[C语言]字符串与其他类型间的转换

Plux posted @ 2011年6月06日 16:26 in C/C++ with tags c/c++ , 2397 阅读

字符串->其他类型:sscanf(const char *src, const char *format, ... )

这个函数和scanf(const char *format, ...)类似,但不同的是,sscanf()是把字符串src当作输入,然后从中提取需要的信息的。所以,事实上format参数的运用和我们从标准输入(键盘)那里获取参数是相似的。

例如:

由字符串提取整数(十进制):

char *src="2"; int i;
sscanf(src, "%d", &i); /* i = 2 */

从字符串提取浮点数:

char *src="2.2"; float f;
sscanf(src, "%f", &f); /* f = 2.2 */

从字符串提取字符串:

char *src="abc def"; char a[4], b[4];
sscanf(src, "%s %s", a, b); /* a="abc". b="def" */

这个是比较有意思的应用。这样,我们就可以很方便地分割字符了。

而使用这个函数时,不需注意后面的参数是指针而不是整数或者其他数值类型。


其他类型->字符串:sprintf(const char *dest, const char *format, ...)

这个函数和sscanf是相对应的。因此,可以类比printf()的用法来得出这个函数的用法,就是从把后文format的内容复制到src中而不是标准输出而已。

例如:

十进制整数到字符串:

char dest[3]; int i=3;
sprintf(dest, "%d", i); /* dest = "3"; */

浮点数到字符串:

char dest[5]; float f=3.3f;
sprintf(dest, "%f", f); /* dest = "3.3" */

字符串到字符串:

char dest[10]; char *a="abc", *b="def";
sprintf(dest, "%s %s", a, b); /* dest = "abc def" */

这样也可以当作字符串合并函数用~

而使用sprintf()时必须注意目标字符串的长度。

以上的仅仅列举了常用的一些类型转换,至于其他类型,只要修改格式中的%x就好了(x替换为其他类型的代表字符,叫做类型转换符吧,另外注意‘x’本身其实也代表一种类型)。作为一个参考的文档,把Linux Programmer's Manual上关于sscanf()和sprintf()的文档也翻译一下吧~

类型转换符:(就是修饰在‘%’后面的字符,作为后面传入参数的类型提示。)

  • d - 十进制整数,对应int类型指针
  • i - 整数,对应int类型;与d不同的是,如果字符串中的整数以‘0x’等暗示进位制的前缀时,它会自动识别为该进制下的整数。
  • o - 八进制整数,对应int类型指针
  • u - 无符号十进制整数,对应unsigned int类型指针
  • x - 十六进制整数,对应int类型指针
  • f - 浮点数,对应float类型指针
  • s - 连续字符串(没有空格分开),对应char的指针
  • c - 指定长度的字符串,例如:10c读取10个字符到字符串中。对应char指针
  • [] - 匹配正则表达式……
  • ……

 

类型修饰符:(就是在前面类型转换符前面加的修饰符)

  • h - 修饰短整数
  • l - 长整数
  • L - 更精确的double类型(也就是long double)
  • ……

另外,这两个函数就存在于stdio.h中,属于标准函数。更详细的内容,例如正则表达式的使用,参见Linux Programmer's Manual……

 

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