How can I convert a float value to char* in C language?
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11You'll need to be more specific. What do you want - a textual representation of the decimal value of the float? A stream of bytes you can pass around easily and use to reconstitute the float later?crazyscot– crazyscot2010-06-07 10:46:55 +00:00Commented Jun 7, 2010 at 10:46
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9 Answers
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.
}
That will store the string representation of myFloat in myCharPointer. Make sure that the string is large enough to hold it, though.
snprintf is a better option than sprintf as it guarantees it will never write past the size of the buffer you supply in argument 2.
Comments
In Arduino:
//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);
Comments
char array[10];
sprintf(array, "%f", 3.123);
sprintf: (from MSDN)
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 with
"%.*e", like 18 forfloat(see below). With"%f", (think fixed-point),sprintf(buf, "%f", FLT_MAX);could need 47+char.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 offloat xand it next highestfloat. For details, see printf width specifier to maintain precision of floating-point valueUsing
"%e"allows code to distinguish smallfloats from each other rather than all printing"0.000000"which is the result when|x| < 0.0000005with"%f".
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.
Comments
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);
1 Comment
ShinTakezou
+1 even though it must specified it is a GNU extension afaik. (asprintf is a GNU ext I mean)
typedef union{
float a;
char b[4];
} my_union_t;
You can access to float data value byte by byte and send it through 8-bit output buffer (e.g. USART) without casting.
char array[10];
snprintf(array, sizeof(array), "%f", 3.333333);
Comments
// float arr to bytes
int arr_len = 3;
float x[3] = {1.123, 2.123, 3.123};
char* bytes = new char[arr_len * sizeof(float)];
memcpy(bytes, x, arr_len * sizeof(float));
// bytes to float arr
float y[3];
memcpy(y, bytes, arr_len * sizeof(float));
1 Comment
Michael M.
Please provide more supporting information to your answer.
