# check a file to be a correct runlevel script
check_runlevel () #检测在脚本启动目录下的相关脚本,并且返回相应的值0|1
{
        # Check if the file exists at all.
        [ -x "$1" ] || return 1

        # Reject backup files and files generated by rpm.
        case "$1" in
                *.rpmsave|*.rpmorig|*.rpmnew|*~|*.orig)
                        return 1
                        ;;
        esac
        return 0
}

# Now find out what the current and what the previous runlevel are.
argv1="$1" #读取位置参数1
set `/sbin/runlevel` #创建位置参数
runlevel=$2
previous=$1
export runlevel previous #创建全局环境变量

. /etc/init.d/functions #载入函数

# See if we want to be in user confirmation mode
if [ "$previous" = "N" ]; then
        if [ -f /var/run/confirm ]; then
                echo $"Entering interactive startup"
        else
                echo $"Entering non-interactive startup"
        fi
fi

# Get first argument. Set new runlevel to this argument.
[ -n "$argv1" ] && runlevel="$argv1"#如果第一个参数不为空,那么就将其argv1这个变量赋值给变量 

                                  #runlevel

# Is there an rc directory for this new runlevel?
[ -d /etc/rc$runlevel.d ] || exit 0 #检测运行级别是否是否目录

# First, run the KILL scripts.
for i in /etc/rc$runlevel.d/K* ; do
        check_runlevel "$i" || continue

        # Check if the subsystem is already up.
        subsys=${i#/etc/rc$runlevel.d/K??} #这句话很有用,它是截取的作用,将符合#后面的文字都 

                                         #将其除去
        [ -f /var/lock/subsys/$subsys -o -f /var/lock/subsys/$subsys.init ] \
                || continue        #判定$sybsys与$subsys.init两个文件是否存在,若存在,那么什 

                                 #么都不做,若不存在,那么不执行下面的语句

        # Bring the subsystem down.
        if egrep -q "(killproc |action )" $i ; then
                $i stop
        else
                action $"Stopping $subsys: " $i stop
        fi
done

# Now run the START scripts.
for i in /etc/rc$runlevel.d/S* ; do
        check_runlevel "$i" || continue

        # Check if the subsystem is already up.
        subsys=${i#/etc/rc$runlevel.d/S??}
        [ -f /var/lock/subsys/$subsys -o -f /var/lock/subsys/$subsys.init ] \
                && continue

        # If we're in confirmation mode, get user confirmation
        if [ -f /var/run/confirm ]; then
                confirm $subsys
                test $? = 1 && continue
        fi

        update_boot_stage "$subsys"
        # Bring the subsystem up.
        if [ "$subsys" = "halt" -o "$subsys" = "reboot" ]; then
                export LC_ALL=C
                exec $i start
        fi
        if egrep -q "(daemon |action |success |failure )" $i 2>/dev/null \
                        || [ "$subsys" = "single" -o "$subsys" = "local" ]; then
                $i start
        else
                action $"Starting $subsys: " $i start
        fi
done
rm -f /var/run/confirm
if [ -x /usr/bin/rhgb-client ] && /usr/bin/rhgb-client --ping ; then
  /usr/bin/rhgb-client --quit
fi

===================
参考代码:
[No.501 19:04:23 ~]$ set var1 var2 var3
[No.502 19:04:37 ~]$ while (( $#>0 ));do
> echo $1
> shift
> done
var1
var2
var3
[No.503 19:05:07 ~]$ echo $#
0
[No.504 19:05:26 ~]$ set var1 var2 var3
[No.505 19:05:41 ~]$ echo $#
3
[No.506 19:05:44 ~]$ echo "$@"
var1 var2 var3
[No.507 19:05:54 ~]$ set --
[No.508 19:06:31 ~]$ echo $#
0
[No.509 19:06:35 ~]$ echo "$@"

[No.510 19:06:39 ~]$