发个检测端口是否开启的小脚本！

这个小脚本可以检测WWW,ftp,ssh,sendmail + pop3服务是否开启：
#!/bin/bash
#program: Using to study the [ if ... then ... fi ] program
#dsk 2007/10/8 3:00
#content: I will using this program to show you sevices
#1. print the program's work in your screen
echo "Now, the service of your Linux system will be detect!"
echo "The www, ftp,ssh,and sendmail + pop3 will be detect!"
echo " "
#2. www
www='netstat -an|grep LISTEN|grep :80'
if [ "$www" != "" ]; then
echo "WWW is runing"
else
echo "WWW is NOT runing"
fi
#3. ftp
ftp='netstat -an|grep LISTEN|grep :21'
if [ "$ftp" != "" ]; then
echo "FTP is runing"
else
echo "FTP is not runing"
fi
#4. ssh
ssh='netstat -an|grep LISTEN|grep :22'
if [ "$ssh" != "" ];then
echo "SSH is running"
else
echo "SSH is not running"
fi
#5. sendmail + pop3
smtp='netstat -an|grep LISTEN|grep :25'
pop3='netstat -an|grep LISTEN|grep :110'
if [ "$smtp" != "" ] && [ "$pop3" != "" ]; then
echo "Sendmail is OK!"
elif [ "$smtp" != "" ] && [ "$pop3" = "" ]; then
echo "Sendmail have some problems of your pop3!"
elif [ "$smtp" = "" ] && [ "$pop3" != "" ]; then
echo "Sendmail have some problems of your smtp!"
else
echo "Sendmail is NOT running!"
fi