NAME¶

strfromd, strfromf, strfroml - convert a floating-point value into a string

LIBRARY¶

Standard C library (libc, -lc)

SYNOPSIS¶

#include <stdlib.h>

int strfromd(char str[restrict .n], size_t n,
             const char *restrict format, double fp);
int strfromf(char str[restrict .n], size_t n,
             const char *restrict format, float fp);
int strfroml(char str[restrict .n], size_t n,
             const char *restrict format, long double fp);

strfromd(), strfromf(), strfroml():

    __STDC_WANT_IEC_60559_BFP_EXT__

DESCRIPTION¶

These functions convert a floating-point value, fp, into a string of characters, str, with a configurable format string. At most n characters are stored into str.

The terminating null byte ('\0') is written if and only if n is sufficiently large, otherwise the written string is truncated at n characters.

The strfromd(), strfromf(), and strfroml() functions are equivalent to

snprintf(str, n, format, fp);

except for the format string.

RETURN VALUE¶

The strfromd(), strfromf(), and strfroml() functions return the number of characters that would have been written in str if n had enough space, not counting the terminating null byte. Thus, a return value of n or greater means that the output was truncated.

ATTRIBUTES¶

For an explanation of the terms used in this section, see attributes(7) and the POSIX Safety Concepts section in GNU C Library manual.

Note: these attributes are preliminary.

STANDARDS¶

ISO/IEC TS 18661-1.

VERSIONS¶

strfromd()

strfromf()

strfroml()

glibc 2.25.

NOTES¶

These functions take account of the LC_NUMERIC category of the current locale.

EXAMPLES¶

To convert the value 12.1 as a float type to a string using decimal notation, resulting in "12.100000":

#define __STDC_WANT_IEC_60559_BFP_EXT__
#include <stdlib.h>
int ssize = 10;
char s[ssize];
strfromf(s, ssize, "%f", 12.1);

To convert the value 12.3456 as a float type to a string using decimal notation with two digits of precision, resulting in "12.35":

#define __STDC_WANT_IEC_60559_BFP_EXT__
#include <stdlib.h>
int ssize = 10;
char s[ssize];
strfromf(s, ssize, "%.2f", 12.3456);

To convert the value 12.345e19 as a double type to a string using scientific notation with zero digits of precision, resulting in "1E+20":

#define __STDC_WANT_IEC_60559_BFP_EXT__
#include <stdlib.h>
int ssize = 10;
char s[ssize];
strfromd(s, ssize, "%.E", 12.345e19);

SEE ALSO¶

atof(3), snprintf(3), strtod(3)