shell判断结构和循环结构

一、判断结构

1. if判断结构

   if expression; then

      command1

      command2

   fi

2. if/else判断结构

   if expression; then

       command

   else

      command

   fi

3. if/elif/else判读结构

   if expression; then

       command

   elif expression; then

      command

   elif expression; then

      command

   …

   fi

4. case结构

   case VAR in

   var1) command1 ;;

   var2) command2 ;;

   …

   *）command ；；

   esac

二、循环结构

1、for循环

    for variable in(list)

    do

        command

    done

2、类C的for循环

    for((expression1;expression2;expression3))

    do

        command

    done

3、while循环

    while expression

    do 

        command

    done

4、until循环

    until expression

    do

        command

    done

5、select循环

    select MENU in (list)

    do

        command

    done