sscanf_强大的数据读取-转换
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function <cstdio> sscanf int sscanf ( const char * s, const char * format, ...); Read formatted data from string Reads data from s and stores them according to parameter format into the locations given by the additional arguments, as if scanf was used, but reading from s instead of the standard input (stdin). The additional arguments should point to already allocated objects of the type specified by their corresponding format specifier within the format string. Parameters s C string that the function processes as its source to retrieve the data. format C string that contains a format string that follows the same specifications as format in scanf (see scanf for details). ... (additional arguments) Depending on the format string, the function may expect a sequence of additional arguments, each containing a pointer to allocated storage where the interpretation of the extracted characters is stored with the appropriate type. There should be at least as many of these arguments as the number of values stored by the format specifiers. Additional arguments are ignored by the function. Return Value On success, the function returns the number of items in the argument list successfully filled. This count can match the expected number of items or be less (even zero) in the case of a matching failure. In the case of an input failure before any data could be successfully interpreted, EOF is returned.
头文件
返回值
sscanf与scanf类似，都是用于输入的，只是后者以键盘(stdin)为输入源，前者以固定字符串为输入源。
格式控制符，类似于正则表达式：
支持集合操作
例子
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char buf[512];sscanf("123456","%s",buf);//此处buf是数组名，它的意思是将123456以%s的形式存入buf中！printf("%s\n",buf); |
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sscanf("123456","%4s",buf);printf("%s\n",buf); |
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sscanf("123456abcdedf","%[^a-z]",buf);printf("%s\n",buf); |
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sscanf("123456abcdedfBCDEF","%[1-9a-z]",buf);printf("%s\n",buf); |
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printf("%s\n",buf); |
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sscanf("123456abcdedfBCDEF","%[^A-Z]",buf);printf("%s\n",buf); |
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sscanf("iios/12DDWDFF@122","%*[^/]/%[^@]",buf);printf("%s\n",buf); |
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sscanf(“hello, world”,"%*s%s",buf);printf("%s\n",buf); |
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sscanf(“字符串1\t字符串2\t字符串3”,"%s%s%s",str1,str2,str3);printf("%s\t%s\t%s\n",str1,str2,str3); |
sscanf及sscanf_s的常用方法，原来安全版本的函数，对参数和缓冲边界做了检查，增加了返回值和抛出异常。这样增加了函数的安全性，减少了出错的几率。
同时这也意味着在使用这些函数时，有时你不得不输入更多的关于缓冲区大小的参数，多敲几下键盘能换来更少的麻烦，值得！
下面总结了sscanf的以及sscanf_s的常用方法，也体现了“_s”版本函数与原函数的特别之处：
1、sscanf和scanf的不同是输入来源，前者是一个字符串，后者则是标准输入设备
2、sscanf的使用，以解析时间字符串为例，将字符串“2009-01-02_11:12:13”解析为整型年月日时分秒
//定义
char cc;
tm tm_temp={0};
string stime("2009-01-02_11:12:13");
(1) 必须严格按照分隔符形式匹配填写，若遇到不匹配项则终止解析
sscanf(stime.c_str(), "%4d-%2d-%2d_%2d:%2d:%2d",
&tm_temp.tm_year,
&tm_temp.tm_mon,
&tm_temp.tm_mday,
&tm_temp.tm_hour,
&tm_temp.tm_min,
&tm_temp.tm_sec
);
(2) 可以不按照分割符号形式填写，字符数必须一致，例如可以正确解析“2009/01/02_11:12:13”
sscanf(stime.c_str(), "%4d%c%2d%c%2d%c%2d%c%2d%c%2d",
&tm_temp.tm_year, &cc,
&tm_temp.tm_mon, &cc,
&tm_temp.tm_mday, &cc,
&tm_temp.tm_hour, &cc,
&tm_temp.tm_min, &cc,
&tm_temp.tm_sec
);
(3) 可以不按照分割符号形式填写，字符数必须一致，同上，%1s可以等同于%c
sscanf(stime.c_str(), "%4d%1s%2d%1s%2d%1s%2d%1s%2d%1s%2d",
&tm_temp.tm_year, &cc,
&tm_temp.tm_mon, &cc,
&tm_temp.tm_mday, &cc,
&tm_temp.tm_hour, &cc,
&tm_temp.tm_min, &cc,
&tm_temp.tm_sec
);
(4) 可以不按照分割符形式和数量填写，类型必须一致，例如可以正确解析“2009/01/02___11:12:13”
这里使用了sscanf的正则表达式，与通用的正则表示类似但不完全相同，%*c表示忽略连续多个字符
sscanf(stime.c_str(), "%4d%*c%2d%*c%2d%*c%2d%*c%2d%*c%2d",
&tm_temp.tm_year,
&tm_temp.tm_mon,
&tm_temp.tm_mday,
&tm_temp.tm_hour,
&tm_temp.tm_min,
&tm_temp.tm_sec
);
3、sscanf_s的使用
//定义
char cc[2];
tm tm_temp={0};
string stime("2009-01-02_11:12:13");
(1) 与sscanf第一种方法相同，可以使用"%4d-%2d-%2d_%2d:%2d:%2d"格式匹配解析
sscanf_s(stime.c_str(), "%4d-%2d-%2d_%2d:%2d:%2d",
&tm_temp.tm_year,
&tm_temp.tm_mon,
&tm_temp.tm_mday,
&tm_temp.tm_hour,
&tm_temp.tm_min,
&tm_temp.tm_sec
);
(2) 使用%c格式对数据解析时，必须对相应的缓冲区增加长度参数，否则将会出错
sscanf_s(stime.c_str(), "%4d%c%2d%c%2d%c%2d%c%2d%c%2d",
&tm_temp.tm_year, &cc, 1,
&tm_temp.tm_mon, &cc, 1,
&tm_temp.tm_mday, &cc, 1,
&tm_temp.tm_hour, &cc, 1,
&tm_temp.tm_min, &cc, 1,
&tm_temp.tm_sec
);
(3) 使用%s格式对数据解析时，缓冲长度必须大于字符串长度，否则不予解析
sscanf_s(stime.c_str(), "%4d%1s%2d%1s%2d%1s%2d%1s%2d%1s%2d",
&tm_temp.tm_year, &cc, 2,
&tm_temp.tm_mon, &cc, 2,
&tm_temp.tm_mday, &cc, 2,
&tm_temp.tm_hour, &cc, 2,
&tm_temp.tm_min, &cc, 2,
&tm_temp.tm_sec
);
(4) 与sscanf一样，sscanf_s同样支持正则表达式
sscanf_s(stime.c_str(), "%4d%*c%2d%*c%2d%*c%2d%*c%2d%*c%2d",
&tm_temp.tm_year,
&tm_temp.tm_mon,
&tm_temp.tm_mday,
&tm_temp.tm_hour,
&tm_temp.tm_min,
&tm_temp.tm_sec
);
通过以上对比sscanf与sscanf_s的使用，可以看出后者对缓冲区安全有了更多的考虑，从而避免了许多不经意的烦恼。
大家都知道sscanf是一个很好用的函数，利用它可以从字符串中取出整数、浮点数和字符串等等。它的使用方法简单，特别对于整数和浮点数来说。但新手可 能并不知道处理字符串时的一些高级用法，这里做个简要说明吧。
string timeIn = "2016-09-17 09:48:13.560"; tm tm_timeIn = { 0 }; int timeOutMsecTemp = 0; sscanf_s(timeIn.c_str(), "%4d-%2d-%2d %2d:%2d:%2d.%3d", &tm_timeIn.tm_year, &tm_timeIn.tm_mon, &tm_timeIn.tm_mday, &tm_timeIn.tm_hour, &tm_timeIn.tm_min, &tm_timeIn.tm_sec, &timeInMsecTemp); tm_timeIn.tm_year -= 1900; //年份，指的是与1900年的差值 tm_timeIn.tm_mon -= 1; //月份，0代表1月，故应减去1 char dt[50]; ctime_s(dt, sizeof dt,&time_t_In); cout << dt << endl; //Sat Sep 17 09:48:13 2016\n char bat[50]; asctime_s(bat, sizeof bat, &tm_timeIn); cout << bat << endl;
