Add informations about commands to readme

README.md

@@ -50,3 +50,39 @@ one you built.
 `receive`. All commands do not have to be specified fully. If the
 command is clearly distinguishable from all the others, it does not
 have to be completed further.
+
+### Create a message queue
+Use the `create` command to create a new POSIX message queue. Following
+optional arguments are supported:
+- `-c`, `--capacity`: Maximum number of messages in the queue
+- `-p`, `--permissions`: Permissions (octal) to create the queue with
+- `-s`, `--msgsize`: Message size in bytes
+
+### Print information about a message queue
+Use the `info` command to print further information about a message
+queue.
+
+### Delete a message queue
+Use the `unlink` command to delete a message queue.
+
+### Send a message to a queue
+Use the `send` command to send a message to a message queue. Following
+optional arguments are supported:
+- `-n`, `--non-blocking`: Do not block
+- `-d`, `--deadline <deadline>`: Deadline until messages are sent
+  (format: `%Y-%m-%d %H:%M:%S`)
+- `-p`, `--priority <priority>`: Use priority PRIO, PRIO >= 0
+  [default: 0]
+- `-o`, `--timeout <timeout>`: Timeout in `<timeout>[s]` (default) or
+  `<timeout>ms`
+
+### Receive a message from a queue
+Use the `recv` command to receive one or more messages from a message
+queue. Following optional arguments are supported:
+- `-f`, `--follow`: Print messages as they are received
+- `-n`, `--non-blocking`: Do not block
+- `-t`, `--timestamp`: Print a timestamp before each message
+- `-d`, `--deadline <deadline>`: Deadline until messages are received
+  (format: `%Y-%m-%d %H:%M:%S`)
+- `-o,` `--timeout <timeout>`: Timeout in `<timeout>[s]` (default) or
+  `<timeout>ms`