GUAC-1452: Provide for storage of pipe stream within terminal struct.

src/terminal/terminal.c

@@ -326,6 +326,9 @@ guac_terminal* guac_terminal_create(guac_client* client,
         return NULL;
     }
 
+    /* Init pipe stream (output to display by default) */
+    term->pipe_stream = NULL;
+
     /* Init terminal lock */
     pthread_mutex_init(&(term->lock), NULL);
 

src/terminal/terminal.h

@@ -149,6 +149,13 @@ struct guac_terminal {
      */
     int stdin_pipe_fd[2];
 
+    /**
+     * The currently-open pipe stream to which all terminal output should be
+     * written, if any. If no pipe stream is open, terminal output will be
+     * written to the terminal display, and this value will be NULL.
+     */
+    guac_stream* pipe_stream;
+
     /**
      * Graphical representation of the current scroll state.
      */