循环脚本编写

#!/bin/bash
cd /var
File=`ls /var`
for i in *; do
   file_type=`ls -ld $i |cut -b1`
   case $file_type in
   d)
   echo "$i is 目录"
   ;;
   l)
   echo "$i is 链接文件"
   ;;
   -)
   echo "$i is 普通文件"
   ;;
   b)
   echo "$i is 设备文件"
   ;;
   c)
   echo "$i is 字符文件"
   ;;
   esac

done

#!/bin/bash
for i in {1..10}; do
    id user$i &>/dev/null && echo "user$i is  exit" || useradd user$i
    User_passwd=`echo $RANDOM |md5sum | cut -c 1-8`
    echo user$i:$User_passwd | chpasswd
    echo "user$i $User_passwd">>a.txt
done
bug 如果账户存在会将密码重置，建议增加一次判断，替换成 id user$i &>/dev/null && { echo "user$i is  exit";continue; },不能使用（），（）开启子

#!/bin/bash
mkdir testdir
cd testdir
for ((i=1;i<=10;i++));do
   file_name=`openssl rand -base64 20 | sed -nr "s/[^a-Z]+//gp" | cut -c 1-8`
   touch $i$file_name.html
done

#!/bin/bash
i=1
while [ $i -lt 10 ];do
  j=1
  while [ $j -le $i ];do
  echo -e "$i*$j=$[$i*$j]tc"
  let j++
  done
  echo 
let i++
done

#!/bin/bash
i=1
while [ $i -le 10 ] ;do
   ran=`openssl rand -base64 20 | cksum |cut -c 1-8`
   echo $ran >>a.txt
   if [ $i -eq 1 ];then
   max=$ran
   min=$ran
   else
     if [ $ran -ge $max ];then
       max=$ran
     elif [ $ran -le $min ];then
       min=$ran
     fi
   fi
let i++
done
echo "max=$max min=$min"

#!/bin/bash
cat a.txt | while read rand;do
{ while true;do
random=$RAMDOM
temp=`echo $random | md5sum | cut -c 1-10`
if [ "$ran" = "$temp" ];then
  echo "$rand is $random md5"
  break
fi
done }&
wait
done

#!/bin/bash
let NUM=$RANDOM%10
while read -p "请猜数字:" Guess ;do
  if [ $Guess -lt $NUM ];then
     echo "猜小了"
  elif [ $Guess -gt $NUM ];then
    echo "猜大了"
  else
    echo "猜对了，是$NUM"
    break
   fi
done

#!/bin/bash
sum=0
while [ -n "$1" ];do
line=`wc -l $1 | grep -o "[0-9]+"`
echo $1 $line
let sum+=line
shift
done
echo $sum