hsetnx

Sets field in the hash stored at key to value, only if field does not yet exist. If key does not exist, a new key holding a hash is created. If field already exists, this operation has no effect.

Examples

127.0.0.1:6379> HSETNX myhash field "Hello"
(integer) 1
127.0.0.1:6379> HSETNX myhash field "World"
(integer) 0
127.0.0.1:6379> HGET myhash field
"Hello"