# LMOVEM ```json metadata { "title": "LMOVEM", "description": "Moves up to (or exactly) a number of elements from one list to another and returns them. Deletes the source list if it becomes empty.", "categories": ["docs","develop","stack","oss","rs","rc","oss","kubernetes","clients"], "arguments": [{"display_text":"source","key_spec_index":0,"name":"source","type":"key"},{"display_text":"destination","key_spec_index":1,"name":"destination","type":"key"},{"arguments":[{"display_text":"left","name":"left","token":"LEFT","type":"pure-token"},{"display_text":"right","name":"right","token":"RIGHT","type":"pure-token"}],"name":"wherefrom","type":"oneof"},{"arguments":[{"display_text":"left","name":"left","token":"LEFT","type":"pure-token"},{"display_text":"right","name":"right","token":"RIGHT","type":"pure-token"}],"name":"whereto","type":"oneof"},{"arguments":[{"arguments":[{"display_text":"count","name":"count","token":"COUNT","type":"integer"},{"display_text":"exactly","name":"exactly","token":"EXACTLY","type":"integer"}],"name":"selector","type":"oneof"},{"arguments":[{"display_text":"obo","name":"obo","token":"OBO","type":"pure-token"},{"display_text":"bulk","name":"bulk","token":"BULK","type":"pure-token"}],"name":"ordering","type":"oneof"}],"name":"how-many","optional":true,"type":"block"}], "syntax_fmt": "LMOVEM source destination \u003cLEFT | RIGHT\u003e \u003cLEFT | RIGHT\u003e\n [\u003cCOUNT count | EXACTLY exactly\u003e \u003cOBO | BULK\u003e]", "complexity": "O(N) where N is the number of elements moved.", "group": "list", "command_flags": ["write","denyoom"], "acl_categories": ["@write","@list","@slow"], "since": "8.10.0", "arity": -5, "key_specs": [{"RW":true,"access":true,"begin_search":{"spec":{"index":1},"type":"index"},"delete":true,"find_keys":{"spec":{"keystep":1,"lastkey":0,"limit":0},"type":"range"}},{"RW":true,"begin_search":{"spec":{"index":2},"type":"index"},"find_keys":{"spec":{"keystep":1,"lastkey":0,"limit":0},"type":"range"},"insert":true}], "tableOfContents": {"sections":[{"id":"required-arguments","title":"Required arguments"},{"id":"optional-arguments","title":"Optional arguments"},{"id":"examples","title":"Examples"},{"children":[{"id":"moving-multiple-elements","title":"Moving multiple elements"},{"id":"element-ordering","title":"Element ordering"}],"id":"details","title":"Details"},{"id":"redis-software-and-redis-cloud-compatibility","title":"Redis Software and Redis Cloud compatibility"},{"id":"return-information","title":"Return information"},{"id":"see-also","title":"See also"},{"id":"related-topics","title":"Related topics"}]} , "codeExamples": [] } ``` This command's behavior varies in clustered Redis environments. See the [multi-key operations](https://redis.io/docs/latest/develop/using-commands/multi-key-operations) page for more information. Atomically moves one or more elements from the list stored at `source` to the list stored at `destination` and returns the moved elements. `LMOVEM` is the multiple-element version of [`LMOVE`](https://redis.io/docs/latest/commands/lmove): without the optional `how-many` block, it behaves exactly like [`LMOVE`](https://redis.io/docs/latest/commands/lmove) but returns the moved element as a one-element array. ## Required arguments
source The key of the source list.
destination The key of the destination list.
LEFT | RIGHT The end of `source` to pop elements from: `LEFT` (head) or `RIGHT` (tail).
LEFT | RIGHT The end of `destination` to push elements to: `LEFT` (head) or `RIGHT` (tail).
## Optional arguments The `how-many` block controls how many elements are moved and in what order. When you include it, you must provide both a selector (`COUNT` or `EXACTLY`) and an ordering (`OBO` or `BULK`).
COUNT count | EXACTLY exactly The number of elements to move: - `COUNT count` moves up to `count` elements. If `source` holds fewer than `count` elements, all of them are moved. This matches the `count` semantics of [`LPOP`](https://redis.io/docs/latest/commands/lpop) and [`LMPOP`](https://redis.io/docs/latest/commands/lmpop). - `EXACTLY exactly` moves exactly `exactly` elements. If `source` holds fewer than `exactly` elements, nothing is moved and the command returns nil.
OBO | BULK The order in which elements are pushed onto `destination`: - `OBO` (one by one) moves elements individually: each element is popped from `source` and pushed to `destination` before the next one is moved. - `BULK` moves all of the elements at once, preserving their relative order. The two orderings differ only in the resulting arrangement of elements. See [Element ordering](#element-ordering) for details.
## Examples ``` > rpush mylist 1 2 3 4 (integer) 4 > LMOVEM mylist myotherlist LEFT LEFT COUNT 2 OBO 1) "2" 2) "1" > LRANGE mylist 0 -1 1) "3" 2) "4" > LRANGE myotherlist 0 -1 1) "2" 2) "1" > LMOVEM mylist myotherlist LEFT LEFT EXACTLY 5 BULK (nil) > RPUSH somelist a b c (integer) 3 > LMOVEM somelist somelist LEFT LEFT EXACTLY 2 OBO 1) "b" 2) "a" > LRANGE somelist 0 -1 1) "b" 2) "a" 3) "c" ``` ## Details ### Moving multiple elements `LMOVEM` moves elements from one end of `source` (selected by the first `LEFT | RIGHT` argument) to one end of `destination` (selected by the second `LEFT | RIGHT` argument), and returns the moved elements as an array. If `source` does not exist, no operation is performed and the command returns an empty array (or nil when `EXACTLY` is used). The `COUNT` and `EXACTLY` selectors decide how many elements are moved: - With `COUNT count`, the command moves up to `count` elements. If `source` holds fewer than `count` elements, all available elements are moved. - With `EXACTLY exactly`, the command moves the requested number of elements only if `source` holds at least that many. Otherwise it moves nothing and returns nil. This is useful when elements form fixed-size groups (for example, pairs or triplets) that must be moved together or not at all. ### Element ordering The `OBO` and `BULK` orderings determine how the moved elements are arranged on `destination`: - `OBO` (one by one) pops and pushes each element in turn, so an element popped earlier ends up "beneath" one popped later at the destination end. - `BULK` moves the whole batch at once, preserving the elements' relative order. When `source` and `destination` are the same key, this difference becomes a useful side effect. `BULK` leaves the list unchanged (the elements are removed and re-added in the same order), so it is effectively a no-op. `OBO`, however, reverses the moved elements in place. For example, with `mylist` holding `a, b, c`, running `LMOVEM mylist mylist LEFT LEFT EXACTLY 2 OBO` pops `a` then `b` and pushes each back to the head, leaving `mylist` as `b, a, c`. ## Redis Software and Redis Cloud compatibility | Redis
Software | Redis
Cloud | Notes | |:----------------------|:-----------------|:------| | ❌ Standard
❌ Active-Active | ❌ Standard
❌ Active-Active | | ## Return information **RESP2:** One of the following: * [Array reply](../../develop/reference/protocol-spec#arrays): the moved elements, in destination order. * [Nil reply](../../develop/reference/protocol-spec#bulk-strings): if `EXACTLY` was used and `source` did not hold enough elements. **RESP3:** One of the following: * [Array reply](../../develop/reference/protocol-spec#arrays): the moved elements, in destination order. * [Null reply](../../develop/reference/protocol-spec#nulls): if `EXACTLY` was used and `source` did not hold enough elements. ## See also [`LMOVE`](https://redis.io/docs/latest/commands/lmove/) | [`BLMOVEM`](https://redis.io/docs/latest/commands/blmovem/) | [`LMPOP`](https://redis.io/docs/latest/commands/lmpop/) | [`RPOPLPUSH`](https://redis.io/docs/latest/commands/rpoplpush/) ## Related topics - [Redis lists](https://redis.io/docs/latest/develop/data-types/lists)