strtof, strtod, strtold

Interprets a floating-point value in a byte string pointed to by str.

Function discards any whitespace characters (as determined by isspace ) until first non-whitespace character is found. Then it takes as many characters as possible to form a valid floating-point representation and converts them to a floating-point value. The valid floating-point value can be one of the following:

• decimal floating-point expression. It consists of the following parts:

• (optional) plus or minus sign
• nonempty sequence of decimal digits optionally containing decimal-point character (as determined by the current C locale) (defines significand)
• (optional) e or E followed with optional minus or plus sign and nonempty sequence of decimal digits (defines exponent to base 10)

• any other expression that may be accepted by the currently installed C locale.

The functions sets the pointer pointed to by str_end to point to the character past the last character interpreted. If str_end is a null pointer, it is ignored.

[edit] Parameters

[edit] Return value

Floating-point value corresponding to the contents of str on success. If the converted value falls out of range of corresponding return type, range error occurs (errno is set to ERANGE ) and HUGE_VAL , HUGE_VALF or HUGE_VALL is returned. If no conversion can be performed, ​0​ is returned.

[edit] Example

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
 
int main(void)
{
 // parsing with error handling
 const char* p = "111.11 -2.22 Nan nan(2) inF 0X1.BC70A3D70A3D7P+6 1.18973e+4932zzz";
 printf ("Parsing '%s':\n", p);
 char* end = NULL ;
 for (double f = strtod(p, &end); p != end; f = strtod(p, &end))
 {
 printf ("'%.*s' -> ", (int)(end - p), p);
 p = end;
 if (errno == ERANGE )
 {
 printf ("range error, got ");
 errno = 0;
 }
 printf ("%f\n", f);
 }
 
 // parsing without error handling
 printf ("\" -0.0000000123junk\" -->  %g\n", strtod(" -0.0000000123junk", NULL ));
 printf ("\"junk\" -->  %g\n", strtod("junk", NULL ));
}

Parsing '111.11 -2.22 Nan nan(2) inF 0X1.BC70A3D70A3D7P+6 1.18973e+4932zzz':
'111.11' -> 111.110000
' -2.22' -> -2.220000
' Nan' -> nan
' nan(2)' -> nan
' inF' -> inf
' 0X1.BC70A3D70A3D7P+6' -> 111.110000
' 1.18973e+4932' -> range error, got inf
" -0.0000000123junk" --> -1.23e-08
"junk" --> 0

[edit] References

[edit] See also

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