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String commands operate on key-value pairs where the value is a byte string. Kora supports all standard Redis string operations with identical semantics.

​
GET

Get the value of a key. Syntax 
GET key
​
key
string
required
The key to retrieve
Return value
​
value
string | null
The value stored at the key, or null if the key does not exist
Examples 
redis-cli> SET mykey "Hello"
OK
redis-cli> GET mykey
"Hello"
redis-cli> GET nonexistent
(nil)
Time complexity: O(1)

​
SET

Set the value of a key with optional expiration and conditional flags. Syntax 
SET key value [EX seconds] [PX milliseconds] [NX|XX]
​
key
string
required
The key to set
​
value
string
required
The value to store
​
EX
integer
Set the key’s time to live in seconds
​
PX
integer
Set the key’s time to live in milliseconds
​
NX
flag
Only set the key if it does not already exist
​
XX
flag
Only set the key if it already exists
Return value
​
result
string | null
OK if SET was executed correctly, or null if the SET operation was not performed due to NX or XX conditions
Examples 
redis-cli> SET mykey "Hello"
OK
redis-cli> SET mykey "World" EX 10
OK
redis-cli> SET newkey "value" NX
OK
redis-cli> SET newkey "value2" NX
(nil)
Time complexity: O(1)

​
APPEND

Append a value to a key. Syntax 
APPEND key value
​
key
string
required
The key to append to
​
value
string
required
The value to append
Return value
​
length
integer
The length of the string after the append operation
Examples 
redis-cli> SET mykey "Hello"
OK
redis-cli> APPEND mykey " World"
(integer) 11
redis-cli> GET mykey
"Hello World"
Time complexity: O(1)

​
STRLEN

Get the length of the value stored in a key. Syntax 
STRLEN key
​
key
string
required
The key to measure
Return value
​
length
integer
The length of the string, or 0 if the key does not exist
Examples 
redis-cli> SET mykey "Hello World"
OK
redis-cli> STRLEN mykey
(integer) 11
redis-cli> STRLEN nonexistent
(integer) 0
Time complexity: O(1)

​
INCR

Increment the integer value of a key by one. Syntax 
INCR key
​
key
string
required
The key containing an integer value
Return value
​
value
integer
The value of the key after incrementing
Examples 
redis-cli> SET counter "10"
OK
redis-cli> INCR counter
(integer) 11
redis-cli> INCR counter
(integer) 12
redis-cli> INCR newcounter
(integer) 1
Time complexity: O(1)

​
DECR

Decrement the integer value of a key by one. Syntax 
DECR key
​
key
string
required
The key containing an integer value
Return value
​
value
integer
The value of the key after decrementing
Examples 
redis-cli> SET counter "10"
OK
redis-cli> DECR counter
(integer) 9
redis-cli> DECR counter
(integer) 8
Time complexity: O(1)

​
INCRBY

Increment the integer value of a key by a given amount. Syntax 
INCRBY key delta
​
key
string
required
The key containing an integer value
​
delta
integer
required
The amount to increment by
Return value
​
value
integer
The value of the key after incrementing
Examples 
redis-cli> SET counter "10"
OK
redis-cli> INCRBY counter 5
(integer) 15
redis-cli> INCRBY counter -3
(integer) 12
Time complexity: O(1)

​
DECRBY

Decrement the integer value of a key by a given amount. Syntax 
DECRBY key delta
​
key
string
required
The key containing an integer value
​
delta
integer
required
The amount to decrement by
Return value
​
value
integer
The value of the key after decrementing
Examples 
redis-cli> SET counter "10"
OK
redis-cli> DECRBY counter 3
(integer) 7
Time complexity: O(1)

​
INCRBYFLOAT

Increment the float value of a key by a given amount. Syntax 
INCRBYFLOAT key delta
​
key
string
required
The key containing a numeric value
​
delta
float
required
The amount to increment by
Return value
​
value
float
The value of the key after incrementing
Examples 
redis-cli> SET price "10.50"
OK
redis-cli> INCRBYFLOAT price 2.25
"12.75"
redis-cli> INCRBYFLOAT price -1.5
"11.25"
Time complexity: O(1)

​
MGET

Get the values of all given keys. Syntax 
MGET key [key ...]
​
key
string
required
One or more keys to retrieve
Return value
​
values
array
Array of values at the specified keys. For keys that do not exist, null is returned
Examples 
redis-cli> SET key1 "Hello"
OK
redis-cli> SET key2 "World"
OK
redis-cli> MGET key1 key2 nonexistent
1) "Hello"
2) "World"
3) (nil)
Time complexity: O(N) where N is the number of keys to retrieve

​
MSET

Set multiple keys to multiple values. Syntax 
MSET key value [key value ...]
​
key
string
required
A key to set
​
value
string
required
The value for the corresponding key
Return value
​
result
string
Always returns OK
Examples 
redis-cli> MSET key1 "Hello" key2 "World"
OK
redis-cli> GET key1
"Hello"
redis-cli> GET key2
"World"
Time complexity: O(N) where N is the number of keys to set

​
SETNX

Set the value of a key only if it does not exist. Syntax 
SETNX key value
​
key
string
required
The key to set
​
value
string
required
The value to store
Return value
​
result
integer
1 if the key was set, 0 if the key was not set
Examples 
redis-cli> SETNX mykey "Hello"
(integer) 1
redis-cli> SETNX mykey "World"
(integer) 0
redis-cli> GET mykey
"Hello"
Time complexity: O(1)

​
GETSET

Set the string value of a key and return its old value. Syntax 
GETSET key value
​
key
string
required
The key to set
​
value
string
required
The new value
Return value
​
old_value
string | null
The previous value stored at key, or null if the key did not exist
Examples 
redis-cli> SET mykey "Hello"
OK
redis-cli> GETSET mykey "World"
"Hello"
redis-cli> GET mykey
"World"
Time complexity: O(1) Note: GETSET is deprecated. Use SET with the GET option instead.

​
GETRANGE

Get a substring of the string stored at a key. Syntax 
GETRANGE key start end
​
key
string
required
The key containing the string
​
start
integer
required
The start offset (0-based, negative values count from the end)
​
end
integer
required
The end offset (inclusive, negative values count from the end)
Return value
​
substring
string
The substring of the value
Examples 
redis-cli> SET mykey "This is a string"
OK
redis-cli> GETRANGE mykey 0 3
"This"
redis-cli> GETRANGE mykey -3 -1
"ing"
redis-cli> GETRANGE mykey 0 -1
"This is a string"
Time complexity: O(N) where N is the length of the returned string

​
SETRANGE

Overwrite part of a string at a key starting at the specified offset. Syntax 
SETRANGE key offset value
​
key
string
required
The key to modify
​
offset
integer
required
The byte offset to start writing at
​
value
string
required
The value to write
Return value
​
length
integer
The length of the string after the modification
Examples 
redis-cli> SET key1 "Hello World"
OK
redis-cli> SETRANGE key1 6 "Kora"
(integer) 11
redis-cli> GET key1
"Hello Kora!"
Time complexity: O(1) not counting the time to copy the new string in place

​
GETDEL

Get the value of a key and delete the key. Syntax 
GETDEL key
​
key
string
required
The key to get and delete
Return value
​
value
string | null
The value of the key, or null if the key does not exist
Examples 
redis-cli> SET mykey "Hello"
OK
redis-cli> GETDEL mykey
"Hello"
redis-cli> GET mykey
(nil)
Time complexity: O(1)

​
GETEX

Get the value of a key and optionally set its expiration. Syntax 
GETEX key [EX seconds | PX milliseconds | EXAT timestamp | PXAT timestamp_ms | PERSIST]
​
key
string
required
The key to get
​
EX
integer
Set the key’s time to live in seconds
​
PX
integer
Set the key’s time to live in milliseconds
​
EXAT
integer
Set the key to expire at a Unix timestamp (seconds)
​
PXAT
integer
Set the key to expire at a Unix timestamp (milliseconds)
​
PERSIST
flag
Remove the time to live associated with the key
Return value
​
value
string | null
The value of the key, or null if the key does not exist
Examples 
redis-cli> SET mykey "Hello"
OK
redis-cli> GETEX mykey EX 60
"Hello"
redis-cli> TTL mykey
(integer) 60
Time complexity: O(1)

​
MSETNX

Set multiple keys to multiple values, only if none of the keys exist. Syntax 
MSETNX key value [key value ...]
​
key
string
required
A key to set
​
value
string
required
The value for the corresponding key
Return value
​
result
integer
1 if all keys were set, 0 if no key was set (at least one key already existed)
Examples 
redis-cli> MSETNX key1 "Hello" key2 "World"
(integer) 1
redis-cli> MSETNX key1 "foo" key3 "bar"
(integer) 0
redis-cli> MGET key1 key2 key3
1) "Hello"
2) "World"
3) (nil)
Time complexity: O(N) where N is the number of keys to set

​
Redis Compatibility

Kora implements all standard Redis string commands with identical semantics. Commands behave exactly as documented in the Redis specification.

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