Thanks for your reply. What I want is to flush the results of "sudo /usr/sbin/tcpdump -i $Interface host $Multicast 2>/dev/null |" to TCPDump. I tried "$| = 1" but it didn't work either. Any suggestion I can make the while loop to print the traffic at once? I tried the sudo command in a bash shell and I can see the results right away. However, the output of the sudo tcpdump feeding to TCPDump is batched in my Perl program. This causes the rest of the codes(removed here) to fail.

In reply to Re^2: Autoflush fails by sophate
in thread Autoflush fails by sophate

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