shell迴圈loop

標籤：shell   loop   while   until   for   

1. 迴圈
shell迴圈，不斷執行某段程式，直到符合條件。迴圈分為4種， while迴圈，until迴圈，for固定處理， for數值處理。
2. while迴圈
while迴圈是一直執行，直到條件不符合，才停止。文法：while [ condition ]do//do somethingdone例： 迴圈直到使用者輸入正確

#!/bin/bash# desc : while loopwhile [ "$yn" != "yes" -a "$yn" != "YES" ] do     read -p "Please input yes/YES to stop : " yndoneecho "OK"

執行結果：

[[email protected] sh]$ sh while.sh Please input yes/YES to stop : noPlease input yes/YES to stop : yesOK[[email protected] sh]$ 

例：從1加到100

#!/bin/bash# desc : while loopsum=0i=0while [ $i -lt 100 ]do    i=$(($i+1));    sum=$(($sum+$i))doneecho "From 1 to 100, sum is : " $sum 

3. until迴圈
until迴圈和while相反，當條件condition成立時，終止迴圈。文法：until [ condition ]do//do somethingdone例：

#!/bin/bash# desc : while loopuntil [ "$yn" == "yes" -o "$yn" == "YES" ]do    read -p "Please input yes/YES to stop : " yndoneecho "OK"

執行：

[[email protected] sh]$ sh while.sh Please input yes/YES to stop : hi         Please input yes/YES to stop : yesOK[[email protected] sh]$ 

4. for固定迴圈
for為已知次數的迴圈。文法：for var in con1 con2 ..do//do somethingdone例：

#!/bin/bash# desc : for loopfor animal in dog cat pig do    echo "HI, ${animal}"done

執行：

[[email protected] sh]$ sh for.sh HI, dogHI, catHI, pig[[email protected] sh]$

例：目前的目錄檔案

#!/bin/bash# desc : for loopfilelist=$(ls)for filename in $filelistdo    echo $filenamedone

5. for數值迴圈
for數值迴圈，適用於迴圈數值計算。文法for (( 初始值; 限制值; 步長))do// do somethingdone例：

#!/bin/bash# desc : for loopsum=0for (( i=0; i<=100; i++ ))do    sum=$(($sum+$i))doneecho "sum is : " $sum

地址：http://blog.csdn.net/yonggang7/article/details/40679701

shell迴圈loop