使用tcpdump 对nginx的access.log 非400的ip进行自动抓包

#抓取nginx access日志不是 400 的行,找出该ip ,并且启动抓包
#该脚本的执行要放在 crond 里面或者 while循环里面
##################
#网卡名称
net_card=enp0s8
#最多抓取10条记录
cap_max_ip_num=1
#要抓取ip的在nginx里面的错误
#存放抓包的目录
cap_dir="/tmp/cap_dir/"
if [ ! -d "$cap_dir" ]; then
	mkdir "$cap_dir"
fi
#当前已经开始抓包的ip地址
cap_ip_history_file="$cap_dir/___tcp_dump_ip"
if [ ! -f "$cap_ip_history_file" ]; then
　　touch  "$cap_ip_history_file"
fi 
function mytcpdump()
{
	ip=$1
	tcpdump -i $net_card -w $cap_dir/file${ip}.cap host $1 &
}
function begin_capture()
{
    count_line=`wc -l $cap_ip_history_file | awk '{print $1}'`
    if [ $count_line -ge $cap_max_ip_num ];then
        echo " capture max limit !!"
	exit 1
    fi
	ip=`tail -1 access.log |awk '{if($(NF-4)==400) print $1}'`
	echo "access the log is " $ip
	if [ "$ip" != "" ]; then
		grep_result=`grep "$ip" $cap_ip_history_file `
		if [ "$grep_result" == "" ]; then
			echo "begin tcp dump " $ip
			echo `date` $ip >> $cap_ip_history_file
			mytcpdump $ip
		fi
	fi
}
function clean()
{
	rm -rf $cap_dir
}
case "$1" in
    start)
        begin_capture
        ;;
    clean)
        clean
        ;;
    *)
        echo $"Usage: $0 {start|clean}"
        exit 1
esac