3 to 100
# Max index in existing list is 6. So it will use 6 instead of 100
127.0.0.1:6379> ltrim bigboxlist 3 100
OK

# Check list
127.0.0.1:6379> lrange bigboxlist 0 -1
1) "C"
2) "O"
3) "D"
4) "E"

# Provide ltrim indexes where start index is larger
# This will empty the list
127.0.0.1:6379> ltrim bigboxlist 2 1
OK

# Check list, the list is empty now
127.0.0.1:6379> lrange bigboxlist 0 -1
(empty array)

# Try to trim a list that does not exist
# It will return OK
127.0.0.1:6379> ltrim nonexistinglist 0 1
OK

# Set a string
127.0.0.1:6379> set bigboxstr "Some string for test"
OK

# Try to use LTRIM on a string
# we get an error
127.0.0.1:6379> ltrim bigboxstr 0 1
(error) WRONGTYPE Operation against a key holding the wrong kind of value

Notes

  • If the <start> or <stop> index is out of range then, the command will adjust to the max/min possible index.
  • If <start> is larger than <stop> then the LTRIM command will return an empty list.
  • If we try to use LTRIM on a list that does not exist, then it will return “OK”. Nothing else will happen.

Code Implementations

Here are the usage examples of the Redis LTRIM command in different programming languages.

// Redis LTRIM command example in Golang

package main

import (
	"context"
	"fmt"

	"github.com/redis/go-redis/v9"
)

var rdb *redis.Client
var ctx context.Context

func init() {
	rdb = redis.NewClient(&redis.Options{
		Addr:     "localhost:6379",
		Username: "default",
		Password: "",
		DB:       0,
	})

	ctx = context.Background()
}

func main() {

	// Push items and create list
	// Command: rpush bigboxlist B I G B O X C O D E B I O
	// Result: (integer) 13
	rpushResult, err := rdb.RPush(ctx, "bigboxlist", "B", "I", "G", "B", "O", "X", "C", "O", "D", "E", "B", "I", "O").Result()

	if err != nil {
		fmt.Println("Command: rpush bigboxlist B I G B O X C O D E B I O | Error: " + err.Error())
	}

	fmt.Println("Command: rpush bigboxlist B I G B O X C O D E B I O | Result: ", rpushResult)

	// Check list
	// Command: lrange bigboxlist 0 -1
	// Result:
	//         1) "B"  2) "I"  3) "G"  4) "B"  5) "O"  6) "X"  7) "C"  8) "O"  9) "D"  10) "E"  11) "B"  12) "I"  13) "O"
	lrangeResult, err := rdb.LRange(ctx, "bigboxlist", 0, -1).Result()

	if err != nil {
		fmt.Println("Command: lrange bigboxlist 0 -1 | Error: " + err.Error())
	}

	fmt.Println("Command: lrange bigboxlist 0 -1 | Result: ", lrangeResult)

	// Trim items outside of index 3 to the end
	// Command: ltrim bigboxlist 3 -1
	// Result: OK
	ltrimResult, err := rdb.LTrim(ctx, "bigboxlist", 3, -1).Result()

	if err != nil {
		fmt.Println("Command: ltrim bigboxlist 3 -1 | Error: " + err.Error())
	}

	fmt.Println("Command: ltrim bigboxlist 3 -1 | Result: " + ltrimResult)

	// Check list. Initial 3 items are deleted
	// Command: lrange bigboxlist 0 -1
	// Result:
	//         1) "B"  2) "O"  3) "X"  4) "C"  5) "O"  6) "D"  7) "E"  8) "B"  9) "I"  10) "O"
	lrangeResult, err = rdb.LRange(ctx, "bigboxlist", 0, -1).Result()

	if err != nil {
		fmt.Println("Command: lrange bigboxlist 0 -1 | Error: " + err.Error())
	}

	fmt.Println("Command: lrange bigboxlist 0 -1 | Result: ", lrangeResult)

	// Keep items from index 0 to 6 and delete others
	// Command: ltrim bigboxlist 0 6
	// Result: OK
	ltrimResult, err = rdb.LTrim(ctx, "bigboxlist", 0, 6).Result()

	if err != nil {
		fmt.Println("Command: ltrim bigboxlist 0 6 | Error: " + err.Error())
	}

	fmt.Println("Command: ltrim bigboxlist 0 6 | Result: " + ltrimResult)

	// Check list
	// Command: lrange bigboxlist 0 -1
	// Result:
	//         1) "B"  2) "O"  3) "X"  4) "C"  5) "O"  6) "D"  7) "E"
	lrangeResult, err = rdb.LRange(ctx, "bigboxlist", 0, -1).Result()

	if err != nil {
		fmt.Println("Command: lrange bigboxlist 0 -1 | Error: " + err.Error())
	}

	fmt.Println("Command: lrange bigboxlist 0 -1 | Result: ", lrangeResult)

	// Try to trim by keeping items from index 3 to 100
	// Max index in existing list is 6. So it will use 6 instead of 100
	// Command: ltrim bigboxlist 3 100
	// Result: OK
	ltrimResult, err = rdb.LTrim(ctx, "bigboxlist", 3, 100).Result()

	if err != nil {
		fmt.Println("Command: ltrim bigboxlist 3 100 | Error: " + err.Error())
	}

	fmt.Println("Command: ltrim bigboxlist 3 100 | Result: " + ltrimResult)

	// Check list
	// Command: lrange bigboxlist 0 -1
	// Result:
	//         1) "C"  2) "O"  3) "D"  4) "E"
	lrangeResult, err = rdb.LRange(ctx, "bigboxlist", 0, -1).Result()

	if err != nil {
		fmt.Println("Command: lrange bigboxlist 0 -1 | Error: " + err.Error())
	}

	fmt.Println("Command: lrange bigboxlist 0 -1 | Result: ", lrangeResult)

	// Provide ltrim indexes where start index is larger
	// This will empty the list
	// Command: ltrim bigboxlist 2 1
	// Result: OK
	ltrimResult, err = rdb.LTrim(ctx, "bigboxlist", 2, 1).Result()

	if err != nil {
		fmt.Println("Command: ltrim bigboxlist 2 1 | Error: " + err.Error())
	}

	fmt.Println("Command: ltrim bigboxlist 2 1 | Result: " + ltrimResult)

	// Check list, the list is empty now
	// Command: lrange bigboxlist 0 -1
	// Result: (empty array)
	lrangeResult, err = rdb.LRange(ctx, "bigboxlist", 0, -1).Result()

	if err != nil {
		fmt.Println("Command: lrange bigboxlist 0 -1 | Error: " + err.Error())
	}

	fmt.Println("Command: lrange bigboxlist 0 -1 | Result: ", lrangeResult)

	// Try to trim a list that does not exist
	// It will return OK
	// Command: ltrim nonexistinglist 0 1
	// Result: OK
	ltrimResult, err = rdb.LTrim(ctx, "bigboxlist", 0, 1).Result()

	if err != nil {
		fmt.Println("Command: ltrim nonexistinglist 0 1 | Error: " + err.Error())
	}

	fmt.Println("Command: ltrim nonexistinglist 0 1 | Result: " + ltrimResult)

	// Set a string
	// Command: set bigboxstr "Some string for test"
	// Result: OK
	setResult, err := rdb.Set(ctx, "bigboxstr", "Some string for test", 0).Result()

	if err != nil {
		fmt.Println("Command: set bigboxstr "Some string for test" | Error: " + err.Error())
	}

	fmt.Println("Command: set bigboxstr "Some string for test" | Result: " + setResult)

	// Try to use LTRIM on a string
	// we get an error
	// Command: ltrim bigboxstr 0 1
	// Result: (error) WRONGTYPE Operation against a key holding the wrong kind of value
	ltrimResult, err = rdb.LTrim(ctx, "bigboxstr", 0, 1).Result()

	if err != nil {
		fmt.Println("Command: ltrim bigboxstr 0 1 | Error: " + err.Error())
	}

	fmt.Println("Command: ltrim bigboxstr 0 1 | Result: " + ltrimResult)

}

Output:

Command: rpush bigboxlist B I G B O X C O D E B I O | Result:  13
Command: lrange bigboxlist 0 -1 | Result:  [B I G B O X C O D E B I O]

Command: ltrim bigboxlist 3 -1 | Result: OK
Command: lrange bigboxlist 0 -1 | Result:  [B O X C O D E B I O]

Command: ltrim bigboxlist 0 6 | Result: OK
Command: lrange bigboxlist 0 -1 | Result:  [B O X C O D E]

Command: ltrim bigboxlist 3 100 | Result: OK
Command: lrange bigboxlist 0 -1 | Result:  [C O D E]

Command: ltrim bigboxlist 2 1 | Result: OK
Command: lrange bigboxlist 0 -1 | Result:  []

Command: ltrim nonexistinglist 0 1 | Result: OK

Command: set bigboxstr "Some string for test" | Result: OK
Command: ltrim bigboxstr 0 1 | Error: WRONGTYPE Operation against a key holding the wrong kind of value
Command: ltrim bigboxstr 0 1 | Result:

Notes

  • Use “LTrim” method from redis-go module.
  • Signature of the method is-
    func (c cmdable) LTrim(ctx context.Context, key string, start, stop int64) *StatusCmd
// Redis LTRIM command example in JavaScript(NodeJS)

import { createClient } from "redis";

// Create redis client
const redisClient = createClient({
  url: "redis://default:@localhost:6379",
});

await redisClient.on("error", (err) =>
  console.log("Error while connecting to Redis", err)
);

// Connect Redis client
await redisClient.connect();

/**
 * Push items and create list
 * Command: rpush bigboxlist B I G B O X C O D E B I O
 * Result: (integer) 13
 */
let commandResult = await redisClient.rPush("bigboxlist", [
  "B",
  "I",
  "G",
  "B",
  "O",
  "X",
  "C",
  "O",
  "D",
  "E",
  "B",
  "I",
  "O",
]);

console.log(
  "Command: rpush bigboxlist B I G B O X C O D E B I O | Result: " +
    commandResult
);

/**
 * Check list
 * Command: lrange bigboxlist 0 -1
 * Result:
 *         1) "B"  2) "I"  3) "G"  4) "B"  5) "O"  6) "X"  7) "C"  8) "O"  9) "D"  10) "E"  11) "B"  12) "I"  13) "O"
 */
commandResult = await redisClient.lRange("bigboxlist", 0, -1);

console.log("Command: lrange bigboxlist 0 -1 | Result: ", commandResult);

/**
 * Trim items outside of index 3 to the end
 * Command: ltrim bigboxlist 3 -1
 * Result: OK
 */
commandResult = await redisClient.lTrim("bigboxlist", 3, -1);

console.log("Command: ltrim bigboxlist 3 -1 | Result: " + commandResult);

/**
 * Check list. Initial 3 items are deleted
 * Command: lrange bigboxlist 0 -1
 * Result:
 *         1) "B"  2) "O"  3) "X"  4) "C"  5) "O"  6) "D"  7) "E"  8) "B"  9) "I"  10) "O"
 */
commandResult = await redisClient.lRange("bigboxlist", 0, -1);

console.log("Command: lrange bigboxlist 0 -1 | Result: ", commandResult);

/**
 * Keep items from index 0 to 6 and delete others
 * Command: ltrim bigboxlist 0 6
 * Result: OK
 */
commandResult = await redisClient.lTrim("bigboxlist", 0, 6);

console.log("Command: ltrim bigboxlist 0 6 | Result: " + commandResult);

/**
 * Check list
 * Command: lrange bigboxlist 0 -1
 * Result:
 *         1) "B"  2) "O"  3) "X"  4) "C"  5) "O"  6) "D"  7) "E"
 */
commandResult = await redisClient.lRange("bigboxlist", 0, -1);

console.log("Command: lrange bigboxlist 0 -1 | Result: ", commandResult);

/**
 * Try to trim by keeping items from index 3 to 100
 * Max index in existing list is 6. So it will use 6 instead of 100
 * Command: ltrim bigboxlist 3 100
 * Result: OK
 */
commandResult = await redisClient.lTrim("bigboxlist", 3, 100);

console.log("Command: ltrim bigboxlist 3 100 | Result: " + commandResult);

/**
 * Check list
 * Command: lrange bigboxlist 0 -1
 * Result:
 *         1) "C"  2) "O"  3) "D"  4) "E"
 */
commandResult = await redisClient.lRange("bigboxlist", 0, -1);

console.log("Command: lrange bigboxlist 0 -1 | Result: ", commandResult);

/**
 * Provide ltrim indexes where start index is larger
 * This will empty the list
 * Command: ltrim bigboxlist 2 1
 * Result: OK
 */
commandResult = await redisClient.lTrim("bigboxlist", 2, 1);

console.log("Command: ltrim bigboxlist 2 1 | Result: " + commandResult);

/**
 * Check list, the list is empty now
 * Command: lrange bigboxlist 0 -1
 * Result: (empty array)
 */
commandResult = await redisClient.lRange("bigboxlist", 0, -1);

console.log("Command: lrange bigboxlist 0 -1 | Result: ", commandResult);

/**
 * Try to trim a list that does not exist
 * It will return OK
 * Command: ltrim nonexistinglist 0 1
 * Result: OK
 */
commandResult = await redisClient.lTrim("bigboxlist", 0, 1);

console.log("Command: ltrim nonexistinglist 0 1 | Result: " + commandResult);

/**
 * Set a string
 * Command: set bigboxstr "Some string for test"
 * Result: OK
 */
commandResult = await redisClient.set("bigboxstr", "Some string for test");

console.log(
  'Command: set bigboxstr "Some string for test" | Result: ' + commandResult
);

/**
 * Try to use LTRIM on a string
 * we get an error
 * Command: ltrim bigboxstr 0 1
 * Result: (error) WRONGTYPE Operation against a key holding the wrong kind of value
 */
try {
  commandResult = await redisClient.lTrim("bigboxstr", 0, 1);

  console.log("Command: ltrim bigboxstr 0 1 | Result: " + commandResult);
} catch (err) {
  console.log("Command: ltrim bigboxstr 0 1 | Error: ", err);
}

process.exit(0);

Output:

Command: rpush bigboxlist B I G B O X C O D E B I O | Result: 13
Command: lrange bigboxlist 0 -1 | Result:  [
  'B', 'I', 'G', 'B',
  'O', 'X', 'C', 'O',
  'D', 'E', 'B', 'I',
  'O'
]

Command: ltrim bigboxlist 3 -1 | Result: OK
Command: lrange bigboxlist 0 -1 | Result:  [
  'B', 'O', 'X', 'C',
  'O', 'D', 'E', 'B',
  'I', 'O'
]

Command: ltrim bigboxlist 0 6 | Result: OK
Command: lrange bigboxlist 0 -1 | Result:  [
  'B', 'O', 'X',
  'C', 'O', 'D',
  'E'
]

Command: ltrim bigboxlist 3 100 | Result: OK
Command: lrange bigboxlist 0 -1 | Result:  [ 'C', 'O', 'D', 'E' ]

Command: ltrim bigboxlist 2 1 | Result: OK
Command: lrange bigboxlist 0 -1 | Result:  []

Command: ltrim nonexistinglist 0 1 | Result: OK

Command: set bigboxstr "Some string for test" | Result: OK
Command: ltrim bigboxstr 0 1 | Error:  [ErrorReply: WRONGTYPE Operation against a key holding the wrong kind of value]

Notes

  • Use the function “lTrim” from the package node-redis.
  • Signature of the method is-
    lTrim(key: RedisCommandArgument, start: number, stop: number)
// Redis LTRIM Command example in Java

import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;

import java.util.List;

public class Ltrim {
    public static void main(String[] args) {
        // Create connection pool
        JedisPool jedisPool = new JedisPool("localhost", 6379);

        try (Jedis jedis = jedisPool.getResource()) {

            /**
             * Push items and create list
             * Command: rpush bigboxlist B I G B O X C O D E B I O
             * Result: (integer) 13
             */
            long rpushResult = jedis.rpush("bigboxlist", "B", "I", "G", "B", "O", "X", "C", "O", "D", "E", "B", "I", "O");

            System.out.println("Command: rpush bigboxlist B I G B O X C O D E B I O | Result: " + rpushResult);

            /**
             * Check list
             * Command: lrange bigboxlist 0 -1
             * Result:
             *         1) "B"  2) "I"  3) "G"  4) "B"  5) "O"  6) "X"  7) "C"  8) "O"  9) "D"  10) "E"  11) "B"  12) "I"  13) "O"
             */
            List<String> lrangeResult = jedis.lrange("bigboxlist", 0, -1);

            System.out.println("Command: lrange bigboxlist 0 -1 | Result: " + lrangeResult.toString());

            /**
             * Trim items outside of index 3 to the end
             * Command: ltrim bigboxlist 3 -1
             * Result: OK
             */
            String ltrimResult = jedis.ltrim("bigboxlist", 3, -1);

            System.out.println("Command: ltrim bigboxlist 3 -1 | Result: " + ltrimResult);

            /**
             * Check list. Initial 3 items are deleted
             * Command: lrange bigboxlist 0 -1
             * Result:
             *         1) "B"  2) "O"  3) "X"  4) "C"  5) "O"  6) "D"  7) "E"  8) "B"  9) "I"  10) "O"
             */
            lrangeResult = jedis.lrange("bigboxlist", 0, -1);

            System.out.println("Command: lrange bigboxlist 0 -1 | Result: " + lrangeResult.toString());

            /**
             * Keep items from index 0 to 6 and delete others
             * Command: ltrim bigboxlist 0 6
             * Result: OK
             */
            ltrimResult = jedis.ltrim("bigboxlist", 0, 6);

            System.out.println("Command: ltrim bigboxlist 0 6 | Result: " + ltrimResult);

            /**
             * Check list
             * Command: lrange bigboxlist 0 -1
             * Result:
             *         1) "B"  2) "O"  3) "X"  4) "C"  5) "O"  6) "D"  7) "E"
             */
            lrangeResult = jedis.lrange("bigboxlist", 0, -1);

            System.out.println("Command: lrange bigboxlist 0 -1 | Result: " + lrangeResult.toString());

            /**
             * Try to trim by keeping items from index 3 to 100
             * Max index in existing list is 6. So it will use 6 instead of 100
             * Command: ltrim bigboxlist 3 100
             * Result: OK
             */
            ltrimResult = jedis.ltrim("bigboxlist", 3, 100);

            System.out.println("Command: ltrim bigboxlist 3 100 | Result: " + ltrimResult);

            /**
             * Check list
             * Command: lrange bigboxlist 0 -1
             * Result:
             *         1) "C"  2) "O"  3) "D"  4) "E"
             */
            lrangeResult = jedis.lrange("bigboxlist", 0, -1);

            System.out.println("Command: lrange bigboxlist 0 -1 | Result: " + lrangeResult.toString());

            /**
             * Provide ltrim indexes where start index is larger
             * This will empty the list
             * Command: ltrim bigboxlist 2 1
             * Result: OK
             */
            ltrimResult = jedis.ltrim("bigboxlist", 2, 1);

            System.out.println("Command: ltrim bigboxlist 2 1 | Result: " + ltrimResult);

            /**
             * Check list, the list is empty now
             * Command: lrange bigboxlist 0 -1
             * Result: (empty array)
             */
            lrangeResult = jedis.lrange("bigboxlist", 0, -1);

            System.out.println("Command: lrange bigboxlist 0 -1 | Result: " + lrangeResult.toString());

            /**
             * Try to trim a list that does not exist
             * It will return OK
             * Command: ltrim nonexistinglist 0 1
             * Result: OK
             */
            ltrimResult = jedis.ltrim("bigboxlist", 0, 1);

            System.out.println("Command: ltrim nonexistinglist 0 1 | Result: " + ltrimResult);

            /**
             * Set a string
             * Command: set bigboxstr "Some string for test"
             * Result: OK
             */
            String setResult = jedis.set("bigboxstr", "Some string for test");

            System.out.println("Command: set bigboxstr "Some string for test" | Result: " + setResult);

            /**
             * Try to use LTRIM on a string
             * we get an error
             * Command: ltrim bigboxstr 0 1
             * Result: (error) WRONGTYPE Operation against a key holding the wrong kind of value
             */
            try {
                ltrimResult = jedis.ltrim("bigboxstr", 0, 1);

                System.out.println("Command: ltrim bigboxstr 0 1 | Result: " + ltrimResult);
            } catch(Exception e) {
                System.out.println("Command: ltrim bigboxstr 0 1 | Error: " + e.getMessage());
            }

        }

        jedisPool.close();
    }
}

Output:

Command: rpush bigboxlist B I G B O X C O D E B I O | Result: 13
Command: lrange bigboxlist 0 -1 | Result: [B, I, G, B, O, X, C, O, D, E, B, I, O]

Command: ltrim bigboxlist 3 -1 | Result: OK
Command: lrange bigboxlist 0 -1 | Result: [B, O, X, C, O, D, E, B, I, O]

Command: ltrim bigboxlist 0 6 | Result: OK
Command: lrange bigboxlist 0 -1 | Result: [B, O, X, C, O, D, E]

Command: ltrim bigboxlist 3 100 | Result: OK
Command: lrange bigboxlist 0 -1 | Result: [C, O, D, E]

Command: ltrim bigboxlist 2 1 | Result: OK
Command: lrange bigboxlist 0 -1 | Result: []

Command: ltrim nonexistinglist 0 1 | Result: OK

Command: set bigboxstr "Some string for test" | Result: OK
Command: ltrim bigboxstr 0 1 | Error: WRONGTYPE Operation against a key holding the wrong kind of value

Notes

  • Use method “ltrim” from Jedis package.
  • Signature of the method is-
    public String ltrim(final String key, final long start, final long stop)
// Redis LTRIM command examples in C#

using StackExchange.Redis;

namespace Ltrim
{
    internal class Program
    {
        static void Main(string[] args)
        {
            ConnectionMultiplexer redis = ConnectionMultiplexer.Connect("localhost");
            IDatabase rdb = redis.GetDatabase();

            /**
             * Push items and create list
             * Command: rpush bigboxlist B I G B O X C O D E B I O
             * Result: (integer) 13
             */
            long rpushResult = rdb.ListRightPush("bigboxlist", new RedisValue[] { "B", "I", "G", "B", "O", "X", "C", "O", "D", "E", "B", "I", "O" });

            Console.WriteLine("Command: rpush bigboxlist B I G B O X C O D E B I O | Result: " + rpushResult);

            /**
             * Check list
             * Command: lrange bigboxlist 0 -1
             * Result:
             *         1) "B"  2) "I"  3) "G"  4) "B"  5) "O"  6) "X"  7) "C"  8) "O"  9) "D"  10) "E"  11) "B"  12) "I"  13) "O"
             */
            RedisValue[] lrangeResult = rdb.ListRange("bigboxlist", 0, -1);

            Console.WriteLine("Command: lrange bigboxlist 0 -1 | Result: " + string.Join(", ", lrangeResult));

            /**
             * Trim items outside of index 3 to the end
             * Command: ltrim bigboxlist 3 -1
             * Result: OK
             */
             rdb.ListTrim("bigboxlist", 3, -1);

            Console.WriteLine("Command: ltrim bigboxlist 3 -1");

            /**
             * Check list. Initial 3 items are deleted
             * Command: lrange bigboxlist 0 -1
             * Result:
             *         1) "B"  2) "O"  3) "X"  4) "C"  5) "O"  6) "D"  7) "E"  8) "B"  9) "I"  10) "O"
             */
            lrangeResult = rdb.ListRange("bigboxlist", 0, -1);

            Console.WriteLine("Command: lrange bigboxlist 0 -1 | Result: " + string.Join(", ", lrangeResult));

            /**
             * Keep items from index 0 to 6 and delete others
             * Command: ltrim bigboxlist 0 6
             * Result: OK
             */
            rdb.ListTrim("bigboxlist", 0, 6);

            Console.WriteLine("Command: ltrim bigboxlist 0 6");

            /**
             * Check list
             * Command: lrange bigboxlist 0 -1
             * Result:
             *         1) "B"  2) "O"  3) "X"  4) "C"  5) "O"  6) "D"  7) "E"
             */
            lrangeResult = rdb.ListRange("bigboxlist", 0, -1);

            Console.WriteLine("Command: lrange bigboxlist 0 -1 | Result: " + string.Join(", ", lrangeResult));

            /**
             * Try to trim by keeping items from index 3 to 100
             * Max index in existing list is 6. So it will use 6 instead of 100
             * Command: ltrim bigboxlist 3 100
             * Result: OK
             */
            rdb.ListTrim("bigboxlist", 3, 100);

            Console.WriteLine("Command: ltrim bigboxlist 3 100");

            /**
             * Check list
             * Command: lrange bigboxlist 0 -1
             * Result:
             *         1) "C"  2) "O"  3) "D"  4) "E"
             */
            lrangeResult = rdb.ListRange("bigboxlist", 0, -1);

            Console.WriteLine("Command: lrange bigboxlist 0 -1 | Result: " + string.Join(", ", lrangeResult));

            /**
             * Provide ltrim indexes where start index is larger
             * This will empty the list
             * Command: ltrim bigboxlist 2 1
             * Result: OK
             */
            rdb.ListTrim("bigboxlist", 2, 1);

            Console.WriteLine("Command: ltrim bigboxlist 2 1");

            /**
             * Check list, the list is empty now
             * Command: lrange bigboxlist 0 -1
             * Result: (empty array)
             */
            lrangeResult = rdb.ListRange("bigboxlist", 0, -1);

            Console.WriteLine("Command: lrange bigboxlist 0 -1 | Result: " + string.Join(", ", lrangeResult));

            /**
             * Try to trim a list that does not exist
             * It will return OK
             * Command: ltrim nonexistinglist 0 1
             * Result: OK
             */
            rdb.ListTrim("bigboxlist", 0, 1);

            Console.WriteLine("Command: ltrim nonexistinglist 0 1");

            /**
             * Set a string
             * Command: set bigboxstr "Some string for test"
             * Result: OK
             */
            bool setResult = rdb.StringSet("bigboxstr", "Some string for test");

            Console.WriteLine("Command: set bigboxstr "Some string for test" | Result: " + setResult);

            /**
             * Try to use LTRIM on a string
             * we get an error
             * Command: ltrim bigboxstr 0 1
             * Result: (error) WRONGTYPE Operation against a key holding the wrong kind of value
             */
            try
            {
                rdb.ListTrim("bigboxstr", 0, 1);

                Console.WriteLine("Command: ltrim bigboxstr 0 1");
            }
            catch (Exception e)
            {
                Console.WriteLine("Command: ltrim bigboxstr 0 1 | Error: " + e.Message);
            }
        }
    }
}

Output:

Command: rpush bigboxlist B I G B O X C O D E B I O | Result: 13
Command: lrange bigboxlist 0 -1 | Result: B, I, G, B, O, X, C, O, D, E, B, I, O

Command: ltrim bigboxlist 3 -1
Command: lrange bigboxlist 0 -1 | Result: B, O, X, C, O, D, E, B, I, O

Command: ltrim bigboxlist 0 6
Command: lrange bigboxlist 0 -1 | Result: B, O, X, C, O, D, E

Command: ltrim bigboxlist 3 100
Command: lrange bigboxlist 0 -1 | Result: C, O, D, E

Command: ltrim bigboxlist 2 1
Command: lrange bigboxlist 0 -1 | Result:

Command: ltrim nonexistinglist 0 1

Command: set bigboxstr "Some string for test" | Result: True
Command: ltrim bigboxstr 0 1 | Error: WRONGTYPE Operation against a key holding the wrong kind of value

Notes

  • Use the method “ListTrim” from StackExchange.Redis.
  • Signature of the method is-
    void ListTrim(RedisKey key, long start, long stop, CommandFlags flags = CommandFlags.None)
<?php
// Redis LTRIM command example in PHP

require 'vendor/autoload.php';

// Connect to Redis
$redisClient = new PredisClient([
    'scheme' => 'tcp',
    'host' => 'localhost',
    'port' => 6379,
]);


/**
 * Push items and create list
 * Command: rpush bigboxlist B I G B O X C O D E B I O
 * Result: (integer) 13
 */
$commandResult = $redisClient->rpush("bigboxlist", ["B", "I", "G", "B", "O", "X", "C", "O", "D", "E", "B", "I", "O"]);

echo "Command: rpush bigboxlist B I G B O X C O D E B I O | Result: " . $commandResult . "n";

/**
 * Check list
 * Command: lrange bigboxlist 0 -1
 * Result:
 *         1) "B"  2) "I"  3) "G"  4) "B"  5) "O"  6) "X"  7) "C"  8) "O"  9) "D"  10) "E"  11) "B"  12) "I"  13) "O"
 */
$commandResult = $redisClient->lrange("bigboxlist", 0, -1);

echo "Command: lrange bigboxlist 0 -1 | Result: ";
print_r($commandResult);

/**
 * Trim items outside of index 3 to the end
 * Command: ltrim bigboxlist 3 -1
 * Result: OK
 */
$commandResult = $redisClient->ltrim("bigboxlist", 3, -1);

echo "Command: ltrim bigboxlist 3 -1 | Result: " . $commandResult . "n";

/**
 * Check list. Initial 3 items are deleted
 * Command: lrange bigboxlist 0 -1
 * Result:
 *         1) "B"  2) "O"  3) "X"  4) "C"  5) "O"  6) "D"  7) "E"  8) "B"  9) "I"  10) "O"
 */
$commandResult = $redisClient->lrange("bigboxlist", 0, -1);

echo "Command: lrange bigboxlist 0 -1 | Result: ";
print_r($commandResult);

/**
 * Keep items from index 0 to 6 and delete others
 * Command: ltrim bigboxlist 0 6
 * Result: OK
 */
$commandResult = $redisClient->ltrim("bigboxlist", 0, 6);

echo "Command: ltrim bigboxlist 0 6 | Result: " . $commandResult . "n";

/**
 * Check list
 * Command: lrange bigboxlist 0 -1
 * Result:
 *         1) "B"  2) "O"  3) "X"  4) "C"  5) "O"  6) "D"  7) "E"
 */
$commandResult = $redisClient->lrange("bigboxlist", 0, -1);

echo "Command: lrange bigboxlist 0 -1 | Result: ";
print_r($commandResult);

/**
 * Try to trim by keeping items from index 3 to 100
 * Max index in existing list is 6. So it will use 6 instead of 100
 * Command: ltrim bigboxlist 3 100
 * Result: OK
 */
$commandResult = $redisClient->ltrim("bigboxlist", 3, 100);

echo "Command: ltrim bigboxlist 3 100 | Result: " . $commandResult . "n";

/**
 * Check list
 * Command: lrange bigboxlist 0 -1
 * Result:
 *         1) "C"  2) "O"  3) "D"  4) "E"
 */
$commandResult = $redisClient->lrange("bigboxlist", 0, -1);

echo "Command: lrange bigboxlist 0 -1 | Result: ";
print_r($commandResult);

/**
 * Provide ltrim indexes where start index is larger
 * This will empty the list
 * Command: ltrim bigboxlist 2 1
 * Result: OK
 */
$commandResult = $redisClient->ltrim("bigboxlist", 2, 1);

echo "Command: ltrim bigboxlist 2 1 | Result: " . $commandResult . "n";

/**
 * Check list, the list is empty now
 * Command: lrange bigboxlist 0 -1
 * Result: (empty array)
 */
$commandResult = $redisClient->lrange("bigboxlist", 0, -1);

echo "Command: lrange bigboxlist 0 -1 | Result: ";
print_r($commandResult);

/**
 * Try to trim a list that does not exist
 * It will return OK
 * Command: ltrim nonexistinglist 0 1
 * Result: OK
 */
$commandResult = $redisClient->ltrim("bigboxlist", 0, 1);

echo "Command: ltrim nonexistinglist 0 1 | Result: " . $commandResult . "n";

/**
 * Set a string
 * Command: set bigboxstr "Some string for test"
 * Result: OK
 */
$commandResult = $redisClient->set("bigboxstr", "Some string for test");

echo "Command: set bigboxstr "Some string for test" | Result: " . $commandResult . "n";

/**
 * Try to use LTRIM on a string
 * we get an error
 * Command: ltrim bigboxstr 0 1
 * Result: (error) WRONGTYPE Operation against a key holding the wrong kind of value
 */
try {
    $commandResult = $redisClient->ltrim("bigboxstr", 0, 1);

    echo "Command: ltrim bigboxstr 0 1 | Result: " . $commandResult . "n";
} catch(Exception $e) {
    echo "Command: ltrim bigboxstr 0 1 | Error: " . $e->getMessage() . "n";
}

Output:

Command: rpush bigboxlist B I G B O X C O D E B I O | Result: 13
Command: lrange bigboxlist 0 -1 | Result: Array
(
    [0] => B
    [1] => I
    [2] => G
    [3] => B
    [4] => O
    [5] => X
    [6] => C
    [7] => O
    [8] => D
    [9] => E
    [10] => B
    [11] => I
    [12] => O
)

Command: ltrim bigboxlist 3 -1 | Result: OK
Command: lrange bigboxlist 0 -1 | Result: Array
(
    [0] => B
    [1] => O
    [2] => X
    [3] => C
    [4] => O
    [5] => D
    [6] => E
    [7] => B
    [8] => I
    [9] => O
)

Command: ltrim bigboxlist 0 6 | Result: OK
Command: lrange bigboxlist 0 -1 | Result: Array
(
    [0] => B
    [1] => O
    [2] => X
    [3] => C
    [4] => O
    [5] => D
    [6] => E
)

Command: ltrim bigboxlist 3 100 | Result: OK
Command: lrange bigboxlist 0 -1 | Result: Array
(
    [0] => C
    [1] => O
    [2] => D
    [3] => E
)

Command: ltrim bigboxlist 2 1 | Result: OK
Command: lrange bigboxlist 0 -1 | Result: Array
(
)

Command: ltrim nonexistinglist 0 1 | Result: OK

Command: set bigboxstr "Some string for test" | Result: OK
Command: ltrim bigboxstr 0 1 | Error: WRONGTYPE Operation against a key holding the wrong kind of value

Notes

  • Use the method “ltrim” of predis.
  • Signature of the method is-
    ltrim(string $key, int $start, int $stop): mixed
# Redis LTRIM command example in Python

import redis
import time

# Create Redis client
redisClient = redis.Redis(host='localhost', port=6379,
                          username='default', password='',
                          decode_responses=True)


# Push items and create list
# Command: rpush bigboxlist B I G B O X C O D E B I O
# Result: (integer) 13
commandResult = redisClient.rpush("bigboxlist", "B", "I", "G", "B", "O", "X", "C", "O", "D", "E", "B", "I", "O")

print("Command: rpush bigboxlist B I G B O X C O D E B I O | Result: {}".format(commandResult))

# Check list
# Command: lrange bigboxlist 0 -1
# Result:
#         1) "B"  2) "I"  3) "G"  4) "B"  5) "O"  6) "X"  7) "C"  8) "O"  9) "D"  10) "E"  11) "B"  12) "I"  13) "O"
commandResult = redisClient.lrange("bigboxlist", 0, -1)

print("Command: lrange bigboxlist 0 -1 | Result: {}".format(commandResult))

# Trim items outside of index 3 to the end
# Command: ltrim bigboxlist 3 -1
# Result: OK
commandResult = redisClient.ltrim("bigboxlist", 3, -1)

print("Command: ltrim bigboxlist 3 -1 | Result: {}".format(commandResult))

# Check list. Initial 3 items are deleted
# Command: lrange bigboxlist 0 -1
# Result:
#         1) "B"  2) "O"  3) "X"  4) "C"  5) "O"  6) "D"  7) "E"  8) "B"  9) "I"  10) "O"
commandResult = redisClient.lrange("bigboxlist", 0, -1)

print("Command: lrange bigboxlist 0 -1 | Result: {}".format(commandResult))

# Keep items from index 0 to 6 and delete others
# Command: ltrim bigboxlist 0 6
# Result: OK
commandResult = redisClient.ltrim("bigboxlist", 0, 6)

print("Command: ltrim bigboxlist 0 6 | Result: {}".format(commandResult))

# Check list
# Command: lrange bigboxlist 0 -1
# Result:
#         1) "B"  2) "O"  3) "X"  4) "C"  5) "O"  6) "D"  7) "E"
commandResult = redisClient.lrange("bigboxlist", 0, -1)

print("Command: lrange bigboxlist 0 -1 | Result: {}".format(commandResult))

# Try to trim by keeping items from index 3 to 100
# Max index in existing list is 6. So it will use 6 instead of 100
# Command: ltrim bigboxlist 3 100
# Result: OK
commandResult = redisClient.ltrim("bigboxlist", 3, 100)

print("Command: ltrim bigboxlist 3 100 | Result: {}".format(commandResult))

# Check list
# Command: lrange bigboxlist 0 -1
# Result:
#         1) "C"  2) "O"  3) "D"  4) "E"
commandResult = redisClient.lrange("bigboxlist", 0, -1)

print("Command: lrange bigboxlist 0 -1 | Result: {}".format(commandResult))

# Provide ltrim indexes where start index is larger
# This will empty the list
# Command: ltrim bigboxlist 2 1
# Result: OK
commandResult = redisClient.ltrim("bigboxlist", 2, 1)

print("Command: ltrim bigboxlist 2 1 | Result: {}".format(commandResult))

# Check list, the list is empty now
# Command: lrange bigboxlist 0 -1
# Result: (empty array)
commandResult = redisClient.lrange("bigboxlist", 0, -1)

print("Command: lrange bigboxlist 0 -1 | Result: {}".format(commandResult))

# Try to trim a list that does not exist
# It will return OK
# Command: ltrim nonexistinglist 0 1
# Result: OK
commandResult = redisClient.ltrim("bigboxlist", 0, 1)

print("Command: ltrim nonexistinglist 0 1 | Result: {}".format(commandResult))

# Set a string
# Command: set bigboxstr "Some string for test"
# Result: OK
commandResult = redisClient.set("bigboxstr", "Some string for test")

print("Command: set bigboxstr "Some string for test" | Result: {}".format(commandResult))

# Try to use LTRIM on a string
# we get an error
# Command: ltrim bigboxstr 0 1
# Result: (error) WRONGTYPE Operation against a key holding the wrong kind of value
try:
    commandResult = redisClient.ltrim("bigboxstr", 0, 1)

    print("Command: ltrim bigboxstr 0 1 | Result: {}".format(commandResult))
except Exception as error:
    print("Command: ltrim bigboxstr 0 1 | Error: ", error)

Output:

Command: rpush bigboxlist B I G B O X C O D E B I O | Result: 13
Command: lrange bigboxlist 0 -1 | Result: ['B', 'I', 'G', 'B', 'O', 'X', 'C', 'O', 'D', 'E', 'B', 'I', 'O']

Command: ltrim bigboxlist 3 -1 | Result: True
Command: lrange bigboxlist 0 -1 | Result: ['B', 'O', 'X', 'C', 'O', 'D', 'E', 'B', 'I', 'O']

Command: ltrim bigboxlist 0 6 | Result: True
Command: lrange bigboxlist 0 -1 | Result: ['B', 'O', 'X', 'C', 'O', 'D', 'E']

Command: ltrim bigboxlist 3 100 | Result: True
Command: lrange bigboxlist 0 -1 | Result: ['C', 'O', 'D', 'E']

Command: ltrim bigboxlist 2 1 | Result: True
Command: lrange bigboxlist 0 -1 | Result: []

Command: ltrim nonexistinglist 0 1 | Result: True

Command: set bigboxstr "Some string for test" | Result: True
Command: ltrim bigboxstr 0 1 | Error:  WRONGTYPE Operation against a key holding the wrong kind of value

Notes

  • Use method “ltrim” from redis-py.
  • Signature of the method is –
    def ltrim(self, name: str, start: int, end: int) -> Union[Awaitable[str], str]
# Redis LTRIM command example in Ruby

require 'redis'

redis = Redis.new(host: "localhost", port: 6379)

# Push items and create list
# Command: rpush bigboxlist B I G B O X C O D E B I O
# Result: (integer) 13
commandResult = redis.rpush("bigboxlist", ["B", "I", "G", "B", "O", "X", "C", "O", "D", "E", "B", "I", "O"])

print("Command: rpush bigboxlist B I G B O X C O D E B I O | Result: ", commandResult, "n")

# Check list
# Command: lrange bigboxlist 0 -1
# Result:
#         1) "B"  2) "I"  3) "G"  4) "B"  5) "O"  6) "X"  7) "C"  8) "O"  9) "D"  10) "E"  11) "B"  12) "I"  13) "O"
commandResult = redis.lrange("bigboxlist", 0, -1)

print("Command: lrange bigboxlist 0 -1 | Result: ", commandResult, "n")

# Trim items outside of index 3 to the end
# Command: ltrim bigboxlist 3 -1
# Result: OK
commandResult = redis.ltrim("bigboxlist", 3, -1)

print("Command: ltrim bigboxlist 3 -1 | Result: ", commandResult, "n")

# Check list. Initial 3 items are deleted
# Command: lrange bigboxlist 0 -1
# Result:
#         1) "B"  2) "O"  3) "X"  4) "C"  5) "O"  6) "D"  7) "E"  8) "B"  9) "I"  10) "O"
commandResult = redis.lrange("bigboxlist", 0, -1)

print("Command: lrange bigboxlist 0 -1 | Result: ", commandResult, "n")

# Keep items from index 0 to 6 and delete others
# Command: ltrim bigboxlist 0 6
# Result: OK
commandResult = redis.ltrim("bigboxlist", 0, 6)

print("Command: ltrim bigboxlist 0 6 | Result: ", commandResult, "n")

# Check list
# Command: lrange bigboxlist 0 -1
# Result:
#         1) "B"  2) "O"  3) "X"  4) "C"  5) "O"  6) "D"  7) "E"
commandResult = redis.lrange("bigboxlist", 0, -1)

print("Command: lrange bigboxlist 0 -1 | Result: ", commandResult, "n")

# Try to trim by keeping items from index 3 to 100
# Max index in existing list is 6. So it will use 6 instead of 100
# Command: ltrim bigboxlist 3 100
# Result: OK
commandResult = redis.ltrim("bigboxlist", 3, 100)

print("Command: ltrim bigboxlist 3 100 | Result: ", commandResult, "n")

# Check list
# Command: lrange bigboxlist 0 -1
# Result:
#         1) "C"  2) "O"  3) "D"  4) "E"
commandResult = redis.lrange("bigboxlist", 0, -1)

print("Command: lrange bigboxlist 0 -1 | Result: ", commandResult, "n")

# Provide ltrim indexes where start index is larger
# This will empty the list
# Command: ltrim bigboxlist 2 1
# Result: OK
commandResult = redis.ltrim("bigboxlist", 2, 1)

print("Command: ltrim bigboxlist 2 1 | Result: ", commandResult, "n")

# Check list, the list is empty now
# Command: lrange bigboxlist 0 -1
# Result: (empty array)
commandResult = redis.lrange("bigboxlist", 0, -1)

print("Command: lrange bigboxlist 0 -1 | Result: ", commandResult, "n")

# Try to trim a list that does not exist
# It will return OK
# Command: ltrim nonexistinglist 0 1
# Result: OK
commandResult = redis.ltrim("bigboxlist", 0, 1)

print("Command: ltrim nonexistinglist 0 1 | Result: ", commandResult, "n")

# Set a string
# Command: set bigboxstr "Some string for test"
# Result: OK
commandResult = redis.set("bigboxstr", "Some string for test")

print("Command: set bigboxstr "Some string for test" | Result: ", commandResult, "n")

# Try to use LTRIM on a string
# we get an error
# Command: ltrim bigboxstr 0 1
# Result: (error) WRONGTYPE Operation against a key holding the wrong kind of value
begin
    commandResult = redis.ltrim("bigboxstr", 0, 1)

    print("Command: ltrim bigboxstr 0 1 | Result: ", commandResult, "n")
rescue => e
    print("Command: ltrim bigboxstr 0 1 | Error: ", e, "n")
end

Output:

Command: rpush bigboxlist B I G B O X C O D E B I O | Result: 13
Command: lrange bigboxlist 0 -1 | Result: ["B", "I", "G", "B", "O", "X", "C", "O", "D", "E", "B", "I", "O"]

Command: ltrim bigboxlist 3 -1 | Result: OK
Command: lrange bigboxlist 0 -1 | Result: ["B", "O", "X", "C", "O", "D", "E", "B", "I", "O"]

Command: ltrim bigboxlist 0 6 | Result: OK
Command: lrange bigboxlist 0 -1 | Result: ["B", "O", "X", "C", "O", "D", "E"]

Command: ltrim bigboxlist 3 100 | Result: OK
Command: lrange bigboxlist 0 -1 | Result: ["C", "O", "D", "E"]

Command: ltrim bigboxlist 2 1 | Result: OK
Command: lrange bigboxlist 0 -1 | Result: []

Command: ltrim nonexistinglist 0 1 | Result: OK

Command: set bigboxstr "Some string for test" | Result: OK
Command: ltrim bigboxstr 0 1 | Error: WRONGTYPE Operation against a key holding the wrong kind of value

Notes

  • Use method “ltrim” from the redis-rb.
  • Signature of the method is-

    # @param [String] key
    # @param [Integer] start start index
    # @param [Integer] stop stop index
    # @return [String] `OK`

    def ltrim(key, start, stop)

Source Code

Use the following links to get the source code used in this article-

Source Code ofSource Code Link
Command Examples GitHub
Golang Implementation GitHub
NodeJS Implementation GitHub
Java Implementation GitHub
C# Implementation GitHub
PHP Implementation GitHub
Python Implementation GitHub
Ruby Implementation GitHub

Related Commands

CommandDetails
LPUSH Command Details
LRANGE Command Details

Leave a Comment


The reCAPTCHA verification period has expired. Please reload the page.