Add pmonitor() to make it easy to monitor popen objects.

examples/popen.py

@@ -1,30 +1,36 @@
 #!/usr/bin/python
 
 """
-This example tests the Host.popen()/pexec() interface
+This example monitors a number of hosts using host.popen() and
+pmonitor()
 """
 
 from mininet.net import Mininet
 from mininet.node import CPULimitedHost
 from mininet.topo import SingleSwitchTopo
 from mininet.log import setLogLevel
-# from mininet.cli import CLI
-from mininet.util import custom
+from mininet.util import custom, pmonitor
 
-def testpopen(sched='cfs'):
-    "Test popen() interface"
-    host = custom( CPULimitedHost, cpu=.2, sched=sched )
-    net = Mininet( SingleSwitchTopo( 2 ), host=host )
+def monitorhosts( hosts=5, sched='cfs' ):
+    "Start a bunch of pings and monitor them using popen"
+    mytopo = SingleSwitchTopo( hosts )
+    cpu = .5 / hosts
+    myhost = custom( CPULimitedHost, cpu=cpu, sched=sched )
+    net = Mininet( topo=mytopo, host=myhost )
     net.start()
-    h1 = net.get( 'h1' )
-    # CLI(net)
-    out, err, code = h1.pexec( 'ifconfig' )
-    print 'stdout:', out.strip()
-    print 'stderr:', err.strip()
-    print 'exit code:', code
+    # Start a bunch of pings
+    popens = {}
+    last = net.hosts[ -1 ]
+    for host in net.hosts:
+        popens[ host ] = host.popen( "ping -c5 %s" % last.IP() )
+        last = host
+    # Monitor them and print output
+    for host, line in pmonitor( popens ):
+        if host:
+            print "<%s>: %s" % ( host.name, line.strip() )
+    # Done
     net.stop()
 
 if __name__ == '__main__':
     setLogLevel( 'info' )
-    testpopen('rt')
-    testpopen('cfs')
+    monitorhosts( hosts=5 )