[Winpcap-users] Output to Cygwin Terminal (mintty) appears queued

inetjunkmail inetjunkmail at gmail.com
Mon Jan 9 05:51:15 PST 2012

I use Cygwin on Windows 7 64-bit.  In the past few months, Cygwin
shifted from running within cmd.exe to their own terminal based off of
Putty which they call mintty.  In my opinion, it's far superior in
every way so I use it exclusively.  Since tcpdump is not ported to
Cygwin, I run WinDump within the mintty terminal.  The problem is that
output appears to be queued and periodically flushed rather than
streaming like it does when run from cmd.exe.  If I start a ping going
to a host then run windump -i1 -n 'icmp' I immediately start seeing
the pings in a cmd.exe window but fail to see anything for about 20
seconds in the mintty terminal.  Then, all 20 seconds worth of data is
displayed followed by another pause, followed by another dump, etc.

I reached out to the Cygwin list and was told:

"From the point of view of these programs, mintty is a pipe. When a
program thinks it's writing to a display (a tty), it typically flushes
the output after every line. But when a program thinks the user won't
see its output, a program typically flushes its buffers less often
because writing in larger chunks is more efficient. You need to
convince these non-Cygwin programs to not buffer their output."

Are there any switches I can use when I run WinDump to alleviate this?
 If not, is there any other recommendation?

Thanks, Eric

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