Nginx的主流程的实现函数在./src/core/nginx.c文件中

其中的重点模块会在后面的文章里详解

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大部分初始化工作的中心，变量cycle解析：

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static ngx_uint_t   ngx_show_help;		//是否显示帮助信息
static ngx_uint_t   ngx_show_version;   //是否显示版本号
static ngx_uint_t   ngx_show_configure; //是否显示配置信息
static u_char      *ngx_prefix;			//Nginx的工作目录
static u_char      *ngx_conf_file;		//全局配置文件目录地址
static u_char      *ngx_conf_params;	//配置参数
static char        *ngx_signal;			//信号


static char **ngx_os_environ;


int ngx_cdecl
main(int argc, char *const *argv)
{
    ngx_int_t         i;
    ngx_log_t        *log;
    ngx_cycle_t      *cycle, init_cycle;
    ngx_core_conf_t  *ccf;

    ngx_debug_init();

    if (ngx_strerror_init() != NGX_OK) //警告输出初始化 
	{
        return 1;
    }

    if (ngx_get_options(argc, argv) != NGX_OK) //解析命令行中的参数
	{
        return 1;
    }

    if (ngx_show_version) {
        ngx_write_stderr("nginx version: " NGINX_VER NGX_LINEFEED);

        if (ngx_show_help) {
            ngx_write_stderr(
                "Usage: nginx [-?hvVtq] [-s signal] [-c filename] "
                             "[-p prefix] [-g directives]" NGX_LINEFEED
                             NGX_LINEFEED
                "Options:" NGX_LINEFEED
                "  -?,-h         : this help" NGX_LINEFEED
                "  -v            : show version and exit" NGX_LINEFEED
                "  -V            : show version and configure options then exit"
                                   NGX_LINEFEED
                "  -t            : test configuration and exit" NGX_LINEFEED
                "  -q            : suppress non-error messages "
                                   "during configuration testing" NGX_LINEFEED
                "  -s signal     : send signal to a master process: "
                                   "stop, quit, reopen, reload" NGX_LINEFEED
#ifdef NGX_PREFIX
                "  -p prefix     : set prefix path (default: "
                                   NGX_PREFIX ")" NGX_LINEFEED
#else
                "  -p prefix     : set prefix path (default: NONE)" NGX_LINEFEED
#endif
                "  -c filename   : set configuration file (default: "
                                   NGX_CONF_PATH ")" NGX_LINEFEED
                "  -g directives : set global directives out of configuration "
                                   "file" NGX_LINEFEED NGX_LINEFEED
                );
        }

        if (ngx_show_configure) {
            ngx_write_stderr(
#ifdef NGX_COMPILER
                "built by " NGX_COMPILER NGX_LINEFEED
#endif
#if (NGX_SSL)
#ifdef SSL_CTRL_SET_TLSEXT_HOSTNAME
                "TLS SNI support enabled" NGX_LINEFEED
#else
                "TLS SNI support disabled" NGX_LINEFEED
#endif
#endif
                "configure arguments:" NGX_CONFIGURE NGX_LINEFEED);
        }

        if (!ngx_test_config) {
            return 0;
        }
    }

    /* TODO */ ngx_max_sockets = -1;

    ngx_time_init(); //时间更新并初始化

#if (NGX_PCRE)
    ngx_regex_init();
#endif

    ngx_pid = ngx_getpid(); //获取当前进程pid 并将pid存放在/usr/local/nginx-1.4.7/nginx.pid中

    log = ngx_log_init(ngx_prefix);  //初始化日志，log为日志文件句柄ngx_log_file.fd
    if (log == NULL) {
        return 1;
    }

    /* STUB */
#if (NGX_OPENSSL)
    ngx_ssl_init(log);
#endif

    /*
     * init_cycle->log is required for signal handlers and
     * ngx_process_options()
     */

    ngx_memzero(&init_cycle, sizeof(ngx_cycle_t));//初始化init_cycle
    init_cycle.log = log;
    ngx_cycle = &init_cycle; //将init_cycle赋值给全局变量

    init_cycle.pool = ngx_create_pool(1024, log); //为init_cycle分配1024大小的内存
    if (init_cycle.pool == NULL) {
        return 1;
    }

    if (ngx_save_argv(&init_cycle, argc, argv) != NGX_OK) //保存Nginx命令行中的参数和变量,到全局变量ngx_argv 
	{
        return 1;
    }

    if (ngx_process_options(&init_cycle) != NGX_OK) //将ngx_get_options中获得的参数(prefix, conf_prefix, conf_file, conf_param等字段)取值赋值到ngx_cycle中。
	{
        return 1;
    }

    if (ngx_os_init(log) != NGX_OK) //初始化系统相关变量，如内存页面大小ngx_pagesize,ngx_cacheline_size,最大连接数ngx_max_sockets等 
	{
        return 1;
    }

    /*
     * ngx_crc32_table_init() requires ngx_cacheline_size set in ngx_os_init()
     */

    if (ngx_crc32_table_init() != NGX_OK) //初始化一致性hash表，主要作用是用状态机方式加快查询，
	{
        return 1;
    }

    if (ngx_add_inherited_sockets(&init_cycle) != NGX_OK) //ngx_add_inherited_sockets主要是继承了socket的套接字。主要作用是热启动的时候需要平滑过渡
	{
        return 1;
    }
 	//前置的初始化模块，对模块进行编号处理
    ngx_max_module = 0;
    for (i = 0; ngx_modules[i]; i++) {
        ngx_modules[i]->index = ngx_max_module++;
    }

    cycle = ngx_init_cycle(&init_cycle); //完成变量cycle的初始化
    if (cycle == NULL) {
        if (ngx_test_config) {
            ngx_log_stderr(0, "configuration file %s test failed",
                           init_cycle.conf_file.data);
        }

        return 1;
    }

    if (ngx_test_config) {
        if (!ngx_quiet_mode) {
            ngx_log_stderr(0, "configuration file %s test is successful",
                           cycle->conf_file.data);
        }

        return 0;
    }

    if (ngx_signal) //如果有信号，则进入ngx_signal_process方法 -s 等实现
	{
        return ngx_signal_process(cycle, ngx_signal); 
    }

    ngx_os_status(cycle->log); //在日志中打印系统状态

    ngx_cycle = cycle;

    ccf = (ngx_core_conf_t *) ngx_get_conf(cycle->conf_ctx, ngx_core_module);//获取配置到指针ccf

    if (ccf->master && ngx_process == NGX_PROCESS_SINGLE) {
        ngx_process = NGX_PROCESS_MASTER;
    }

#if !(NGX_WIN32)

    if (ngx_init_signals(cycle->log) != NGX_OK) {
        return 1;
    }

    if (!ngx_inherited && ccf->daemon) {
        if (ngx_daemon(cycle->log) != NGX_OK) {
            return 1;
        }

        ngx_daemonized = 1;
    }

    if (ngx_inherited) {
        ngx_daemonized = 1;
    }

#endif

    if (ngx_create_pidfile(&ccf->pid, cycle->log) != NGX_OK) //创建pid文件 
	{
        return 1;
    }

    if (cycle->log->file->fd != ngx_stderr) {

        if (ngx_set_stderr(cycle->log->file->fd) == NGX_FILE_ERROR) {
            ngx_log_error(NGX_LOG_EMERG, cycle->log, ngx_errno,
                          ngx_set_stderr_n " failed");
            return 1;
        }
    }

    if (log->file->fd != ngx_stderr) {
        if (ngx_close_file(log->file->fd) == NGX_FILE_ERROR) {
            ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
                          ngx_close_file_n " built-in log failed");
        }
    }

    ngx_use_stderr = 0;

    if (ngx_process == NGX_PROCESS_SINGLE) {
        ngx_single_process_cycle(cycle); //创建worker进程，开始监听

    } else {
        ngx_master_process_cycle(cycle);
    }

    return 0;
}