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+Set `key` to hold the string `value`. If `key` already holds a value, it is
+overwritten, regardless of its type. Any previous time to live associated with
+the key is discarded on successful `SET` operation.
+
+## Options
+
+The `SET` command supports a set of options that modify its behavior:
+
+- `EX` _seconds_ -- Set the specified expire time, in seconds.
+- `PX` _milliseconds_ -- Set the specified expire time, in milliseconds.
+- `NX` -- Only set the key if it does not already exist.
+- `XX` -- Only set the key if it already exist.
+- `KEEPTTL` -- Retain the time to live associated with the key.
+
+Note: Since the `SET` command options can replace `SETNX`, `SETEX`, `PSETEX`, it
+is possible that in future versions of Redis these three commands will be
+deprecated and finally removed.
+
+@return
+
+@simple-string-reply: `OK` if `SET` was executed correctly. @nil-reply: a Null
+Bulk Reply is returned if the `SET` operation was not performed because the user
+specified the `NX` or `XX` option but the condition was not met.
+
+@history
+
+- `>= 2.6.12`: Added the `EX`, `PX`, `NX` and `XX` options.
+- `>= 6.0`: Added the `KEEPTTL` option.
+
+@examples
+
+```cli
+SET mykey "Hello"
+GET mykey
+
+SET anotherkey "will expire in a minute" EX 60
+```
+
+## Patterns
+
+**Note:** The following pattern is discouraged in favor of
+[the Redlock algorithm](http://redis.io/topics/distlock) which is only a bit
+more complex to implement, but offers better guarantees and is fault tolerant.
+
+The command `SET resource-name anystring NX EX max-lock-time` is a simple way to
+implement a locking system with Redis.
+
+A client can acquire the lock if the above command returns `OK` (or retry after
+some time if the command returns Nil), and remove the lock just using `DEL`.
+
+The lock will be auto-released after the expire time is reached.
+
+It is possible to make this system more robust modifying the unlock schema as
+follows:
+
+- Instead of setting a fixed string, set a non-guessable large random string,
+  called token.
+- Instead of releasing the lock with `DEL`, send a script that only removes the
+  key if the value matches.
+
+This avoids that a client will try to release the lock after the expire time
+deleting the key created by another client that acquired the lock later.
+
+An example of unlock script would be similar to the following:
+
+    if redis.call("get",KEYS[1]) == ARGV[1]
+    then
+        return redis.call("del",KEYS[1])
+    else
+        return 0
+    end
+
+The script should be called with `EVAL ...script... 1 resource-name token-value`