diff --git a/mininet/node.py b/mininet/node.py
index 842b0dc..b0a3951 100644
--- a/mininet/node.py
+++ b/mininet/node.py
@@ -212,7 +212,7 @@ class Node( object ):
     # Subshell I/O, commands and control
 
     def read( self, maxbytes=1024 ):
-        """Buffered read from node, non-blocking.
+        """Buffered read from node, potentially blocking.
            maxbytes: maximum number of bytes to return"""
         count = len( self.readbuf )
         if count < maxbytes:
@@ -227,7 +227,7 @@ class Node( object ):
         return result
 
     def readline( self ):
-        """Buffered readline from node, non-blocking.
+        """Buffered readline from node, potentially blocking.
            returns: line (minus newline) or None"""
         self.readbuf += self.read( 1024 )
         if '\n' not in self.readbuf:
@@ -259,9 +259,10 @@ class Node( object ):
 
     def waitReadable( self, timeoutms=None ):
         """Wait until node's output is readable.
-           timeoutms: timeout in ms or None to wait indefinitely."""
+           timeoutms: timeout in ms or None to wait indefinitely.
+           returns: result of poll()"""
         if len( self.readbuf ) == 0:
-            self.pollOut.poll( timeoutms )
+            return self.pollOut.poll( timeoutms )
 
     def sendCmd( self, *args, **kwargs ):
         """Send a command, followed by a command to echo a sentinel,
@@ -303,7 +304,9 @@ class Node( object ):
            Set self.waiting to False if command has completed.
            timeoutms: timeout in ms or None to wait indefinitely
            findPid: look for PID from mnexec -p"""
-        self.waitReadable( timeoutms )
+        ready = self.waitReadable( timeoutms )
+        if not ready:
+            return ''
         data = self.read( 1024 )
         pidre = r'\[\d+\] \d+\r\n'
         # Look for PID