【redis】list类型命令简述

redis的list类型，可以存储双向链表作为value，key保留有head和tail指针可以指向双向链表的头和尾，因此可以直接从头或尾对list进行操作。
全部命令如下：

127.0.0.1:6379> help @list

  BLMOVE source destination LEFT|RIGHT LEFT|RIGHT timeout
  summary: Pop an element from a list, push it to another list and return it; or block until one is available
  since: 6.2.0

  BLMPOP timeout numkeys key [key ...] LEFT|RIGHT [COUNT count]
  summary: Pop elements from a list, or block until one is available
  since: 7.0.0

  BLPOP key [key ...] timeout
  summary: Remove and get the first element in a list, or block until one is available
  since: 2.0.0

  BRPOP key [key ...] timeout
  summary: Remove and get the last element in a list, or block until one is available
  since: 2.0.0

  BRPOPLPUSH source destination timeout
  summary: Pop an element from a list, push it to another list and return it; or block until one is available
  since: 2.2.0

  LINDEX key index
  summary: Get an element from a list by its index
  since: 1.0.0

  LINSERT key BEFORE|AFTER pivot element
  summary: Insert an element before or after another element in a list
  since: 2.2.0

  LLEN key
  summary: Get the length of a list
  since: 1.0.0

  LMOVE source destination LEFT|RIGHT LEFT|RIGHT
  summary: Pop an element from a list, push it to another list and return it
  since: 6.2.0

  LMPOP numkeys key [key ...] LEFT|RIGHT [COUNT count]
  summary: Pop elements from a list
  since: 7.0.0

  LPOP key [count]
  summary: Remove and get the first elements in a list
  since: 1.0.0

  LPOS key element [RANK rank] [COUNT num-matches] [MAXLEN len]
  summary: Return the index of matching elements on a list
  since: 6.0.6

  LPUSH key element [element ...]
  summary: Prepend one or multiple elements to a list
  since: 1.0.0

  LPUSHX key element [element ...]
  summary: Prepend an element to a list, only if the list exists
  since: 2.2.0

  LRANGE key start stop
  summary: Get a range of elements from a list
  since: 1.0.0

  LREM key count element
  summary: Remove elements from a list
  since: 1.0.0

  LSET key index element
  summary: Set the value of an element in a list by its index
  since: 1.0.0

  LTRIM key start stop
  summary: Trim a list to the specified range
  since: 1.0.0

  RPOP key [count]
  summary: Remove and get the last elements in a list
  since: 1.0.0

  RPOPLPUSH source destination
  summary: Remove the last element in a list, prepend it to another list and return it
  since: 1.2.0

  RPUSH key element [element ...]
  summary: Append one or multiple elements to a list
  since: 1.0.0

  RPUSHX key element [element ...]
  summary: Append an element to a list, only if the list exists
  since: 2.2.0

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下面示例如下：

lpush：lpush key e1 e2 e3…将数据从头那里推入list
lpop：lpop key，将数据从head弹出
这样2个同向的命令组合起来，可以实现一个队列。
反向的命令组合起来，可以实现一个栈。

127.0.0.1:6379> lpush k1 a b c d e
(integer) 5
127.0.0.1:6379> lpop k1
"e"
127.0.0.1:6379> lpop k1
"d"

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lrange ：lrange key start end，展示key对应的从下标start到end的所有数据

127.0.0.1:6379> lrange k1 0 -1
1) "c"
2) "b"
3) "a"

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lindex：lindex key index ，返回key对应的List指定index位置的值

127.0.0.1:6379> lrange k1 0 -1
1) "f"
2) "e"
3) "d"
4) "c"
5) "b"
6) "a"
127.0.0.1:6379> lindex k1 1
"e"

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lset：lset key index value，在key对应的list中的指定下标处替换为value

127.0.0.1:6379> lset k1 3 x
OK
127.0.0.1:6379> lrange k1 0 -1
1) "f"
2) "e"
3) "d"
4) "x"
5) "b"
6) "a"

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lrem：lrem key num target，删除key对应的list中的target元素，如果num大于0，从head开始删num个。如果num小于0，从tail开始删abs(num)个

127.0.0.1:6379> lrange k3 0 -1
 1) "d"
 2) "6"
 3) "a"
 4) "5"
 5) "c"
 6) "4"
 7) "a"
 8) "3"
 9) "b"
10) "2"
11) "a"
12) "1"
127.0.0.1:6379> lrem k3 2 a
(integer) 2
127.0.0.1:6379> lrange k3 0 -1
 1) "d"
 2) "6"
 3) "5"
 4) "c"
 5) "4"
 6) "3"
 7) "b"
 8) "2"
 9) "a"
10) "1"



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linsert：linsert key before/after element value，在key对应的list中，在元素element（不是下标）之前或者之后，添加value

127.0.0.1:6379> lrange k3 0 -1
 1) "d"
 2) "6"
 3) "5"
 4) "c"
 5) "4"
 6) "3"
 7) "b"
 8) "2"
 9) "a"
10) "1"
127.0.0.1:6379> linsert k3 after 6 a
(integer) 11
127.0.0.1:6379> lrange k3 0 -1
 1) "d"
 2) "6"
 3) "a"
 4) "5"
 5) "c"
 6) "4"
 7) "3"
 8) "b"
 9) "2"
10) "a"
11) "1"

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llen：llen key，返回长度
redis的List类型有很多关于下标的操作，也可以将其抽象为一个数组来使用。

127.0.0.1:6379> llen k3
(integer) 10

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blpop：blpop key time，弹出指定key对应的list中的一个元素，如果list没有元素或者不存在key对应的这个list，则阻塞等待time指定的时间，0表示一直等待，单位是s。

127.0.0.1:6379> blpop k1 0
1

阻塞期间如果list有了元素，则会中断阻塞并弹出

127.0.0.1:6379> blpop k1 0
1) "k1"
2) "a"
(35.77s)

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ltrim：ltrim key start end，删除key对应的list start和end之外的两端的元素

127.0.0.1:6379> lrange k4 0 -1
1) "f"
2) "e"
3) "d"
4) "c"
5) "b"
6) "a"
127.0.0.1:6379> ltrim k4 1 -2
OK
127.0.0.1:6379> lrange k4 0 -1
1) "e"
2) "d"
3) "c"
4) "b"

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