float strtof ( const char* restrict str, char** restrict str_end );
(1) (since C99) (2)double strtod ( const char* str, char** str_end );
(until C99)double strtod ( const char* restrict str, char** restrict str_end );
(since C99)long double strtold( const char* restrict str, char** restrict str_end );
(3) (since C99)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:
e or E followed with optional minus or plus sign and nonempty sequence of decimal digits (defines exponent to base 10)0x or 0Xp or P followed with optional minus or plus sign and nonempty sequence of decimal digits (defines exponent to base 2)INF or INFINITY ignoring caseNAN or NAN(char_sequence ) ignoring case of the NAN part. char_sequence can only contain digits, Latin letters, and underscores. The result is a quiet NaN floating-point value.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 str - pointer to the null-terminated byte string to be interpreted str_end - pointer to a pointer to character [edit] Return valueFloating-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, â0â 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));
}
Possible output:
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
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