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BLMOVE

Syntax​

BLMOVE source destination <LEFT | RIGHT> <LEFT | RIGHT> timeout

Time complexity: O(1)

ACL categories: @write, @list, @slow, @blocking

BLMOVE is the blocking variant of LMOVE. If the source list contains elements, the command behaves like LMOVE.

If the source list is empty or does not exist, the connected client will be blocked until another client pushes an element to source, or until the specified timeout is reached.

  • A timeout of 0 blocks indefinitely until an element is available.
  • If the timeout expires without an element becoming available, the command returns nil and no element is moved.

See also: LMOVE for the command options.

Return​

  • Bulk string reply: the element being popped from source and pushed to destination, when successful.
  • Nil reply when the command times out.

Examples​

Moving an Element​

dragonfly> RPUSH src a b c
(integer) 3
dragonfly> RPUSH dst x y
(integer) 2
dragonfly> BLMOVE src dst RIGHT LEFT 0
"c"
dragonfly> LRANGE src 0 -1
1) "a"
2) "b"
dragonfly> LRANGE dst 0 -1
1) "c"
2) "x"
3) "y"

Blocking with Non-Zero Timeout​

dragonfly> DEL src dst
(integer) 0
dragonfly> BLMOVE empty dst LEFT RIGHT 1.5
(nil)