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