I find the root cause: shouldn’t use & after “iftop -nt”,because “&”  tells bash to fork again.After I test,it’s OK.

From: iftop-users-admin@lists.beasts.org [mailto:iftop-users-admin@lists.beasts.org] On Behalf Of Darren (Chenji) Xu
Sent: Wednesday, February 12, 2014 2:17 PM
To: iftop-users@lists.beasts.org
Subject: [Iftop-users] the CPU usage is 100% when shell or perl script run iftop

Hi Paul,

Do you encounter this issue? I haven’t found this issue when I used tcpdump.

I think it maybe a iftop bug.

Thanks,

Darren

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PS:

#!/bin/bash

#tcpdump -nnlqp tcp &

iftop -nt &