BITPOS

BITPOS returns the position of the first bit equal to bit (0 or 1) in the string at key. The position is always counted from the start of the string, in bits, even when you search a range. start and end limit the search; negative values count back from the end, and by default they are byte offsets (add BIT for bit offsets).

When looking for a 0 bit without an end, the string is treated as if it continued with zero bits, so a string with every bit set returns the first position after its end. With an explicit end, a range without the bit returns -1. A missing key returns 0 when looking for 0 and -1 when looking for 1.

Options

Option	Effect
start	Begin the search at this offset.
end	Stop the search at this offset, included.
BYTE	start and end are byte offsets (the default).
BIT	start and end are bit offsets.

Return value

Case	RESP2	RESP3
Found	Integer: the bit position	Integer
Not found	Integer -1 (or the position after the end, see above)	Integer

Errors:

• ERR bit is not an integer or out of range when bit is not 0 or 1.
• ERR value is not an integer or out of range when start or end is not an integer.
• ERR syntax error for a unit other than BYTE or BIT.
• WRONGTYPE when the key holds a value that is not a string.

Examples

127.0.0.1:6379> SET mask "hi"
OK
127.0.0.1:6379> BITPOS mask 1
(integer) 1
127.0.0.1:6379> BITPOS mask 1 1
(integer) 9
127.0.0.1:6379> BITPOS mask 1 7 15 BIT
(integer) 9
127.0.0.1:6379> SET full "\xff"
OK
127.0.0.1:6379> BITPOS full 0
(integer) 8
127.0.0.1:6379> BITPOS full 0 0 0
(integer) -1

Compatibility

Same results as Redis 7 and Valkey 8. With more than six arguments HotKV replies with ERR wrong number of arguments for 'bitpos' command, where Redis replies ERR syntax error.

See also

BITCOUNT, GETBIT, SETBIT