setnx

setnx(set if not exist) 设置一个键值,并判断是否有相同键名

127.0.0.1:6379> set test 123
OK
127.0.0.1:6379> get test
"123"
127.0.0.1:6379> setnx test 123
(integer) 0
127.0.0.1:6379> setnx test1 123
(integer) 1
127.0.0.1:6379> get test1
"123"