一、ls -l 默认排序顺序是从 0 到 9,从 a 到 z，ls -r是倒序。

 二、脚本里面通过for i in /etc/init.d/S??* ;do查看。

 三、在Linux系统目录/etc/init.d/下面有两个脚本程序rcS和rcK。rcS是系统开机后执行的脚本，名称中的"S"是"Start"的意思；rcK是系统收到关机命令后执行的脚本，名称中的"K"是"Kill"的意思；查看/etc/init.d/rcS 里面会执行启动脚本，文件里面的数字number决定执行的顺序.S后面的数字表示启动的顺序，数字小的先启动。比如"S20urandom"会比"S99_auto_reboot"先启动；

/etc/init.d #
/etc/init.d # cat rcS
#!/bin/sh


# Start all init scripts in /etc/init.d
# executing them in numerical order.
#
for i in /etc/init.d/S??* ;do

     # Ignore dangling symlinks (if any).
     [ ! -f "$i" ] && continue

     case "$i" in
        *.sh)
            # Source shell script for speed.
            (
                trap - INT QUIT TSTP
                set start
                . $i
            )
            ;;
        *)
            # No sh extension, so fork subprocess.
            $i start
            ;;
    esac
done

/etc/init.d #

/etc/init.d # cat rcK
#!/bin/sh


# Stop all init scripts in /etc/init.d
# executing them in reversed numerical order.
#
for i in $(ls -r /etc/init.d/S??*) ;do

     # Ignore dangling symlinks (if any).
     [ ! -f "$i" ] && continue

     case "$i" in
        *.sh)
            # Source shell script for speed.
            (
                trap - INT QUIT TSTP
                set stop
                . $i
            )
            ;;
        *)
            # No sh extension, so fork subprocess.
            $i stop
            ;;
    esac
done

/etc/init.d #

参考文章

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