[nSLUG] April Tech Talk
nslug at fop.ns.ca
Wed Apr 22 15:46:26 ADT 2015
On Wed, 22 Apr 2015, Mike Spencer wrote:
> If I pipe tcpdump through " | tee logfile", output from tcpdump gets
> buffered up somewhere. Both the stdout and the logfile get updated in
> spurts that may break the tcpdump output in the middle of a line.
I think you may want "tcpdump -l". Checking the man page on a local
machine this exact scenario is actually listed, coincidentally enough:
" -l Make stdout line buffered. Useful if you want to see the data while
capturing it. E.g.,
tcpdump -l | tee dat
tcpdump -l > dat & tail -f dat
Note that on Windows,``line buffered'' means ``unbuffered'', so that
WinDump will write each character individually if -l is specified.
-U is similar to -l in its behavior, but it will cause output to be
``packet-buffered'', so that the output is written to stdout at the end of
each packet rather than at the end of each line; this is buffered on all
platforms, including Windows."
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