Shell中的while循環(huán)幾種使用實例詳解

#!/bin/bash
i=1
sum=0
while [ $i -le 100 ]
do
 let sum=sum+$i
 let i++
done
echo $sum

#!/bin/bash
i=1
sum=0
while [ $i -le 100 ]
do
 let sum=sum+$i
 let i+=2
done
echo $sum

#!/bin/bash
i=2
sum=0
while [ $i -le 100 ]
do
 let sum=sum+$i
 let i+=2
done
echo $sum

#!/bin/bash
i=1
j=1
while [ $i -le 5 ]
do
 while [ $j -le 5 ]
 do
   echo -n "* "
   let j++
 done
 echo
 let i++
 let j=1
done

#!/bin/bash
file=$1         #將位置參數(shù)1的文件名復制給file
if [ $# -lt 1 ];then   #判斷用戶是否輸入了位置參數(shù)
 echo "Usage:$0 filepath"
 exit
fi
while read -r line  #從file文件中讀取文件內(nèi)容賦值給line（使用參數(shù)r會屏蔽文本中的特殊符號，只做輸出不做轉(zhuǎn)譯）
do
 echo $line    #輸出文件內(nèi)容
done   $file

#!/bin/bash
file=$1
if [[ $# -lt 1 ]]
then
 echo "Usage: $0 please enter you filepath"
 exit
fi
while read -r f1 f2 f3  #將文件內(nèi)容分為三列
do
 echo "file 1:$f1 ===> file 2:$f2 ===> file 3:$f3"  #按列輸出文件內(nèi)容
done  "$file"

#!/bin/bash
#打印菜單
while :
do
 echo "********************"
 echo "    menu    "
 echo "1.tima and date"
 echo "2.system info"
 echo "3.uesrs are doing"
 echo "4.exit"
 echo "********************"
 read -p "enter you choice [1-4]:" choice
#根據(jù)客戶的選擇做相應(yīng)的操作
 case $choice in
  1)
  echo "today is `date +%Y-%m-%d`"
  echo "time is `date +%H:%M:%S`"
  read -p "press [enter] key to continue..." Key  #暫停循環(huán)，提示客戶按enter鍵繼續(xù)
  ;;
  2)
  uname -r
  read -p "press [enter] key to continue..." Key
  ;;
  3)
  w
  read -p "press [enter] key to continue..." Key
  ;;
  4)
  echo "Bye!"
  exit 0
  ;;
  *)
  echo "error"
  read -p "press [enter] key to continue..." Key
  ;;
 esac
done