android的启动脚本(init.rc)文件的语法，参考资料：
Android 初始化语言(Android Init Language)
Android初始化脚本语言包含四种类型的语句：
动作(Actions)
指令(Commands)
服务(Services)
选项(Options)
该语言的语法包括下列约定：
所有类型的语句都是基于行(line-oriented)的，
一个语句包含若干个tokens，token之间通过空格字符分隔.
如果一个token中需要包含空格字符，则需要通过C语言风格的反斜线('\')来转义，或者使用双引号把整个token引起来。反斜线还可以出现在一行
的末尾，表示下一行的内容仍然属于当前语句。
以'#'开始的行是注释行。
动作(Actions)和服务(Services)语句隐含表示一个新的段落
(section)的开始。
所有的指令(commands)和选项(options)归属于上方最近的一个段落。在第一个段落之前的指令(commands)和选项
(options)是无效的。
动作(Actions)和服务(Services)拥有唯一性的名字。如果出现重
名，那么后出现的定义将被作为错误忽略掉。动作
(Actions)
动作(Actions)是一个有名字的指令(commands)序列。每个动作
(Actions)都定义一个触发条件(trigger)，用于指示什么时候执行这个动作。当与动作的触发器匹配的事件发生时，该动作将被添加到一个即将
被执行的队列的队尾(除非它已经在队列中)。
队列中的每一个动作被依次取出执行，动作中的每一个指令也将依次执行。初始化程序
(Init)在执行一个动作的各项指令的期间，还需要处理其它操作(比如，设备创建/销毁，属性设置，进程重启)。
一个动作定义的形式如下：on
服务(Services)服务是初始化程序需要启动的一些程序，初始化程序还有可能会在这些程序退出之后重启它们。
Services take 一个服务定义的形式如下：service [ ]*
...
选项(Options)
选项将影响控制初始化程序运行服务的时机和方法。可能的选项如下表。
选项
说明
disabled
This service will not automatically
start with its class. It must be explicitly started by name.
socket[ [ ]
]
Create a unix domain socket named /dev/socket/
and pass its fd to the launched process. Valid
values include dgram and stream. user
and group default to 0.
user
Change to username before exec'ing
this service. Currently defaults to root.
group [
]*
Change to groupname before exec'ing
this service. Additional groupnames beyond the first, which is
required, are used to set additional groups of the process (with setgroups()).
Currently defaults to root.
capability [ ]+
Set linux capability before exec'ing
this service
oneshot
Do not restart the service when it
exits.
class
Specify a class name for the service.
All services in a named class must start and stop together. A service
is considered of class "default" if one is not specified via the class
option.
触发器(Triggers)
触发器是一个字符串，用于匹配特定的事件，这些事件将触发触发器所属动作
(Actions)的执行。
触发器
说明
boot
This is the first trigger that occurs
when init starts (after /init.conf is loaded).
=
Triggers of this form occur when the
property is set to the specific value .
device-added-device-removed-
Triggers of these forms occur when a
device node is added or removed.
service-exited-
Triggers of this form occur when the
specified service exits.
指令(Commands)
Command
Description
exec [
]*
Fork and execute a program ().
This will block until the program completes execution. Try to avoid
exec. Unlike the builtin commands, it runs the risk of
getting init "stuck".
export
Set the environment variable
equal to in the global environment (which
will be inherited by all processes started after this command is
executed).
ifup
Bring the network interface
online.
import
Parse an init config file, extending
the current configuration.
hostname
Set the host name.
class_start
Start all services of the specified
class if they are not already running.
class_stop
Stop all services of the specified
class if they are currently running.
domainname
Set the domain name.
insmod
Install the module at .
mkdir
Make a directory at .
mount [ ]*
Attempt to mount the named device at
the directory . This
may be of the form mtd@name to specify a mtd block device by name.
setkey
- currenlty undefined -
setprop
Set system property
to .
setrlimit
Set the rlimit for a resource.
start
Start a service running if it is not
already running.
stop
Stop a service from running if it is
currently running.
symlink
Create a symbolic link at
with the value .
write [ ]*
Open the file at
and write one or more strings to it with write(2).
属性(Properties)初始化程序(Init)可以根据需要修改一些系统的属性。
属性
说明
init.action
Equal to the name of the action
currently being executed or "" if none.
init.command
Equal to the command being executed or
"" if none.
init.svc.
State of a named service ("stopped",
"running", or "restarting").
init.rc文件示例on boot
export PATH /sbin:/system/sbin:/system/bin
export LD_LIBRARY_PATH /system/lib
mkdir /dev
mkdir /proc
mkdir /sys
mount tmpfs tmpfs /dev
mkdir /dev/pts
mkdir /dev/socket
mount devpts devpts /dev/pts
mount proc proc /proc
mount sysfs sysfs /sys
write /proc/cpu/alignment 4
ifup lo
hostname localhost
domainname localhost
mount yaffs2 mtd@system /system
mount yaffs2 mtd@userdata /data
import /system/etc/init.conf
class_start default
service adbd /sbin/adbd
user adb
group adb
service usbd /system/bin/usbd -r
user usbd
group usbd
socket usbd 666
service zygote /system/bin/app_process -Xzygote /system/bin --zygote
socket zygote 666
service runtime /system/bin/runtime
user system
group system
on device-added-/dev/compass
start akmd
on device-removed-/dev/compass
stop akmd
service akmd /sbin/akmd
disabled
user akmd
group akmd
)
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