# 标准库stdlib.h函数atof()

**原型**

```c
double atof(const char * str);
```

**说明**

转换字符串为双精度浮点型，这个函数从非空白字符串开始直到第一个空格位置，可以包含其他字符，如果一个数字字符都没有，那么返回0.0值。如果开始是非数字，也会返回0.0值。其中需要注意的是科学技术法的浮点数也行哦。

**实例**

```c
#include <stdio.h>      /* printf, fgets */
#include <stdlib.h>     /* atof */
#include <math.h>       /* sin */

int main ()
{
  double n,m;
  double pi=3.1415926535;
  char buffer[256];
  printf ("Enter degrees: ");
  fgets (buffer,256,stdin);
  n = atof (buffer);
  m = sin (n*pi/180);
  printf ("The sine of %f degrees is %f\n" , n, m);
  return 0;
}
```


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