Add README

README.md

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+redis-del-keys
+==============
+
+Delete keys in Redis by a pattern. Deletion is performed by doing [`SCAN`][scan]
+and then invoking DEL in a [pipeline]. This allows you to delete the keys in a
+non-blocking manner.
+
+## Usage
+
+Simple invocation requires pattern argument:
+
+    $ redis-del-keys 
+    pattern argument is required
+
+    redis-iter-del iterates over redis keys with SCAN matched by pattern and then
+    DEL the keys in pipelined commands
+
+    Usage of redis-del-keys:
+      -a, --addrs strings    Redis addrs, comma separated for cluster (default [:6379])
+      -b, --batch int        Batch size for pipelined commands (default 10)
+      -c, --count int        Count for SCAN command (default 10)
+      -d, --dryrun           Dry run
+      -p, --pattern string   Pattern to delete
+
+This prevents you from accidentally deleting all of the keys.
+
+Real example:
+
+    $ redis-del-keys -p 'a*'
+    iterated over 10 keys
+
+It prints how many keys it has iterated. Running this command again will iterate
+over 0 keys because they were deleted:
+
+    $ redis-del-keys -p 'a*'
+    iterated over 0 keys
+
+The command supports **dry run mode** via `-d` or `--dryrun` option. It is safe
+and allows you to estimate how many keys will be deleted:
+
+    $ redis-del-keys -d -p '*'
+    iterated over 240 keys
+
+
+[scan]: https://redis.io/commands/scan
+[pipeline]: https://redis.io/topics/pipelining