[shell基础]——if/for/while/until/case 语句

for语句

for loop in 1 2 3 4 5
do
  echo $loop
done

for loop in `seq 1 100`
do
  echo $loop
done


for loop in `ls /tmp`
do
   echo $loop
done

 

while语句

while true
do
   read -p "请输入你的密码:"  passwd
   if [ $passwd = "aixocm" ]
   then
       echo "密码输入正确,welcome"
       break
   else
       echo "密码输入错误"
       continue
   fi
done  

 

until语句

use=`df -lh | sed -n  '/\/$/{p}' | awk '{print $5}' |sed 's/%//g'`

#如果/使用率满足小于80%的条件,则不执行循环,
#反之若/大于80%(即不满足条件),则执行循环
until [ $use -lt 80 ]   
do
   echo "warning:your / user 80%" #向用户提出警告,你的/使用率已经大于或等于80%
   exit 1
done

#而是执行循环外的这条,
#告诉用户,你的/使用率是多少,还少于80%
echo "now your / use $use%,less then 80%"

 

case语句

function directory()
{
     [ -d  $1 ]
     if [ $? -eq 0 ]
     then
     echo "$1存在"
     else
     echo "$1不存在"
     fi
}

tput bold   --->#加粗
echo "===查询菜单==="
tput sgr0

echo "1、查询/opt/aa 目录是否存在?"
echo "2、查询/opt/cc 目录是否存在?"
echo "3、查询/opt/dd 目录是否存在?"
read -p  "你想查询啥?:" n
case $n in
    1) 
       directory /opt/aa
       ;;
    2)
       directory /opt/cc
       ;;
    3)  
       directory /opt/dd
       ;;
    *)
       echo error
       ;;
esac

 

if语句

#if/else结构
if
expression then command else command fi

#if/elif/else结构
if
 expression1
then
command
elif expression2
then command
elif
expression3
then command
else
command
fi

 

循环控制符:break和continue

break:忽略循环体中任何语句和条件的限制,强制退出当前循环
continue:跳过continue后面的语句,执行下一次循环,直到条件为真

posted @ 2016-07-26 17:46  Jelly_lyj  阅读(175)  评论(0编辑  收藏  举报