[转] 6. Bourne Shell及shell编程

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        前9个参数之后的参数，就必须使用shift.
 
        另外shift后可加整数进行一次多个移位，如：
 
                shift 3
 
 
    <4>. for循环
       格式：
                for var in arg1 arg2 ... argn
                do
                        command
                        ....
                        command
                done
 
        示例：
        $ for letter in a b c d e; do echo $letter;done
        a
        b
        c
        d
        e
 
        对当前目录下的所有文件操作：
        $ for i in *
          do
                if [ -f $i ]
                then
                        echo "$i is a file"
                elif    [ -d $i ]
                        echo "$i is a directory"
                fi
          done
 
        求命令行上所有整数之和：
        #!/bin/sh
 
        sum=0
 
        for INT in $*
        do
                sum=`expr $sum + $INT`
        done
 
        echo $sum
 
 
      <6> 从循环中退出： break和continue命令
        break           立即退出循环
        continue        忽略本循环中的其他命令，继续下一下循环
 
        在shell编程中有时我们要用到进行无限循环的技巧，也就是说这种循环一直执行
碰
        到break或continue命令。这种无限循环通常是使用true或false命令开始的。UNIX
        系统中的true总是返加0值，而false则返回非零值。如下所示：
 
        #一直执行到程序执行了break或用户强行中断时才结束循环
        while true
        do
                command
                ....
                command
        done
 
        上面所示的循环也可以使用until false, 如下：
 
        until false
        do
                command
                ....
                command
        done
 
        在如下shell script中同时使用了continue,break以及case语句中的正规表达式用
法：
 
         #!/bin/sh
         # Interactive program to restore, backup, or unload
         # a directory
 
         echo "Welcome to the menu driven Archive program"
 
         while true
         do
         # Display a Menu
            echo
            echo "Make a Choice from the Menu below"
            echo _
            echo "1  Restore Archive"
            echo "2  Backup directory"
            echo "3  Unload directory"
            echo "4  Quit"
            echo
 
         # Read the user's selection
            echo -n "Enter Choice: "
 
            read CHOICE
 
            case $CHOICE in
               [1-3] ) echo
                       # Read and validate the name of the directory
 
                       echo -n "What directory do you want? "
                       read WORKDIR
 
                       if [ ! -d "$WORKDIR" ]
                       then
                          echo "Sorry, $WORKDIR is not a directory"
                          continue
                       fi
 
                       # Make the directory the current working directory
                       cd $WORKDIR;;
 
                    4) :;;    # :为空语句，不执行任何动作
                    *) echo "Sorry, $CHOICE is not a valid choice"
                       continue
            esac
 
            case "$CHOICE" in
               1) echo "Restoring...还有问题请来论坛寻求帮助：