c - 将浮点数转换为 char*

Question

如何将float值转换char*为C语言？

Answer 1

char buffer[64];
int ret = snprintf(buffer, sizeof buffer, "%f", myFloat);

if (ret < 0) {
    return EXIT_FAILURE;
}
if (ret >= sizeof buffer) {
    /* Result was truncated - resize the buffer and retry.
}

这将存储 in 的字符串表示myFloat形式myCharPointer。不过，请确保绳子足够大以容纳它。

snprintf是一个更好的选择，sprintf因为它保证它永远不会超过您在参数 2 中提供的缓冲区的大小。

Answer 2

char array[10];
sprintf(array, "%f", 3.123);

sprintf：（来自 MSDN）

Answer 3

在阿杜诺：

//temporarily holds data from vals
char charVal[10];                

//4 is mininum width, 3 is precision; float value is copied onto buff
dtostrf(123.234, 4, 3, charVal);

monitor.print("charVal: ");
monitor.println(charVal);

Answer 4

Long after accept answer.

Use sprintf(), or related functions, as many others have answers suggested, but use a better format specifier.

Using "%.*e", code solves various issues:

• The maximum buffer size needed is far more reasonable, like 18 for float (see below). With "%f", sprintf(buf, "%f", FLT_MAX); could need 47+. sprintf(buf, "%f", DBL_MAX); may need 317+ char.

• Using ".*" allows code to define the number of decimal places needed to distinguish a string version of float x and it next highest float. For deatils, see Printf width specifier to maintain precision of floating-point value

• Using "%e" allows code to distinguish small floats from each other rather than all printing "0.000000" which is the result when |x| < 0.0000005.

Example usage

#include <float.h>
#define FLT_STRING_SIZE (1+1+1+(FLT_DECIMAL_DIG-1)+1+1+ 4   +1)
                     //  - d .  dddddddd           e - dddd \0

char buf[FLT_STRING_SIZE];
sprintf(buf, "%.*e", FLT_DECIMAL_DIG-1, some_float);

Ideas:
IMO, better to use 2x buffer size for scratch pads like buf[FLT_STRING_SIZE*2].
For added robustness, use snprintf().

---

As a 2nd alterative consider "%.*g". It is like "%f" for values exponentially near 1.0 and like "%e" for others.

Answer 5

char* str=NULL;
int len = asprintf(&str, "%g", float_var);
if (len == -1)
  fprintf(stderr, "Error converting float: %m\n");
else
  printf("float is %s\n", str);
free(str);

Answer 6

typedef union{
    float a;
    char b[4];
} my_union_t;

您可以逐字节访问浮点数据值，并通过 8 位输出缓冲区（例如 USART）将其发送而无需强制转换。

Answer 7

char array[10];
snprintf(array, sizeof(array), "%f", 3.333333);