String commands operate on the most basic ValKeyper data type: strings. A string value can be any sequence of bytes, up to 512 MB in length.
SET
Set the string value of a key. If the key already holds a value, it is overwritten.
Syntax
SET key value [PX milliseconds]
Parameters
Set the specified expire time, in milliseconds. When provided with the PX flag, the key will automatically be deleted after the specified duration.
Return Value
Simple string reply: OK if SET was executed correctly.
Examples
# Set a simple key-value pair
SET mykey "Hello"
# Response: OK
# Set a key with expiration (1000ms = 1 second)
SET tempkey "temporary value" PX 1000
# Response: OK
# After 1 second, the key will be automatically deleted
# Overwrite an existing key
SET mykey "New Value"
# Response: OK
Implementation Details
From store.go:209-220:
case "SET":
key := buff[1]
val := buff[2]
ex := -1
if len(buff) > 4 {
ex, err = strconv.Atoi(buff[4])
if err != nil {
panic(err)
}
}
kv.Set(key, val, ex)
res = []byte("+OK\r\n")
ex != -1), a goroutine is spawned to handle automatic key deletion after the specified duration.
GET
Get the string value of a key. If the key does not exist, the special value nil is returned.
Syntax
Parameters
Return Value
- Bulk string reply: The value of the key
- Null reply:
nil if the key does not exist
Examples
# Get an existing key
SET mykey "Hello"
GET mykey
# Response: "Hello"
# Get a non-existent key
GET nonexistent
# Response: (nil)
# Get a key that has expired
SET tempkey "value" PX 100
# Wait 200ms
GET tempkey
# Response: (nil)
Implementation Details
From store.go:221-228:
case "GET":
key := buff[1]
val, ok := kv.store[key]
if !ok {
res = []byte("$-1\r\n")
} else {
res = []byte(fmt.Sprintf("$%d\r\n%s\r\n", len(val), val))
}
ECHO
Returns the provided message. Useful for testing connectivity and verifying the server is responding.
Syntax
Parameters
Return Value
Bulk string reply: The provided message.
Examples
ECHO "Hello World"
# Response: "Hello World"
ECHO "Testing connection"
# Response: "Testing connection"
Implementation Details
From store.go:190-192:
case "ECHO":
msg := buff[1]
res = []byte(fmt.Sprintf("$%d\r\n%s\r\n", len(msg), msg))
INCR
Increments the integer value of a key by one. If the key does not exist, it is set to 0 before performing the operation.
Syntax
Parameters
Return Value
Integer reply: The value of the key after the increment.
Errors
- Returns an error if the key contains a value of the wrong type or contains a string that cannot be represented as an integer.
Examples
# Increment a non-existent key (initialized to 0)
INCR counter
# Response: 1
INCR counter
# Response: 2
INCR counter
# Response: 3
# Set an initial value
SET mycounter "10"
INCR mycounter
# Response: 11
# Error: non-integer value
SET mystring "hello"
INCR mystring
# Response: -ERR value is not an integer or out of range
Implementation Details
From store.go:507-521:
case "INCR":
v, ok := kv.store[buff[1]]
if !ok {
kv.store[buff[1]] = "1"
} else {
val, err := strconv.Atoi(v)
if err == nil {
kv.store[buff[1]] = fmt.Sprintf("%d", val+1)
} else {
res = []byte("-ERR value is not an integer or out of range\r\n")
break
}
}
res = []byte(fmt.Sprintf(":%s\r\n", kv.store[buff[1]]))
Use Cases
Caching
# Cache a user session
SET session:user123 "{\"userId\": 123, \"name\": \"John\"}" PX 3600000
GET session:user123
Counters
# Page view counter
INCR page:views:homepage
INCR page:views:homepage
GET page:views:homepage
# Response: 2
Rate Limiting
# Track API calls with 60-second window
SET rate:user123 "0" PX 60000
INCR rate:user123
INCR rate:user123
GET rate:user123
# Response: 2
