Update README.md with listener.conf's format

README.md

@@ -8,6 +8,49 @@ Such commands are described as rules that also include the directory
 to watch, which kind of file objects to watch, and a regular expression
 that whitelists the file names that are subject to processing.
 
+# Listener.conf format
+
+Listener's config file accepts multiple rules. Each rule must be enclosed
+with brackets ("{" and "}") and needs to contain the following sequence of
+keys:
+
+- **TARGET**: pathname to listen
+
+- **WATCHES**: file system / inotify events to watch. The following flags are
+  recognized and may be combined with the OR ("|") operator:
+  - *ACCESS*: file  has been accessed on the watched directory
+  - *MODIFY*: file has been modified on the watched directory
+  - *ATTRIB*: attributes (e.g., permissions, timestamps, ownership) have changed
+  - *CLOSE_WRITE*: file has been opened for writing and has now been closed
+  - *CLOSE_NOWRITE*: file or directory has been opened for reading only and has now been closed
+  - *OPEN*: file or directory was opened
+  - *MOVED_FROM*: a file or directory has been moved from the watched directory to somewhere else
+  - *MOVED_TO*: a file or directory has been moved to the watched directory
+  - *CREATE*: a file or directory was created on the watched directory
+  - *DELETE*: a file or directory has been deleted
+  - *DELETE_SELF*: watched file/directory has been deleted itself
+  - *MOVE_SELF*: watched file/directory has been moved itself
+
+- **SPAWN**: shell command to invoke when the event is triggered. In special,
+  the string $ENTRY can be used to represent the file or directory name that
+  triggered the event.
+
+- **LOOKAT**: file types to consider under the watched directory. The following
+  types are recognized and may be combined with the OR ("|") operator:
+  - *DIRS*: directories
+  - *FILES*: regular files
+  - *SYMLINKS*: symbolic links
+
+- **ACCEPT_REGEX**: a regular expression that indicates the file name patterns to
+  process. This is useful if you are watching a directory that holds both MP3 and
+  AVI files, for instance, but want to have a listener rule that only processes one
+  of the two. You can use the wildcard character to catch all files.
+
+- **RECURSIVE_DEPTH**: how many levels below TARGET to watch. A depth of 0 will
+  look for events on file system objects that are immediate children of TARGET.
+  A depth of 1 will look for events on objects that are both immediate children
+  of TARGET and also children of its 1st level subdirectories, and so on.
+
 # Sample rule file
 
 The following example holds a rule that watches for DELETE events on