tinyhttpd是一轻量级的web 服务器,最近几天终于抽出时间来研究研究了。其源码百度即可下载,500多行,确实是学习linux编程的好材料。很多网友都写了关于tinyhttpd的博文,但是我还是觉得不够深入,严格说是写得不够深入,往往就是把500多行代码一扔,分析下主要过程,画个流程图就完事了。我怎么觉得还有很多东西可以挖一挖呢,也许还可再调整一下代码,虽然目前也不清楚可调整多少,待我细细道来。
我分析的过程就按主要路线走,也就是这样一个主干道流程:服务器创建socket并监听某一端口->浏览器输入url发出请求->服务器收到请求,创建线程处理请求,主线程继续等待->新线程读取http请求,并解析相关字段,读取文件内容或者执行CGI程序并返回给浏览器->关闭客户端套接字,新线程退出
咱们先来看看main函数
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- int main(void)
- {
- int server_sock = -1;
- u_short port = 0;
- int client_sock = -1;
- struct sockaddr_in client_name;
- int client_name_len = sizeof(client_name);
- pthread_t newthread;
- server_sock = startup(&port);
- "httpd running on port %d\n", port);
- while (1)
- {
- client_sock = accept(server_sock,
- struct sockaddr *)&client_name,
- &client_name_len);
- if (client_sock == -1)
- "accept");
- if (pthread_create(&newthread , NULL, accept_request, client_sock) != 0)
- "pthread_create");
- }
- close(server_sock);
- return(0);
- }
这段代码,只要是稍微了解linux的网络编程就很好懂,创建服务端socket,绑定、监听、等待客户端连接。只不过作者把这些步骤都放在了一个叫startup的函数里。那来看startup
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- int startup(u_short *port)
- {
- int httpd = 0;
- struct sockaddr_in name;
- httpd = socket(PF_INET, SOCK_STREAM, 0);
- if (httpd == -1)
- "socket");
- sizeof(name));//也可以用bzero
- name.sin_family = AF_INET;
- name.sin_port = htons(*port);
- //任何网络接口
- if (bind(httpd, (struct sockaddr *)&name, sizeof(name)) < 0)
- "bind");
- if (*port == 0) /* if dynamically allocating a port */
- {
- int namelen = sizeof(name);
- if (getsockname(httpd, (struct sockaddr *)&name, &namelen) == -1)
- "getsockname");
- //系统动态分配一个端口号
- }
- if (listen(httpd, 5) < 0)
- "listen");
- return(httpd);//返回服务套接字描述符
- }
很常见的步骤,就不多说了。
此后,服务端就accept等待连接,作者其实没有关心客户端来自哪里,那accept的第二、第三参数完全可以为NULL。接着就创建线程把客户端套接字作为参数传过去了,由新线程处理请求,这是服务器编程的常用手段,提高并发性。注意这里的线程函数并不完全合法,至少在linux上就不符合线程函数的原型定义,编译时编译器也只是警告而未报错。
接下来重点就在线程函数accept_request上了
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- void accept_request(int client)
- {
- char buf[1024];
- int numchars;
- char method[255];
- char url[255];
- char path[512];
- size_t i, j;
- struct stat st;
- int cgi = 0; /* becomes true if server decides this is a CGI
- * program */
- char *query_string = NULL;
- sizeof(buf));
- i = 0; j = 0;
- while (!ISspace(buf[j]) && (i < sizeof(method) - 1))
- {
- method[i] = buf[j];
- i++; j++;
- }
- '\0';
- if (strcasecmp(method, "GET") && strcasecmp(method, "POST"))
- {
- unimplemented(client);
- return;
- }
- if (strcasecmp(method, "POST") == 0)
- cgi = 1;
- i = 0;
- while (ISspace(buf[j]) && (j < sizeof(buf)))
- j++;
- while (!ISspace(buf[j]) && (i < sizeof(url) - 1) && (j < sizeof(buf)))
- {
- url[i] = buf[j];
- i++; j++;
- }
- '\0';
- if (strcasecmp(method, "GET") == 0)
- {
- query_string = url;
- while ((*query_string != '?') && (*query_string != '\0'))
- query_string++;
- if (*query_string == '?')
- {
- cgi = 1;
- '\0';
- query_string++;
- }
- }
- "htdocs%s", url);
- if (path[strlen(path) - 1] == '/')
- "index.html");
- if (stat(path, &st) == -1) {
- while ((numchars > 0) && strcmp("\n", buf)) /* read & discard headers */
- sizeof(buf));
- not_found(client);
- }
- else
- {
- if ((st.st_mode & S_IFMT) == S_IFDIR)
- "/index.html");
- if ((st.st_mode & S_IXUSR) ||
- (st.st_mode & S_IXGRP) ||
- (st.st_mode & S_IXOTH) )
- cgi = 1;
- if (!cgi)
- serve_file(client, path);
- else
- execute_cgi(client, path, method, query_string);
- }
- close(client);
- }
首先很关键一点要理解get_line的意思。我们要知道当在浏览器中输入url后enter之后,它发给服务器是文本型的字符串,遵循http请求格式,类似下面的:
GET / HTTP/1.1
HOST:www.abc.com
Content-type:text/html
...
get_line干的事就是读取一行,并且不管原来是以\n还是\r\n结束,均转化为以\n再加\0字符结束。其实现如下:
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- int get_line(int sock, char *buf, int size)
- {
- int i = 0;
- char c = '\0';
- int n;
- while ((i < size - 1) && (c != '\n'))
- {
- //从sock中一次读一个字符,循环读
- if (n > 0)
- {
- if (c == '\r') //如果读到回车,一般紧接着字符就是\n
- {
- n = recv(sock, &c, 1, MSG_PEEK);
- if ((n > 0) && (c == '\n'))
- //这时再读,c还是\n,循环跳出
- else
- '\n';
- }
- buf[i] = c;
- i++;
- }
- else
- '\n';
- }
- '\0';
- return(i);//返回读取的字符数
- }
get_line完后,就是开始解析第一行,判断是GET方法还是POST方法,目前只支持这两种。如果是POST,还是把cgi置1,表明要运行CGI程序;如果是GET方法且附带以?开头的参数时,也认为是执行CGI程序
还是获取要访问的url,可以是很常见的/,/index.html等等。该程序默认为根目录是在htdocs下的,且默认文件是index.html。另外还判断了给定文件是否有可执权限,如果有,则认为是CGI程序。最后根据变量cgi的值来进行相应选择:读取静态文件或者执行CGI程序返回结果。
我们首先看看最简单的静态文件情况,调用函数serve_file
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- void serve_file(int client, const char *filename)
- {
- FILE *resource = NULL;
- int numchars = 1;
- char buf[1024];
- 'A'; buf[1] = '\0';
- while ((numchars > 0) && strcmp("\n", buf)) /* read & discard headers */
- sizeof(buf));//必须要读完客户端发来的头部,否则后来的send不能正常显示在浏览器中。
- "r");
- if (resource == NULL)
- not_found(client);
- else
- {
- headers(client, filename);
- cat(client, resource);
- }
- fclose(resource);
- }
将文件名作为参数,首先读完客户端的头部,然后打开创建文件流。为了模拟http响应,首先向客户端发送头部,头部信息至少包含以下几点:
http/1.0 200 ok
server:
content-type:
\r\n(一个空白行,标识头部结束)
最后发送数据体部分,即文件内容,在cat方法中,fgets每读入一行,就send,直到末尾。headers和cat函数就不在这里列出了。下面,我们来看看一个具体测试例子,紧接着在gdb中调试
我在根目录下的htdocs下建立一个新文件index2.html,内容如下:
<a href="http://10.108.222.96:54205/test.sh">Display Date</a>
我在这里放了一个链接,href部分是关于cgi的,先不管,就只看文本部分能否显示在浏览器中。
首先编译之后直接运行./httpd,程序打印"httpd running on port 53079"
我们在浏览器中访问index2.html文件,如下图所示:
文本能正确显示了。那如何在gdb中调试观察呢?
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- xiaoqiang@ljq-Lenovo:~/chenshi/tinyhttpd-0.1.0$ gdb attach 7029 【通过ps查看httpd进程的PID,然后gdb attach之】
- Attaching to process 7029
- Reading symbols from /home/xiaoqiang/chenshi/tinyhttpd-0.1.0/httpd...done.
- Reading symbols from /lib/i386-linux-gnu/libpthread.so.0...(no debugging symbols found)...done.
- [Thread debugging using libthread_db enabled]
- Using host libthread_db library "/lib/i386-linux-gnu/libthread_db.so.1".
- Loaded symbols for /lib/i386-linux-gnu/libpthread.so.0
- Reading symbols from /lib/i386-linux-gnu/libc.so.6...(no debugging symbols found)...done.
- Loaded symbols for /lib/i386-linux-gnu/libc.so.6
- Reading symbols from /lib/ld-linux.so.2...(no debugging symbols found)...done.
- Loaded symbols for /lib/ld-linux.so.2
- 0xb7750424 in __kernel_vsyscall ()
- (gdb) bt
- #0 0xb7750424 in __kernel_vsyscall ()
- #1 0xb772dc08 in accept () from /lib/i386-linux-gnu/libpthread.so.0
- #2 0x0804a8d6 in main () at httpd.c:516
- (gdb) l accept_request
- warning: Source file is more recent than executable.
- 47 /* A request has caused a call to accept() on the server port to
- 48 * return. Process the request appropriately.
- 49 * Parameters: the socket connected to the client */
- 50 /**********************************************************************/
- 51 void accept_request(int client)
- 52 {
- 53 char buf[1024];
- 54 int numchars;
- 55 char method[255];
- 56 char url[255];
- (gdb) l
- 57 char path[512];
- 58 size_t i, j;
- 59 struct stat st;
- 60 int cgi = 0; /* becomes true if server decides this is a CGI
- 61 * program */
- 62 char *query_string = NULL;
- 63
- 64 numchars = get_line(client, buf, sizeof(buf));//从套接字中读取一行
- 65 i = 0; j = 0;
- 66 while (!ISspace(buf[j]) && (i < sizeof(method) - 1))
- (gdb) b 64 【在64行设置断点,观察读到的是什么】
- Breakpoint 1 at 0x8048b3f: file httpd.c, line 64.
- (gdb) c
- Continuing. 【直到在浏览器中发起了请求,后面的才会打印出来】
- [New Thread 0xb63feb40 (LWP 7655)]
- [Switching to Thread 0xb63feb40 (LWP 7655)]
- Breakpoint 1, accept_request (client=4) at httpd.c:64
- 64 numchars = get_line(client, buf, sizeof(buf));//从套接字中读取一行
- (gdb) n
- 65 i = 0; j = 0;
- (gdb) p buf 【打印读到的一行】
- $1 = "GET /index2.html HTTP/1.1\n", '\000' <repeats 997 times> 【果真是HTTP GET请求的第一行】
- (gdb) l
- 60 int cgi = 0; /* becomes true if server decides this is a CGI
- 61 * program */
- 62 char *query_string = NULL;
- 63
- 64 numchars = get_line(client, buf, sizeof(buf));//从套接字中读取一行
- 65 i = 0; j = 0;
- 66 while (!ISspace(buf[j]) && (i < sizeof(method) - 1))
- 67 {
- 68 method[i] = buf[j];
- 69 i++; j++;
- (gdb) l
- 70 }
- 71 method[i] = '\0';//获取到了HTTP方法
- 72
- 73 if (strcasecmp(method, "GET") && strcasecmp(method, "POST"))
- 74 {
- 75 //忽略大小写比较
- 76 unimplemented(client);
- 77 return;//尚未支持的请求方法,线程返回
- 78 }
- 79
- (gdb) l serve_file 【其它的细节调试就不在这里演示了,直接跳到serve_file里】
- 412 * Parameters: a pointer to a file structure produced from the socket
- 413 * file descriptor
- 414 * the name of the file to serve */
- 415 /**********************************************************************/
- 416 void serve_file(int client, const char *filename)
- 417 {
- 418 FILE *resource = NULL;
- 419 int numchars = 1;
- 420 char buf[1024];
- 421
- (gdb) l
- 422 buf[0] = 'A'; buf[1] = '\0';
- 423 while ((numchars > 0) && strcmp("\n", buf)) /* read & discard headers */
- 424 numchars = get_line(client, buf, sizeof(buf));
- 425
- 426 resource = fopen(filename, "r");
- 427 if (resource == NULL)
- 428 not_found(client);
- 429 else
- 430 {
- 431 headers(client, filename);
- (gdb) b 426 【在426行设置断点】
- Breakpoint 2 at 0x804a247: file httpd.c, line 426.
- (gdb) c
- Continuing.
- Breakpoint 2, serve_file (client=4, filename=0xb63fdf4e "htdocs/index2.html") at httpd.c:426
- 426 resource = fopen(filename, "r");
- (gdb) p filename
- $2 = 0xb63fdf4e "htdocs/index2.html"
- (gdb) n
- 427 if (resource == NULL)
- (gdb) n
- 431 headers(client, filename);
- (gdb) n
- 432 cat(client, resource);
- (gdb) s 【进入cat里面看看】
- cat (client=4, resource=0xb6c00468) at httpd.c:170
- 170 {
- (gdb) l
- 165 * easier just to do something like pipe, fork, and exec("cat").
- 166 * Parameters: the client socket descriptor
- 167 * FILE pointer for the file to cat */
- 168 /**********************************************************************/
- 169 void cat(int client, FILE *resource)
- 170 {
- 171 char buf[1024];
- 172
- 173 fgets(buf, sizeof(buf), resource);
- 174 while (!feof(resource))
- (gdb) n
- 173 fgets(buf, sizeof(buf), resource);
- (gdb) n
- 174 while (!feof(resource))
- (gdb) p buf 【讲到了index2.html的一行,然后send】
- $3 = "<a href=\"http://10.108.222.96:54205/test.sh\">Display Date</a>\n", '\000' <repeats 306 times>, "\"\225^\267\000\000\000\000 \312q\267\000\320t\267 \000\000\000 \312q\267\304Re\267 \000\000\000El^\267\001\000\000\000\000\320t\267 \000\000\000\364\277q\267\360\331?\266V\003_\267\364\277q\267 \000\000\000 \312q\267\000\320t\267\000\000\000\000$k^\267 \312q\267\000\320t\267 ", '\000' <repeats 15 times>, "A\252\004\b\364\277q\267 \000\000\000\377\377\377\377\000\000\000\000\236\201^\267 ", '\000' <repeats 23 times>, " \312q\267U\205^\267 \312q\267\000\320t\267 ", '\000' <repeats 19 times>"\364, \277q\267\001\000\000\000R\252\004\b\000\000\000\000\343v^\267"...
- (gdb) n
- 176 send(client, buf, strlen(buf), 0);
- (gdb) n
- 177 fgets(buf, sizeof(buf), resource);
- (gdb) n
- 174 while (!feof(resource))
- (gdb) n
- 179 }
- (gdb) n
- serve_file (client=4, filename=0xb63fdf4e "htdocs/index2.html") at httpd.c:434
- 434 fclose(resource);
- (gdb) bt
- #0 serve_file (client=4, filename=0xb63fdf4e "htdocs/index2.html") at httpd.c:434
- #1 0x08048f83 in accept_request (client=4) at httpd.c:130
- #2 0xb7726d4c in start_thread () from /lib/i386-linux-gnu/libpthread.so.0
- #3 0xb7665b8e in clone () from /lib/i386-linux-gnu/libc.so.6
- (gdb) n
- 435 }
- (gdb) s
- accept_request (client=4) at httpd.c:139
- 139 close(client); <span style="background-color: rgb(255, 255, 255);">【直到运行在这里,浏览器的请求才会真正停止,意味着标签栏那个不断旋转的标志就停了】</span>
- (gdb) s
- 140 }
- (gdb) s
- 0xb7726d4c in start_thread () from /lib/i386-linux-gnu/libpthread.so.0
- (gdb) s
- Single stepping until exit from function start_thread,
- which has no line number information.
- [New Thread 0xb5bfdb40 (LWP 7656)]
- [Switching to Thread 0xb5bfdb40 (LWP 7656)]
- Breakpoint 1, accept_request (client=4) at httpd.c:64
- 64 numchars = get_line(client, buf, sizeof(buf));//从套接字中读取一行
- (gdb) n
- [Thread 0xb63feb40 (LWP 7655) exited]
- 65 i = 0; j = 0;
- (gdb) p buf
- $4 = "GET /favicon.ico HTTP/1.1\n", '\000' <repeats 997 times> 【再读一行时,竟读到favicon.ico,目前没弄明白这怎么回事】
- (gdb)
前面已说过,tinyhttpd目前就支持两种请求形式,纯get请求或者带?的get和直接POST请求。了解到源码htdocs目录下的cgi都是perl写的,不知读者你懂不懂,反正博主我不懂,所以就改一改,改成自己的需求,用shell写。正如index2.html所示:
<a href="http://10.108.222.96:54205/test.sh">Display Date</a>
test.sh脚本如下:
#!/bin/sh
#echo "Content-type:text/html"
echo
echo "<html><head><meta charset="utf-8"><title>MyTitle</title></head><body>"
time=`date`
echo "<p>Server Time:$time"
echo "</body></html>"
即包括服务器响应给客户的字符数据,顺便把服务器时间传过去。注意要加test.sh添加执行权限,才会被视为执行cgi程序,且href中的端口号要改为你具体的端口号,这里只是个示例。来看当在浏览器中点击“Display Date”时,服务器作出的响应:
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?
- (gdb) l execute_cgi 【为了节省空间,以下内容我删除了无关内容】
- warning: Source file is more recent than executable.
- 214 * Parameters: client socket descriptor
- 215 * path to the CGI script */
- 216 /**********************************************************************/
- 217 void execute_cgi(int client, const char *path,
- 218 const char *method, const char *query_string)
- 219 {
- 220 char buf[1024];
- 229
- 230 buf[0] = 'A'; buf[1] = '\0';
- 231 if (strcasecmp(method, "GET") == 0)
- (gdb) b 231 【在execute_cgi处设置断点】
- Breakpoint 1 at 0x8049555: file httpd.c, line 231.
- (gdb) c
- Continuing. 【当在浏览器发起请求时,serve_file被调用,但此时断点在execute_cgi处,所以此处没有反应直到鼠标点击链接】
- [New Thread 0xb7567b40 (LWP 7708)]
- [Thread 0xb7567b40 (LWP 7708) exited]
- [New Thread 0xb6bffb40 (LWP 7709)]
- [Thread 0xb6bffb40 (LWP 7709) exited]
- [New Thread 0xb63feb40 (LWP 7710)]
- [Switching to Thread 0xb63feb40 (LWP 7710)]
- Breakpoint 1, execute_cgi (client=4, path=0xb63fdf4e "htdocs/test.sh", method=0xb63fe14e "GET",
- query_string=0xb63fe255 "") at httpd.c:231
- 231 if (strcasecmp(method, "GET") == 0)
- (gdb) info args 【查看此函数调用参数值】
- client = 4
- path = 0xb63fdf4e "htdocs/test.sh" 【文件为test.sh脚本】
- method = 0xb63fe14e "GET"
- query_string = 0xb63fe255 ""
- 257
- 258 if (pipe(cgi_output) < 0) {
- 259 cannot_execute(client);
- 260 return;
- 261 }
- 262 if (pipe(cgi_input) < 0) {
- 263 cannot_execute(client);
- 264 return;
- 265 }
- 266
- (gdb) b 258 【在创建管道处设置断点】
- Breakpoint 2 at 0x804973e: file httpd.c, line 258.
- (gdb) c
- Continuing.
- Breakpoint 2, execute_cgi (client=4, path=0xb63fdf4e "htdocs/test.sh", method=0xb63fe14e "GET",
- query_string=0xb63fe255 "") at httpd.c:258
- 258 if (pipe(cgi_output) < 0) {
- (gdb) n
- 262 if (pipe(cgi_input) < 0) {
- (gdb) n
- 267 if ( (pid = fork()) < 0 ) {
- (gdb) l
- 262 if (pipe(cgi_input) < 0) {
- 263 cannot_execute(client);
- 264 return;
- 265 }
- 266
- 267 if ( (pid = fork()) < 0 ) {
- 268 cannot_execute(client);
- 269 return;
- 270 }
- 271 if (pid == 0) /* child: CGI script */
- (gdb) l
- 272 {
- 273 char meth_env[255];
- 274 char query_env[255];
- 275 char length_env[255];
- 276
- 277 dup2(cgi_output[1], 1);
- 278 dup2(cgi_input[0], 0);
- 279 close(cgi_output[0]);
- 280 close(cgi_input[1]);
- 281 sprintf(meth_env, "REQUEST_METHOD=%s", method);
- (gdb) l
- 282 putenv(meth_env);
- 283 if (strcasecmp(method, "GET") == 0) { 【我的测试例子虽说是get请求,但不需要设置什么环境变量】
- 284 sprintf(query_env, "QUERY_STRING=%s", query_string);
- 285 putenv(query_env);
- 286 }
- 287 else { /* POST */
- 288 sprintf(length_env, "CONTENT_LENGTH=%d", content_length);
- 289 putenv(length_env);
- 290 }
- 291 execl(path, path, NULL); 【子进程执行test.sh】
- (gdb) l
- 292 exit(0);
- 293 }
- 294
- 295 else { /* parent */
- 296 close(cgi_output[1]);
- 297 close(cgi_input[0]);
- 298 if (strcasecmp(method, "POST") == 0)
- 299 for (i = 0; i < content_length; i++) {
- 300 recv(client, &c, 1, 0);
- 301 write(cgi_input[1], &c, 1);
- (gdb) b 298 【由于子进程执行test.sh,父进程发送响应给浏览器,所以先进入父进程,看发的是什么】
- Breakpoint 3 at 0x80498ec: file httpd.c, line 298.
- (gdb) c
- Continuing.
- Breakpoint 3, execute_cgi (client=4, path=0xb63fdf4e "htdocs/test.sh", method=0xb63fe14e "GET",
- query_string=0xb63fe255 "") at httpd.c:298
- 298 if (strcasecmp(method, "POST") == 0)
- (gdb) n
- 304 while (read(cgi_output[0], &c, 1) > 0)
- (gdb) l
- 299 for (i = 0; i < content_length; i++) { 【如果是POST,则还要继续从cgi_input中读取数据体,它被导入到标准输入,从而经由管道进入cgi_output[1]】
- 300 recv(client, &c, 1, 0);
- 301 write(cgi_input[1], &c, 1);
- 302 }
- 303
- 304 while (read(cgi_output[0], &c, 1) > 0)
- 305 send(client, &c, 1, 0);
- 306
- 307 close(cgi_output[0]);
- 308 close(cgi_input[1]);
- (gdb) s 【单步从cgi_output[0]中读】
- 305 send(client, &c, 1, 0);
- (gdb) p c
- $1 = 10 '\n'
- (gdb) s
- 305 send(client, &c, 1, 0);
- (gdb) p c 【以下部分刚好读到的是test脚本的"<html"】
- $2 = 60 '<'
- (gdb) s
- 305 send(client, &c, 1, 0);
- (gdb) p c
- $3 = 104 'h'
- (gdb) s
- 305 send(client, &c, 1, 0);
- (gdb) p c
- $4 = 116 't'
- (gdb) s
- 305 send(client, &c, 1, 0);
- (gdb) p c
- $5 = 109 'm'
- (gdb) s
- 305 send(client, &c, 1, 0);
- (gdb) p c
- $6 = 108 'l'
- (gdb) l
- 300 recv(client, &c, 1, 0);
- 301 write(cgi_input[1], &c, 1);
- 302 }
- 303
- 304 while (read(cgi_output[0], &c, 1) > 0)
- 305 send(client, &c, 1, 0);
- 306
- 307 close(cgi_output[0]);
- 308 close(cgi_input[1]);
- 309 waitpid(pid, &status, 0);
- (gdb) b 307
- Breakpoint 4 at 0x80499be: file httpd.c, line 307.
- (gdb) c
- Continuing.
- Breakpoint 4, execute_cgi (client=4, path=0xb63fdf4e "htdocs/test.sh", method=0xb63fe14e "GET",
- query_string=0xb63fe255 "") at httpd.c:307
- 307 close(cgi_output[0]);
- (gdb) n
- 308 close(cgi_input[1]);
- (gdb) n
- 309 waitpid(pid, &status, 0);
- (gdb) n
- 311 }
- (gdb) p status
- $7 = 0
- (gdb) n
- accept_request (client=4) at httpd.c:139
- 139 close(client); <span style="background-color: rgb(255, 255, 255);">【直到这里,浏览器才显示了返回结果】</span>
- (gdb) n
- 140 }
- (gdb)
结果显示:
当然我在这里只是演示了其中的一种情况,至于情况如get请求带?查询的,POST请求带数据体的,只有靠读者自己去尝试了,博主暂时抛砖引玉于此。
呃,感觉讲解至此结束了呢。貌似还有一点点细节博主还得继续研究下,总之通过这个例子确实对Linux编程了解了更多了,感谢开源,哈哈!