netstat 指令

netstat 指令将所有的网络端口监听情况进行罗列

语法  netstat -tuln

几个常见的服务端口

例  通过grep 查看端口来获得上面的服务是否开启，并给予提示

  1 #!/bin/bash
  2 #Program:
  3 #       Using netstat and grep to detect WWW,SSH,FTP and Mail service
  4 #History:
  5 #2019-7-29  lsq First release
  6 PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:~/bin
  7 export PATH
  8 
  9 #tell some action
 10 echo "Now, I will detect your linux server's services !"
 11 echo -e "The www,ftp,ssh,and mail(smtp) will be detect! 
"
 12 
 13 #start some detect work ,to echo some information
 14 testfile=/dev/shm/netstat_checking.txt
 15 netstat -tuln > ${testfile}
 16 testing=$(grep ":80 " ${testfile})
 17 if [ "${testing}" != "" ]; then
 18         echo "www is running in your system."
 19 fi
 20 
 21 testing=$(grep ":22" ${testfile})
 22 if [ "${testing}" != "" ]; then
 23         echo "SSH is running in your system"
 24 fi
 25 
 26 testing=$(grep ":21" ${testfile})
 27 if [ "${testing}" != "" ]; then
 28         echo "FTP is runing in your system"
 29 fi
 30 
 31 testing=$(grep ":25" ${testfile})
 32 if [ "${testing}" != "" ]; then
 33         echo "Mail is runing in your system"
 34 fi

上面的例子有几个坑，需要注意一下

第一个 还是空格问题。

testing=$(grep ":22" ${testfile})

=号前后没有空格，切记。

第二个 if [  ] 括号中前后需要有两个空格

第三个 if中 

"${testing}" != ""

！=前后都有空格

第四个 解析

上面例子的意思，用netstat -tuln命令将机器所有的服务端口信息保存到/dev/shm/netstat_checking.txt文件中

然后用grep针对端口进行查找，然后在分类输出。原理比较简单，就是那些坑，要注意，否则容易报错。