shell脚本小示例

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求1-100自然数的和：   法一：for循环 #!/bin/bash # declare -i sum=0 for ((i=0;i<=100;i++));do   let sum+=$i done   echo "Sum:$sum"   法二：while循环 #!/bin/bash # declare -i sum=0 declare -i i=0   while [ $i -le 100 ];do   let sum+=$i   let i++ done echo $i echo "Summary:$sum."   统计tcp连接状态的脚本：   #!/bin/bash # This script is count tcp status   declare -i estab=0 declare -i listen=0 declare -i other=0   for state in $(netstat -tan | grep "^tcp\>" | awk "{print $NF}");do   if [ "$state" == 'ESTABLISHED' ];then     let estab++   elif [ "$state" == 'LISTEN' ];then     let listen++   else     let other++   fi   done   echo "ESTABLISHED:$estab" echo "LISTEN:$listen" echo "Unknow:$other"   批量添加10个用户：   #!/bin/bash   if [ ! $UID -eq 0 ];then   echo "Only root can use this script."   exit 1 fi   for i in {1..10};do   if id user$i &> /dev/null;then     echo "user$i exist"   else     useradd user$i     if [ $? -eq 0 ];then       echo "user$i" | passwd --stdin user$i &> /dev/null     fi   fi   done   测试一个网段内主机的连通脚本：   #!/bin/bash #ping   net='172.16.1' uphosts=0 downhosts=0   for i in {1..254};do   ping -c 1 -w 1 ${net}.${i} &> /dev/null   if [ $? -eq 0 ];then     echo "${net}.${i} is up."     let uphosts++   else     echo "${net}.${i} is down."     let downhosts++   fi done   echo "Up hosts:$uphosts" echo "Down hosts:$downhosts"   求数的阶乘：   #!/bin/bash #   fact() {     if [ $1 -eq 0 -o $1 -eq 1 ];then     echo 1   else     echo $[$1*$(fact $[$1-1])]   fi   }   fact 5