linux shell常用循环与判断语句(for，while，until,if)使用方法

#!/bin/bash 
 
for file in $(ls /tmp/test/mytest |grep sh)  //for in格式是shell for的基本格式，根js的for in类似 
do        //循环开始你就把它当成{ 
 echo $file 
done       //循环结束你就把它当成} 
 
for ((i=0;i<10;i++))    //注意是双小括号，由于受其他语言的影响，很容易搞错 
do 
 echo -n $i 
done 
 
echo \   //输出换行 
 
for i in 0 1 2 3 4 5 6 7 8 9 
do 
 echo -n $i 
done 
 
echo \ 
 
for i in "0 1 2 3 4 5 6 7 8 9"  //这个根上面是有区别的，这个循环只循环了一次，双引号里面只是一个变量 
do 
 echo -n $i 
done 
 
exit 0 

#!/bin/bash 
i=0 
while ((i<10)) 
do 
 echo $i 
 ((i += 1)) 
done 
 
i=0 
while [ $i -lt 10 ] //注意括号内侧二边的空格 
do 
 echo $i 
 let "i+=1"  //加1 
done 
exit 0 

#!/bin/bash 
 
END_CONDITION=end 
until [ "$var1" = "$END_CONDITION" ] //读取的变量根设定的变量相等时退出循环，不然永远循环 
do 
 echo "Input variable #1 " 
 echo "($END_CONDITION to exit)" 
 read var1 
 echo "variable #1 = $var1" 
 echo 
done  
exit 0 

#!/bin/bash 
 
echo "Input a number #1 " 
read num 
echo "variable #1 = $num" 
 
if [ $num -lt 60 ]  //注意lt前面的-，很容易忘的 
then 
 echo "you are not pass" 
elif [ $num -lt 70 ] && [ $num -ge 60 ] //多个条件的判断 
then 
 echo "pass" 
elif [[ $num -lt 85 && $num -ge 70 ]] //如果放在一起，要注意是双方括号，不要写成[ $num -lt 85 && $num -ge 70 ] 
then 
 echo "good" 
elif (( $num <= 100 )) && (( $num >= 85 )) //对于有语言基础的人来说，这种写法让人觉得很舒服，不要忘了是双小括号 
then 
 echo "very good" 
else 
 echo "num is wrong" 
fi                 //if要有结束标签的，根XML很像,不闭合，就报错 
 
exit 0

#!/bin/sh 
case $1 in 
 start) 
 echo "start ok" 
 ;;    //注意一点，要注意是双分号 
 stop) 
 echo "stop ok" 
 ;; 
 restart) 
 echo "restart ok" 
 ;; 
 *) 
 echo "no param" 
 ;; 
esac   //注意闭合标签 
exit 0 
 
[root@krlcgcms01 forif]# sh c1.sh stop 
stop ok