Skip to main content

GETBIT

Returns the bit value at the specified offset in the string stored at a key.

Syntax​

GETBIT key offset

Parameters​

  • key: The name of the key containing the string.
  • offset: The bit offset to retrieve, which is a zero-based index.

Details​

  • Available since: 2.2.0
  • Time complexity: O(1)
  • ACL categories: @read, @string, @fast

The GETBIT command retrieves the bit value at a specified offset in a string stored at key. The bit offset is zero-based, meaning an offset of 0 refers to the first bit of the string. The command returns 0 or 1, indicating the value of the bit at the specified position.

If the key does not exist, it is treated as an empty string, and GETBIT will return 0 for any offset.

Examples​

Basic Usage​

Assume we have the following key with a string value:

SETBIT mykey 0 1
SETBIT mykey 1 0
SETBIT mykey 2 1

To get the bit value at offset 1:

GETBIT mykey 1

This will return:

0

Retrieving a Bit from an Empty Key​

If the key mykey does not exist, the following command will return 0 for any offset:

GETBIT mykey 5

This will return:

0

Retrieving a Bit from a Non-Existing Offset​

If the offset is beyond the current length of the string (e.g., offset 10 for a string of length 3), the command will still return 0:

GETBIT mykey 10

This will return:

0

Edge Cases​

  • If the key does not exist, it is treated as a string of zero length, so all bit offsets return 0.
  • If the offset is negative or out of range for the string, GETBIT will return 0.

RESP2/RESP3 Reply​

  • Integer reply: the bit value at the specified offset, which is 0 or 1.