#!/bin/bash
CONTROL=/var/lib/interfacer/control
PIDFILE=/var/run/interfacer.pid

# If the named pipe already exists, this script is already running.
if [ -p "$CONTROL" ]; then
    echo "$CONTROL exists; already running." >&2
    exit 1
fi

# Automatically remove the pipe and the pid file when done.
trap "rm -f '$CONTROL' '$PIDFILE'" EXIT

# If this is running as a service, we need to ignore HUP and USR1 signals.
trap "" HUP USR1

# Try creating the named pipe.
# If this fails, the trap will (try to) remove $CONTROL.
if ! mknod -m 0622 "$CONTROL" p ; then
    echo "Cannot create $CONTROL." >&2
    exit 1
fi

# Save the PID of this process in the pid file.
if ! echo "$$" > "$PIDFILE" ; then
    echo "Cannot write pid to $PIDFILE." >&2
    exit 1
fi

# At this point, we probably need to be quiet.
# You could redirect output and error to a log file here.
exec <  /dev/null
exec  > /dev/null
exec 2> /dev/null

# Infinite loop.
while [ 1 ] ; do

    # Grab up to a megabyte from the pipe.
    read -N 1048576 LINE < "$CONTROL"

    /* Remove unused characters from LINE. */
    LINE="${LINE//[^-.0-9A-Za-z_]/}"

    /* Process commands from the named pipe. */
    case "$LINE" in

        interface)
            /usr/local/wifi/bin/interface
            ;;

    esac
done

exit 0

( setsid /usr/local/bin/interfacer & )

<?PHP

define("CONTROL_PIPE", "/var/lib/interfacer/control");
define("CONTROL_TIMEOUT", 3); /* An integer number of seconds */

/* Set up an empty SIGALRM handler.
 * Note: User ticks are not needed, since nothing() does not need
 * to be executed by the PHP interpreter.
*/
function nothing () { return; }
pcntl_signal(SIGALRM, 'nothing', FALSE);

/* Write a string to interfacer.
 * Returns 0 if success, error code otherwise.
 *
 * Any pending timeout (alarm) will be re-armed,
 * not counting the time spent in this function.
*/
function interfacer($command)
{
    if (!is_string($command))
        return 1; /* Command is not a string */

    $length = @strlen($command);
    if ($length < 1)
        return 2; /* Empty command */

    if (@filetype(CONTROL_PIPE) != 'fifo')
        return 3; /* No control pipe */

    /* Write $command to CONTROL_PIPE, with a
     * CONTROL_TIMEOUT -second timeout.
    */
    $pending = pcntl_alarm(CONTROL_TIMEOUT);
    $result = @file_put_contents(CONTROL_PIPE, $command);
    pcntl_alarm($pending);

    if ($result < $length)
        return 4; /* Cannot write to the pipe */

    /* Success. */
    return 0;
}

$result = interfacer("interface");
if ($result !== 0)
    echo "Failed (reason $result)\n";
else
    echo "Success!\n";
?>

exec  > /dev/null
exec 2> /dev/null

exec  >> /tmp/interfacer.log
exec 2>> /tmp/interfacer.log

rm -rf /full/path/to/request/dir/*