String Operations

String Operations

Redis strings are binary-safe — they can contain any sequence of bytes. The maximum size is 512 MB.

MSET and MGET — Multiple Keys

Setting and getting multiple keys in a single round-trip:

MSET key1 val1 key2 val2 key3 val3
MGET key1 key2 key3

Output:

OK
1) "val1"
2) "val2"
3) "val3"

MGET returns (nil) for keys that don't exist.

APPEND — Concatenate

Append a value to an existing string. Returns the new length:

SET log "2024-01-01: "
APPEND log "server started"
GET log

Output:

OK
(integer) 26
"2024-01-01: server started"

If the key doesn't exist, APPEND creates it (like SET).

STRLEN — String Length

SET message "Hello"
STRLEN message

Output:

OK
(integer) 5

GETSET — Atomic Get-and-Set

Get the old value while setting a new one — useful for swapping:

SET counter "old"
GETSET counter "new"
GET counter

Output:

OK
"old"
"new"

SETNX — Set if Not Exists

Set a key only if it does not already exist. Returns 1 if set, 0 if skipped:

SETNX lock "process-1"
SETNX lock "process-2"
GET lock

Output:

(integer) 1
(integer) 0
"process-1"

SETNX is the basis for distributed locks in Redis.

Your Task

Use MSET to set three keys at once: name → "Redis", version → "7", language → "C". Then use MGET to retrieve all three.