etcdctlv3: interactive_v3 del command update

Documentation/dev-guide/interacting_v3.md

@@ -48,7 +48,7 @@ Applications can read values of keys from an etcd cluster. Queries may read a si
 
 Suppose the etcd cluster has stored the following keys:
 
-```
+```bash
 foo = bar
 foo1 = bar1
 foo3 = bar3
@@ -167,6 +167,20 @@ z
 
 Applications can delete a key or a range of keys from an etcd cluster.
 
+Suppose an etcd cluster already has the following keys:
+
+```bash
+foo = bar
+foo1 = bar1
+foo3 = bar3
+zoo = val
+zoo1 = val1
+zoo2 = val2
+a = 123
+b = 456
+z = 789
+```
+
 Here is the command to delete key `foo`:
 
 ```bash
@@ -181,6 +195,29 @@ $ etcdctl del foo foo9
 2 # two keys are deleted
 ```
 
+Here is the command to delete key `zoo` with the deleted key value pair returned:
+
+```bash
+$ etcdctl del --prev-kv zoo 
+1   # one key is deleted
+zoo # deleted key
+val # the value of the deleted key
+```
+
+Here is the command to delete keys having prefix as `zoo`:
+
+```bash
+$ etcdctl del --prefix zoo 
+2 # two keys are deleted
+```
+
+Here is the command to delete keys which are greater than or equal to the byte value of key `b` :
+
+```bash
+$ etcdctl del --from-key b
+2 # two keys are deleted
+```
+
 ## Watch key changes
 
 Applications can watch on a key or a range of keys to monitor for any updates.