wlan-nav

柯老师网站上找到的

#!/bin/tcsh
#
# Channel utilization:
# works on a trace file produced by ns
# outputs idle time and the collision time on the channel between
# the first and the (possibly unfinished) last transmission
# for now: assumes that all MACs are on a single channel

if ( $#argv != 1 ) then
  echo usage:
  echo "      " $0 \<scenario\>
  exit 1
endif

set scenario = $1
set tracefile = $scenario.tr
set outfile = $scenario.nav
rm -f $outfile

egrep "\-Nl MAC " $tracefile | gawk -v outfile=$outfile '{				\
	if (($1 == "x") && ($29 == "BEACON")) {						\
		print $3, 0.0 >> outfile;						\
		print $3, 1.0 >> outfile;						\
		nav = 1;								\
	}										\
	if ((nav == 1) && ($1 == "s")) {						\
		print $3, 1.0 >> outfile;						\
		print $3, 0.0 >> outfile;						\
		nav = 0;								\
	}										\
}'