README: Some usage examples

Author: shazow

README.md

@@ -9,9 +9,12 @@ Usage: ./execd [options] <auth-handler> <exec-handler>
   -d=false: debug mode displays handler output
   -e=false: pass environment to handlers
   -k="": pem file of private keys (read from SSH_PRIVATE_KEYS by default)
+  -h="": host ip to listen on
   -p="22": port to listen on
   -s=false: run exec handler via SHELL
 ```
+
+
 #### auth-handler $user $key
 
  * `$user` argument is the name of the user being used to attempt the connection
@@ -21,12 +24,47 @@ auth-handler is the path to an executable that's used for authenticating incomin
 
 Although auth-handler is required, you can still achieve no-auth open access by providing `/usr/bin/true` as auth-handler.
 
+
 #### exec-handler $command...
 
  * `$command...` arguments is the command line that was specified to run by the SSH client
 
 exec-handler is the path to an executable that's used to execute the command provided by the client. The meaning of that is quite flexible. All of the stdout and stderr is returned to the client, including the exit status. If the client provides stdin, that's passed to the exec-handler. Any environment variables provided by the auth-handler output will be available to exec-handler, as well as `$USER` and `$SSH_ORIGINAL_COMMAND` environment variables.
 
+
+## Examples
+
+**These examples bypass all authentication and allow remote execution, *do not* run this in production.**
+
+Echo server (with accept-all auth):
+
+```
+server$ execd $(which true) $(which echo)
+client$ ssh $SERVER "hello world"
+hello world
+```
+
+Echo host's environment to clients
+
+```
+server$ execd -e $(which true) $(env)
+client$ ssh $SERVER
+USER=root
+HOME=/root
+LANG=en_US.UTF-8
+...
+```
+
+Bash server (with accept-all auth):
+
+```
+server$ execd $(which true) $(which bash)
+client$ ssh $SERVER
+bash-4.3$ echo "this is a bash instance running on the server"
+this is a bash instance running on the server
+```
+
+
 ## Credit / History
 
 It started with [gitreceive](https://github.com/progrium/gitreceive), which was then used in [Dokku](https://github.com/progrium/dokku). Then I made a more generalized version of gitreceive, more similar to execd, called [sshcommand](https://github.com/progrium/sshcommand), which eventually replaced gitreceive in Dokku. When I started work on Flynn, the first projects included [gitreceived](https://github.com/flynn/gitreceived) (a standalone daemon version of gitreceive). This was refined by the Flynn community, namely Jonathan Rudenberg. 
@@ -39,4 +77,4 @@ This project was made possible thanks to [DigitalOcean](http://digitalocean.com)
 
 ## License
 
-BSD
+BSD