Converting float to char*

How can I convert a float value to char* in C language?

7 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.

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

sprintf: (from MSDN)

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); 

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.

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); 

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);