+If the *-u*, *-r* or *-p* option is presented with an empty argument,
+it will be treated as if the option had not been given.
+
+SIGNALS
+-------
+
+SIGTERM, SIGINT::
+
+ Upon first reception, `htparser` closes all listening ports
+ and the socket to the root handler, but continues to serve all
+ currently ongoing requests until none remain, not keeping the
+ connections open for keep-alive. Upon second reception,
+ `htparser` shuts down completely.
+
+PID-FILE PROTOCOL
+-----------------
+
+If the *-p* option is used to create a PID file, `htparser` will
+follow a simple protocol to allow state monitoring for clean shutdown
+purposes. When `htparser` is signalled to terminate, as described
+under SIGNALS, then it appends a single newline at the end of the PID
+file. Once all outstanding connections have been terminated, then
+`htparser` will truncate the PID file to zero size just prior to
+exiting. Thus, init scripts or other state-monitoring tools can know
+that `htparser` is serving remaining connections as long as the PID
+file contains two lines (the last of which is empty).
+
+Further, when `htparser` starts, it does not overwrite the contents of
+an existing PID file, but rather creates a new file, replacing the old
+file. Thus, if a new instance of `htparser` is started while a
+previous instance is still running (or serving remaining connections),
+the PID file for the new instance will not be truncated when the
+previous instance terminates.
+
+The reason for the somewhat unorthodox protocol is that it works by
+simply keeping the PID file open in the running process, allowing the
+protocol to work without pathnames, and therefore even if `htparser`
+is instructed to change root directory with the *-r* option.
+
+EXAMPLES
+--------
+
+`htparser plain -- dirplex /srv/www`::
+
+ This simple invocation will listen for HTTP requests on port
+ 80 and use *dirplex*(1) to serve files from the /srv/www
+ directory.
+
+`htparser plain:port=8080 -- dirplex /srv/www`::
+
+ The same as the previous example, but uses port 8080 instead,
+ so that it can be started without root privileges.
+
+`htparser plain ssl:cert=/etc/ssl/private/web.pem -- dirplex /srv/www`::
+
+ The same as above, but will listen on port 443 for SSL
+ connections as well. The file `/etc/ssl/private/web.pem` needs
+ to contain both the server certificate and its private key.
+
+`htparser plain -- sudo -u www-user dirplex /srv/www`::
+
+ The same as above, but uses *sudo*(8) to ensure that *dirplex*
+ runs as a non-privileged user.
+
+`htparser -f -u nobody -r /var/empty plain -- patplex /etc/ashd/rootpat`::
+
+ Will listen to port 80 for plain HTTP requests and use the
+ *patplex*(1) program to serve requests based on patterns
+ specified in the `/etc/ashd/rootpat` file. *htparser* will
+ daemonize, change user-ID to `nobody` and change its root
+ directory to `/var/empty` once *patplex* has been
+ started. Note that *patplex* still runs as root in the normal
+ file system, so that it can start other handler programs as
+ needed.
+
+`htparser -f plain -- errlogger -n ashd dirplex /srv/www`::
+
+ The same as the first example, but will daemonize and use the
+ *errlogger*(1) program to ensure that any errors or other
+ messages written by any handler program to its stderr are
+ recorded in the *syslog*(3).
+
+X-ASH HEADERS
+-------------
+
+*htparser* strips away all headers from incoming requests that begin
+ with the `X-Ash-` prefix, and adds the following headers to requests:
+
+*X-Ash-Address*::
+
+ The IP address that the client connected from. May be an IPv6
+ address.
+
+*X-Ash-Port*::
+
+ The client-side port number of the TCP connection.
+
+*X-Ash-Server-Address*::
+
+ The IP address of the server where the connection was
+ accepted. May be an IPv6 address.
+
+*X-Ash-Server-Port*::
+
+ The server-side port number of the TCP connection.
+
+*X-Ash-Protocol*::
+
+ Either *http* or *https*, depending on whether the request was
+ received by the *plain* or the *ssl* handler.
+