利用tcpdump截获msn信息

 #!/bin/sh
echo "" > temp.1
echo "" > temp.3

#此处没有限制多少个msn数据包

tcpdump -f -lnx -s 0 host 192.168.0.1 and port 1863 > temp.0
lines=`cat temp.0 | wc -l`
line=1
while [ $line -le $lines ]
do

#此处获取时间收发ip等信息

memo=`sed -n ''"$line"'p' temp.0 | gawk '{if (!~/^0x/)print ,,,,,,,,,,," "}'`
memo=$"aaaaaaaa"
if [ "$memo" = "aaaaaaaa" ]
then

#截取数据包中数据部分

out=`sed -n ''"$line"'p' temp.0 | cut -c"11-14, 16-19, 21-24, 26-29, 31-34, 36-39, 41-44, 46-49"`
echo -n "$out" >> temp.1
else
echo "" >> temp.1
out=`sed -n ''"$line"'p' temp.0 | gawk '{if (!~/^0x/)print ,,,,,,,,,,," "}'`
echo -n "$out" >> temp.1
fi
line=`expr $line + 1`
done
echo "" >> temp.1

#删除空行和前两行

sed '/^&/d' temp.1 | sed '1,2d' > temp.2
lines=`cat temp.2 | wc -l`
line=1
while [ $line -le $lines ]
do

#获取要现实的内容
TIME=`sed -n ''"$line"'p' temp.2 | gawk '{print }' | gawk -F "." '{print }'`
FROM=`sed -n ''"$line"'p' temp.2 | gawk '{print }'`
TO=`sed -n ''"$line"'p' temp.2 | gawk '{print }'`

#根据标志位确定并截取msn数据

DATA0=`sed -n ''"$line"'p' temp.2 | awk '{print }' | gawk -F "0d0a0d0a" '{print }' | sed '/^0d0a$/d' | sed 's/../%&/g'`

#将截获的utf-8十六进制数交由perl的URI::Escape模块处理并显示中英文

DATA=`perl -e "use URI::Escape; print uri_unescape('$DATA0');"`
isnull=`echo $DATA | wc -m`
if [ $isnull -gt 1 ]
then
echo "$ FROM $ TO $ DATA: $"
fi
line=`expr $line + 1`
done
rm -f temp.*