init.rc 語法與解析

版權說明：本文爲 開開向前衝 原創文章，轉載請註明出處；
注：限於作者水平有限，文中有不對的地方還請指教。

本文基於Android 6.0，涉及源碼如下：

/system/core/rootdir/init.rc
/system/core/init/init_parser.cpp

一：init.rc 語法

一個完整的init.rc 腳本由4中類型聲明組成。即：
Action（動作）
Commands（命令）
Services（服務）
Options（選項）

Action 和Services 表明一個新語句的開始，這兩個關鍵字後面跟着的Commands 或者 Options 都是屬於這個語句；
Action 和Services 都有唯一的名字，如果出現動作或者服務重名，則會被當做錯誤處理。

1：Action（動作）

語法格式

on <trigger>   ##觸發條件
     <command1>  ##執行命令
     <command2>  ##可以同時執行多個命令
     <command3>

其中trigger 是觸發條件，即當觸發條件滿足時將 依次 執行commands

舉例說明：下面這句話的意思是當屬性值滿足persist.service.adb.enable=1時，啓動adbd 進程；
on property:persist.service.adb.enable=1
   start adbd

具體實現：當系統變化的時候，系統會對init.rc 中的每個<trigger>進行匹配，只要發現符合條件的Action，就會把它加入 “命令執行隊列”的尾部（除非這個Action 在隊列中已經存在）， 然後系統在對這些Commands按順序執行；

2：Commands（命令）

命令將在觸發條件發生時被一個個執行。

init.rc中常見的trigger如下：

trigger	Description
boot	init程序啓動後觸發的第一個事件
<name>=<value>	當屬性<name> 滿足<value>時觸發
device-added/removed-<patch>	當設備節點添加/刪除時觸發此事件
sevice-exited-<name>	當指定服務<name> 存在時觸發

init.rc中常見的Commands如下：

Command	Description
exec <path> [<argument>]*	Fork 並執行一個程序，其路徑爲<path>。該命令將阻塞 直到該程序啓動完成
export <name> <value>	設置某個環境變量<name> 的值爲<value>。對全局有效，之後的進程都將繼承這個變量
ifup <interface>	使網絡接口<interface> 成功連接
import <filename>	解析另一個配置文件<filename>，以擴展當前配置
chdir <directory>	更換工作目錄爲<directory>
chmod <octal-mode> <path>	更改文件訪問權限
chown <owner> <group> <path>	更改文件所有者和羣組
mount <type> <device> <dir> [<mountoption>]*	嘗試在指定路徑上掛載一個設備
start <service>	啓動一個服務，如果它沒有處於運行狀態的話
stop <service>	停止一個服務，如果它當前處於運行狀態的話
setprop <name> <value>	設置系統屬性<name> 的值爲 <value>
trigger <event>	觸發一個事件

很多沒有列舉完成，但是很多Commands 可以根據名字理解意思，如下舉幾個例子，例子都是init.rc中的內容；

on init
      symlink /sys/kernel/debug /d
      mount cgroup none /acct cpuacct
      mkdir /acct/uid
      chown root system /sys/fs/cgroup/memory/sw/tasks
      chmod 0660 /sys/fs/cgroup/memory/sw/tasks

on property:sys.boot_from_charger_mode=1
class_stop charger
trigger late-init

3：Services（服務）

3.1：命令格式：

service <name> <pathname> [ <argument> ]*
        <option>
        <option>
        ...

• <name>——表示service 的名字；
• <pathname>——表示service所在路徑，此處的service是可執行文件，所以一定有存儲路徑；
• <argument>——啓動service所帶的參數；
• <option>——對此service的約束選項，後面將詳細講解；

Service 樣例如下：

service servicemanager /system/bin/servicemanager
    class core
    user system
    group system
    critical
    onrestart restart healthd
    onrestart restart zygote
    onrestart restart media
    onrestart restart surfaceflinger
    onrestart restart drm

4：Options（選項）

init.rc 中可用的選項如下：

Option	Description
critical	表明這是對設備至關重要的服務；如果它在四分鐘內退出超過四次，則設備將進入Recovery 模式
disabled	表示此服務是不會自動啓動，而是需要通過顯示調用服務名來啓動
setenv <name> <value>	設置環境變量<name> 爲值<value>
socket <name> <type> <perm> [<user> [<group>] ]	創建一個名爲dev/socket/<name>的 socket，然後將它的fd值傳給啓動它的進，有效的<type>值包括dgram,stream 和seqpacket。ueser 和group 的默認值爲0。
user <username>	在啓動服務前將用戶切換至<username>,默認情況下用戶都是root。
group <groupname> [<groupname>]*	在啓動服務前將用戶組切換至<groupname>
oneshot	當次服務退出時，不要主動去重啓它
class <name>	爲該服務指定一個class 名。同一個class 的所有服務必須同時啓動或者停止。默認情況下服務的class名是“default”
onrestart	當次服務重啓時，執行某些命令

---

二：init.rc解析

/system/core/init/init.cpp
/system/core/init/init_parser.cpp

1：init.rc腳本基本結構

init.rc 腳本的基本單位爲section，即片段，section 分爲三類，分別由三個關鍵字(所謂關鍵字即每一行的第一列)來區分，這三個關鍵字是on、service、import。

• on ——即前文的action 的起始關鍵字；
  on 類型的section 表示一系列命令的組合；

 on init
    loglevel 3
    symlink /system/etc /etc
    symlink /sys/kernel/debug /d
    symlink /system/vendor /vendor
    mount cgroup none /acct cpuacct
    mkdir /acct/uid

這條命令包含上述的命令，命令的執行事以section 爲單位執行的，所以這幾條命令是一起執行的，而不會單獨執行，那它們是在那裏執行呢？——這是由init.cpp中的main()方法決定的，init.cpp在某個階段會執行

action_for_each_trigger("init", action_add_queue_tail);

該方法就是將 on init 開始的section 裏面的所有命令加入到一個執行隊列，在未來的某個時間會順序的執行，所以調用action_for_each_trigger的先後決定了命令執行的先後順序；

• service ——即前文所說的服務起始關鍵字；
  service類型的section代表了一個可執行程序；

service servicemanager /system/bin/servicemanager
    class core
    user system
    group system
    critical
    onrestart restart healthd
    onrestart restart zygote
    onrestart restart media
    onrestart restart surfaceflinger
    onrestart restart drm

服務的內容之前已經介紹過，可以看看前文，那service 類型的section標識的服務在什麼時候調用呢？—— 是在class_start命令被執行的時候，class_start命令總是存在於on 類型的section中；

class_start core #這樣一條命令代表將啓動所有類型爲core的service
所以可以看出android的啓動過程主要就是on類型的section被執行的過程。

• import —— import類型的section代表將引入另外一個.rc文件；

import /init.environ.rc
import /init.usb.rc

相當包含另外一些section, 在解析完init.rc文件後繼續會調用init_parse_config_file來解析引入的.rc文件

2：解析過程

init.rc是一個純文本文件，我們需要程序去解析init.rc，然後交給程序運行，解析init.rc的過程就是識別一個個section的過程，將各個section的信息保存下來，然後在init.c的main()中去執行一個個命令。

android採用雙向鏈表來存儲section的信息，解析完成之後，會得到三個雙向鏈表action_list、service_list、import_list來分別存儲三種section的信息上。

/system/core/init/init_parser.cpp
static list_declare(service_list);
static list_declare(action_list);
static list_declare(action_queue);

1:init.c中調用init_parse_config_file("/init.rc")

int init_parse_config_file(const char *fn)
{
    char *data;
    data = read_file(fn, 0);//讀文件數據
    if (!data) return -1;
<span class="token function">parse_config</span><span class="token punctuation">(</span>fn<span class="token punctuation">,</span> <span class="token keyword">data</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token comment">//解析數據</span>
<span class="token function">DUMP</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">return</span> <span class="token number">0</span><span class="token punctuation">;</span>

}

2:parse_config

static void parse_config(const char *fn, const std::string& data)
{
    struct listnode import_list;
    struct listnode *node;
    char *args[INIT_PARSER_MAXARGS];
<span class="token keyword">int</span> nargs <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span>

parse_state state<span class="token punctuation">;</span>
state<span class="token punctuation">.</span>filename <span class="token operator">=</span> fn<span class="token punctuation">;</span>
state<span class="token punctuation">.</span>line <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span>
state<span class="token punctuation">.</span>ptr <span class="token operator">=</span> <span class="token function">strdup</span><span class="token punctuation">(</span>data<span class="token punctuation">.</span><span class="token function">c_str</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>  <span class="token comment">// TODO: fix this code!</span>
state<span class="token punctuation">.</span>nexttoken <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span>
state<span class="token punctuation">.</span>parse_line <span class="token operator">=</span> parse_line_no_op<span class="token punctuation">;</span>

<span class="token function">list_init</span><span class="token punctuation">(</span><span class="token operator">&amp;</span>import_list<span class="token punctuation">)</span><span class="token punctuation">;</span>
state<span class="token punctuation">.</span>priv <span class="token operator">=</span> <span class="token operator">&amp;</span>import_list<span class="token punctuation">;</span>

<span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token punctuation">;</span><span class="token punctuation">;</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token keyword">switch</span> <span class="token punctuation">(</span><span class="token function">next_token</span><span class="token punctuation">(</span><span class="token operator">&amp;</span>state<span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token comment">//next_token()根據從state.ptr開始遍歷</span>
    <span class="token keyword">case</span> T_EOF<span class="token operator">:</span> <span class="token comment">//遍歷到文件結尾，然後goto解析import的.rc文件</span>
        state<span class="token punctuation">.</span><span class="token function">parse_line</span><span class="token punctuation">(</span><span class="token operator">&amp;</span>state<span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
        <span class="token keyword">goto</span> parser_done<span class="token punctuation">;</span>
    <span class="token keyword">case</span> T_NEWLINE<span class="token operator">:</span> <span class="token comment">//到了一行結束</span>
        state<span class="token punctuation">.</span>line<span class="token operator">++</span><span class="token punctuation">;</span>
        <span class="token keyword">if</span> <span class="token punctuation">(</span>nargs<span class="token punctuation">)</span> <span class="token punctuation">{</span>
            <span class="token keyword">int</span> kw <span class="token operator">=</span> <span class="token function">lookup_keyword</span><span class="token punctuation">(</span>args<span class="token punctuation">[</span><span class="token number">0</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 找到這一行的關鍵字</span>
            <span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token function">kw_is</span><span class="token punctuation">(</span>kw<span class="token punctuation">,</span> SECTION<span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token comment">// 如果這是一個section的第一行</span>
                state<span class="token punctuation">.</span><span class="token function">parse_line</span><span class="token punctuation">(</span><span class="token operator">&amp;</span>state<span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
                <span class="token function">parse_new_section</span><span class="token punctuation">(</span><span class="token operator">&amp;</span>state<span class="token punctuation">,</span> kw<span class="token punctuation">,</span> nargs<span class="token punctuation">,</span> args<span class="token punctuation">)</span><span class="token punctuation">;</span>
            <span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token punctuation">{</span> <span class="token comment">//如果這不是一個section的第一行</span>
                state<span class="token punctuation">.</span><span class="token function">parse_line</span><span class="token punctuation">(</span><span class="token operator">&amp;</span>state<span class="token punctuation">,</span> nargs<span class="token punctuation">,</span> args<span class="token punctuation">)</span><span class="token punctuation">;</span>
            <span class="token punctuation">}</span>
            nargs <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span>
        <span class="token punctuation">}</span>
        <span class="token keyword">break</span><span class="token punctuation">;</span>
    <span class="token keyword">case</span> T_TEXT<span class="token operator">:</span> <span class="token comment">// 遇到普通字符</span>
        <span class="token keyword">if</span> <span class="token punctuation">(</span>nargs <span class="token operator">&lt;</span> INIT_PARSER_MAXARGS<span class="token punctuation">)</span> <span class="token punctuation">{</span>
            args<span class="token punctuation">[</span>nargs<span class="token operator">++</span><span class="token punctuation">]</span> <span class="token operator">=</span> state<span class="token punctuation">.</span>text<span class="token punctuation">;</span>
        <span class="token punctuation">}</span>
        <span class="token keyword">break</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span>

parser_done:
list_for_each(node, &import_list) {
struct import *import = node_to_item(node, struct import, list);
int ret;

     ret <span class="token operator">=</span> <span class="token function">init_parse_config_file</span><span class="token punctuation">(</span>import<span class="token operator">-&gt;</span>filename<span class="token punctuation">)</span><span class="token punctuation">;</span>
     <span class="token keyword">if</span> <span class="token punctuation">(</span>ret<span class="token punctuation">)</span>
         <span class="token function">ERROR</span><span class="token punctuation">(</span><span class="token string">"could not import file '%s' from '%s'\n"</span><span class="token punctuation">,</span>
               import<span class="token operator">-&gt;</span>filename<span class="token punctuation">,</span> fn<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>

}

next_token() 解析完init.rc中一行之後，會返回T_NEWLINE，這時調用lookup_keyword函數來找出這一行的關鍵字, lookup_keyword返回的是一個整型值，對應keyword_info[]數組的下標，keyword_info[]存放的是keyword_info結構體類型的數據，

struct {
   const char *name;                                    //關鍵字的名稱
   int (*func)(int nargs, char **args);            //對應的處理函數
   unsigned char nargs;                                //參數個數
   unsigned char flags;                                 //flag標識關鍵字的類型,包括COMMAND、OPTION、SECTION
} keyword_info

keyword_info[]中存放的是所有關鍵字信息，每一項對應一個關鍵字；
根據每一項的flags就可以判斷出關鍵字的類型，如新的一行是SECTION，就調用parse_new_section()來解析這一行, 如新的一行不是一個SECTION的第一行，那麼調用state.parseline()來解析(state.parseline所對應的函數會根據section類型的不同而不同)，在parse_new_section()中進行動態設置。

static void parse_new_section(struct parse_state *state, int kw,
                       int nargs, char **args)
{
    printf("[ %s %s ]\n", args[0],
           nargs > 1 ? args[1] : "");
    switch(kw) {
    case K_service: //解析service
        state->context = parse_service(state, nargs, args);
        if (state->context) {
            state->parse_line = parse_line_service; //Service 對應的parse_line
            return;
        }
        break;
    case K_on://解析 on 開頭的action
        state->context = parse_action(state, nargs, args);
        if (state->context) {
            state->parse_line = parse_line_action; //action 對應的parse_line
            return;
        }
        break;
    case K_import: //解析import
        parse_import(state, nargs, args);
        break;
    }
    state->parse_line = parse_line_no_op;
}

三種類型的section: service、on、import, service對應的state.parse_line爲parse_line_service,
on對應的state.parse_line爲parse_line_action, import section中只有一行所以沒有對應的state.parseline。

鑑於篇幅原因，使用文字描述parse_service過程，parse_action，parse_import解析也是類似的：

parse_service會去service_list鏈表查找有沒有該命名的service(svc = service_find_by_name(args[1]);)，如果沒有則會構造service 對象並添加到service_list鏈表中，返回該service 對象；但是這個service 沒有Options，然後通過parse_line_service 解析Options選項填充service 對象；

3：相關結構體

一個on類型的section對應一個action， action類型定義如下：

struct action {
        /* node in list of all actions */
    struct listnode alist;
        /* node in the queue of pending actions */
    struct listnode qlist;
        /* node in list of actions for a trigger */
    struct listnode tlist;
<span class="token keyword">unsigned</span> hash<span class="token punctuation">;</span>

    <span class="token comment">/* list of actions which triggers the commands*/</span>
<span class="token keyword">struct</span> <span class="token class-name">listnode</span> triggers<span class="token punctuation">;</span>
<span class="token keyword">struct</span> <span class="token class-name">listnode</span> commands<span class="token punctuation">;</span> <span class="token comment">//command的雙向鏈表</span>
<span class="token keyword">struct</span> <span class="token class-name">command</span> <span class="token operator">*</span>current<span class="token punctuation">;</span>

};

每個on類型section的第二行開始每一行都解析了一個command, 所有command組成一個雙向鏈表指向該action的commands字段中。

command結構體定義如下：

struct command
{
        /* list of commands in an action */
    struct listnode clist;
<span class="token keyword">int</span> <span class="token punctuation">(</span><span class="token operator">*</span>func<span class="token punctuation">)</span><span class="token punctuation">(</span><span class="token keyword">int</span> nargs<span class="token punctuation">,</span> <span class="token keyword">char</span> <span class="token operator">*</span><span class="token operator">*</span>args<span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token keyword">int</span> line<span class="token punctuation">;</span>
<span class="token keyword">const</span> <span class="token keyword">char</span> <span class="token operator">*</span>filename<span class="token punctuation">;</span>

<span class="token keyword">int</span> nargs<span class="token punctuation">;</span>
<span class="token keyword">char</span> <span class="token operator">*</span>args<span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">;</span>

};

command結構體比較簡單, 用於標識一個命令，包含雙向鏈表指針、對應的執行函數、參數個數以及命令關鍵字。

service結構體定義如下：

struct service {
    void NotifyStateChange(const char* new_state);
    <span class="token comment">/* list of all services */</span>
<span class="token keyword">struct</span> <span class="token class-name">listnode</span> slist<span class="token punctuation">;</span>

<span class="token keyword">char</span> <span class="token operator">*</span>name<span class="token punctuation">;</span>
<span class="token keyword">const</span> <span class="token keyword">char</span> <span class="token operator">*</span>classname<span class="token punctuation">;</span>

<span class="token keyword">unsigned</span> flags<span class="token punctuation">;</span>
pid_t pid<span class="token punctuation">;</span>
time_t time_started<span class="token punctuation">;</span>    <span class="token comment">/* time of last start */</span>
time_t time_crashed<span class="token punctuation">;</span>    <span class="token comment">/* first crash within inspection window */</span>
<span class="token keyword">int</span> nr_crashed<span class="token punctuation">;</span>         <span class="token comment">/* number of times crashed within window */</span>

uid_t uid<span class="token punctuation">;</span>
gid_t gid<span class="token punctuation">;</span>
gid_t supp_gids<span class="token punctuation">[</span>NR_SVC_SUPP_GIDS<span class="token punctuation">]</span><span class="token punctuation">;</span>
size_t nr_supp_gids<span class="token punctuation">;</span>

<span class="token keyword">const</span> <span class="token keyword">char</span><span class="token operator">*</span> seclabel<span class="token punctuation">;</span>

<span class="token keyword">struct</span> <span class="token class-name">socketinfo</span> <span class="token operator">*</span>sockets<span class="token punctuation">;</span>
<span class="token keyword">struct</span> <span class="token class-name">svcenvinfo</span> <span class="token operator">*</span>envvars<span class="token punctuation">;</span>

<span class="token keyword">struct</span> <span class="token class-name">action</span> onrestart<span class="token punctuation">;</span>  <span class="token comment">/* Actions to execute on restart. */</span>

std<span class="token operator">::</span>vector<span class="token operator">&lt;</span>std<span class="token operator">::</span>string<span class="token operator">&gt;</span><span class="token operator">*</span> writepid_files_<span class="token punctuation">;</span>

<span class="token comment">/* keycodes for triggering this service via /dev/keychord */</span>
<span class="token keyword">int</span> <span class="token operator">*</span>keycodes<span class="token punctuation">;</span>
<span class="token keyword">int</span> nkeycodes<span class="token punctuation">;</span>
<span class="token keyword">int</span> keychord_id<span class="token punctuation">;</span>

IoSchedClass ioprio_class<span class="token punctuation">;</span>
<span class="token keyword">int</span> ioprio_pri<span class="token punctuation">;</span>

<span class="token keyword">int</span> nargs<span class="token punctuation">;</span>
<span class="token comment">/* "MUST BE AT THE END OF THE STRUCT" */</span>
<span class="token keyword">char</span> <span class="token operator">*</span>args<span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">;</span>

};

service結構體存儲了service的相關信息, 包括進程號、啓動時間、名字等， onrestart這個option後面通常跟着一個命令，所以也用action結構體來表示。
例如：

service servicemanager /system/bin/servicemanager
    class core
    user system
    group system
    critical
    onrestart restart healthd
    onrestart restart zygote
    onrestart restart media
    onrestart restart surfaceflinger
    onrestart restart drm

init.rc中配置的service 啓動流程：

/system/core/rootdir/init.rc
      class_start core
  on nonencrypted
      class_start main
      class_start late_start

/system/core/init/keywords.h
KEYWORD(class_start, COMMAND, 1, do_class_start)

/system/core/init/builtins.c
int do_class_start(int nargs, char args)
{
/* Starting a class does not start services
* which are explicitly disabled. They must
* be started individually.
*/
service_for_each_class(args[1], service_start_if_not_disabled);
return 0;
}

/system/core/init/init_parser.cpp
void service_for_each_class(const char classname,
void (func)(struct service svc))
{
struct listnode node;
struct service *svc;
list_for_each(node, &service_list) {
svc = node_to_item(node, struct service, slist);
if (!strcmp(svc->classname, classname)) {
func(svc);
}
}
}

/system/core/init/builtins.cpp
static void service_start_if_not_disabled(struct service *svc)
{
if (!(svc->flags & SVC_DISABLED)) {
service_start(svc, NULL);
} else {
svc->flags |= SVC_DISABLED_START;
}
}

/system/core/init/init.c
void service_start(struct service svc, const char dynamic_args)
{
struct stat s;
pid_t pid;
int needs_console;
int n;
char *scon = NULL;
int rc;

    <span class="token comment">/* starting a service removes it from the disabled or reset
     * state and immediately takes it out of the restarting
     * state if it was in there
     */</span>
  <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
  pid <span class="token operator">=</span> <span class="token function">fork</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token comment">//fork 子進程</span>
  <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
  <span class="token keyword">for</span> <span class="token punctuation">(</span>si <span class="token operator">=</span> svc<span class="token operator">-&gt;</span>sockets<span class="token punctuation">;</span> si<span class="token punctuation">;</span> si <span class="token operator">=</span> si<span class="token operator">-&gt;</span>next<span class="token punctuation">)</span> <span class="token punctuation">{</span>
        <span class="token keyword">int</span> socket_type <span class="token operator">=</span> <span class="token punctuation">(</span>
                <span class="token operator">!</span><span class="token function">strcmp</span><span class="token punctuation">(</span>si<span class="token operator">-&gt;</span>type<span class="token punctuation">,</span> <span class="token string">"stream"</span><span class="token punctuation">)</span> <span class="token punctuation">?</span> SOCK_STREAM <span class="token punctuation">:</span>
                    <span class="token punctuation">(</span><span class="token operator">!</span><span class="token function">strcmp</span><span class="token punctuation">(</span>si<span class="token operator">-&gt;</span>type<span class="token punctuation">,</span> <span class="token string">"dgram"</span><span class="token punctuation">)</span> <span class="token punctuation">?</span> SOCK_DGRAM <span class="token punctuation">:</span> SOCK_SEQPACKET<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token comment">//判斷socket 類型</span>
        <span class="token keyword">int</span> s <span class="token operator">=</span> <span class="token function">create_socket</span><span class="token punctuation">(</span>si<span class="token operator">-&gt;</span>name<span class="token punctuation">,</span> socket_type<span class="token punctuation">,</span>
                              si<span class="token operator">-&gt;</span>perm<span class="token punctuation">,</span> si<span class="token operator">-&gt;</span>uid<span class="token punctuation">,</span> si<span class="token operator">-&gt;</span>gid<span class="token punctuation">,</span> si<span class="token operator">-&gt;</span>socketcon <span class="token punctuation">?</span><span class="token punctuation">:</span> scon<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token comment">//創建socket對應的fd</span>
        <span class="token keyword">if</span> <span class="token punctuation">(</span>s <span class="token operator">&gt;=</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
            <span class="token function">publish_socket</span><span class="token punctuation">(</span>si<span class="token operator">-&gt;</span>name<span class="token punctuation">,</span> s<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token comment">//發佈socket的fd，即將create_socket返回的fd添加到</span>
                                        <span class="token comment">//以"ANDROID_SOCKET_"爲前綴的環境變量；</span>
                                        <span class="token comment">//Zygote的socket的key 爲ANDROID_SOCKET_zygote，也是在這創建的；</span>
        <span class="token punctuation">}</span>
   <span class="token punctuation">}</span>
  <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>