shell脚本练习2——循环语句（for、while、until循环等的应用）

2021/7/19 7:09:10

编程Tag： 循环 bash do while shell echo sum 100 bin

本文主要是介绍shell脚本练习2——循环语句（for、while、until循环等的应用），对大家解决编程问题具有一定的参考价值，需要的程序猿们随着小编来一起学习吧！

1.计算从1到100所有整数的和

#/bin/bash
#Calculate the sum of all integers from 1 to 100

a=1
sum=0
while [ $a -le 100 ]
do
  sum=$[$a+$sum]
  let a++
done
  echo "1到100的和为：$sum"

#/bin/bash
#Calculate the sum of all integers from 1 to 100


sum=0
for ((i=1;i<=100;i++))
do
    sum=$[ $i + $sum ]
done
    echo "1到100的和为为:$sum"

2.提示用户输入一个小于100的整数，并计算从1到该数之间所有整数的和

#!/bin/bash
#Prompts the user to enter an integer less than 100 and calculates the sum of all integers from 1 to that number  


read -p "请输入一个小于100的整数：" num
sum=0
for ((i=1;i<=$num;i++))
do
   sum=$[$sum+$i]
done
   echo "1到$num的和为：$sum"

#!/bin/bash
#Prompts the user to enter an integer less than 100 and calculates the sum of all integers from 1 to that number  


read -p "请输入一个小于100的整数：" num
sum=0
a=1
#while [ $a -le $num ]
until [ $a -gt $num ]
do
   sum=$[$sum+$a]
   let a++
done
   echo "1到$num的和为：$sum"

3.求从1到100所有整数的偶数和、奇数和

#!/bin/bash
# Fineven and odd sums of all integers from 1 to 100 

sum1=0
sum2=0
for ((i=1;i<=100/2;i++))
do
   a=$[2*$i]
   b=$[(2*$i)-1]
   sum1=$[ $sum1 + $a]
   sum2=$[ $sum2 +$b ]
done
   echo "偶数和为:$sum1"
   echo "奇数和为:$sum2"

#!/bin/bash
# Fineven and odd sums of all integers from 1 to 100 

a=1
sum1=0
sum2=0
while [ $a -le 100 ]
#until [ $a -gt 100 ]
do
   if [ $[ $a % 2] -eq 0 ];then
   sum1=$[ $sum1 + $a ]
   else
   sum2=$[ $sum2 + $a ]
   fi
   let a++
done
    echo "偶数和为:$sum1"
    echo "奇数和为:$sum2"

4.执行脚本输入用户名，若该用户存在，输出提示该用户已存在；若该用户不存在，提示用户输入密码，建立用户并设立其密码

#!/bin/bash
#Execute the script to enter the user name

read -p "请输入用户名：" username

if grep "$username:" /etc/passwd > /dev/null
then
   echo "$username 已存在"
else
   useradd $username
   read -p "请设置该用户密码：" password
   echo "$password"|passwd --stdin $username
fi

#!/bin/bash
#Execute the script to enter the user name

read -p "请输入用户名：" username

id $username &> /dev/null
if [ $? -eq 0 ]
then
   echo "$username 已存在"
else
   useradd $username
   read -p "请设置该用户密码：" password
   echo "$password"|passwd --stdin $username
fi

5.检测指定范围主机是否通信，并将通信的主机ip输出到文件host_ip中

#!/bin/bash
#Detects whether the host in the specified range is communicating

for i in 192.168.229.{59..62}
do
  ping -c 3 -i 0.5 -w 2 $i &> /dev/null
  if [ $? -eq 0 ]
  then
     echo "$i" >> host_ip.txt
     echo "$i is online"
  else
     echo "$i is offline"
  fi
done

多线程操作（for循环）

#!/bin/bash
#Detects whether the host in the specified range is communicating

for i in 192.168.229.{1..255}
do
{
  ping -c 3 -i 0.5 -w 2 $i &> /dev/null
  if [ $? -eq 0 ]
  then
     echo "$i" >> host_ip.txt
     echo "$i is online"
  else
     echo "$i is offline"
  fi
}&
done
   wait
   cat /root/host_ip.txt

wait是等待前面的后台任务全部完成才往下执行，否则程序本身是不会等待的，这样对后面依赖前面任务结果的命令来说就可能出错

6.用户输入密码，脚本判断密码是否正确，输入正确提示正确信息，连续输错3次则报警

#!/bin/bash
#Determine if the password was entered correctly

read -p "请输入密码：" first

for i in {1..3}
do
   read -p "请再次输入密码：" second
   if [ $first == $second ]
   then
      echo "输入的密码正确！"
      exit
   else
      echo "输入的密码有误！"
   fi
done
echo "错误次数过多，退出程序！"

7.编写能够自动生成一个8位随机密码的脚本

#!/bin/bash
#Automatically generates an 8-digit random password

Str="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890"

for i in {1..8}
do

  num=$[ $RANDOM % ${#Str}]
  tmp=${Str:num:1}
  password+=$tmp

done
  echo "自动生成的随机密码为：$password"

8.写个逛淘宝选购商品脚本，每家商店有五种商品选购（衣服800元，裤子600元，鞋子900元，内衣300元，袜子100元），每次选购完或不买都会提示用户是否继续逛下一家商店，如果不再继续逛的话进行购物车结算总额。

#!/bin/bash
#Shopping Goods

i=1
a=0
sum=0
while [ $a -eq 0 ]
do
  echo "欢迎来到第$i家店！"
  read -p "是否要进店选购商品(yes/no): " going
  while [ $going == "yes" ]
  do
    echo -e "1:衣服800元 \n2:裤子600元 \n3:鞋子900元 \n4:袜子100元 \n5:内衣300元 \n6:放弃选购"
    read -p "请输入你选择的商品序号：" num
    case $num in
    1)
      echo "衣服选购成功！"
      sum=$[$sum + 800]
    ;;
    2)
      echo "裤子选购成功！"
      sum=$[$sum + 600]
    ;;
    3)
      echo "鞋子选购成功！"
      sum=$[$sum + 900]
    ;;
    4)
      echo "袜子选购成功！"
      sum=$[$sum + 100]
    ;;
    5)
      echo "内衣选购成功！"
      sum=$[$sum + 300]
    ;;
    6)
      echo "放弃选购"
    ;;
    *)
      echo "输入错误，没有此选项！"
    esac
    read -p "是否再继续选购（yes/no）: " going
  done
    read -p "是否再继续逛下一家店（yes/no）: " doing
  if [ $doing == "yes" ];then
     let i++
  else
    echo -e "谢谢惠顾！\n您一共逛了$i家店。\n您一共消费了$sum元。"
    exit
  fi
done

9、输出环境变量PATH 的目录所包含的可执行文件

#/bin/bash
#The executable file contained in the directory that outputs the environment variable PATH

OLDIFS=$IFS
IFS=$IFS":"
for i in $PATH
do
  echo $i
  cd $i
  for f in $(ls $i)
  do
    if [ -x $f ];then
   #if [ -x $i/$f];then
      echo "---$i/$f"
    fi
  done
done
IFS=$OLDIFS

#/bin/bash
#The executable file contained in the directory that outputs the environment variable PATH

OLDIFS=$IFS
IFS=$IFS":"
for i in $PATH
do
  echo $i
  for f in $i/*
  do
    if [ -x $f ];then
      echo "---$f"
    fi
  done
done
IFS=$OLDIFS

10、mkdir -p /root/bin/aa/bb/cc/dd ; touch /root/bin/aa/bb/cc/dd/abc.txt，输出环境变量PATH所包含的所有目录以及其中的子目录和所有不可执行文件

#!/bin/bash
#Output all directories contained in the environment variable PATH along with subdirectories and any non-executable files  

OLDIFS=$IFS
IFS=$IFS":"
for i in $PATH
do
  echo "$i:"
  Dir=$(find $i -type d)
  for d in $Dir
  do
   echo $d
  done
  file=$(find $i -type f)
  for f in $file
  do
    if [ ! -x "$f" ];then
    echo "---$f"
  fi
  done
done

IFS=$OLDIFS