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

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

       ┌────────────────────────────────────────────────────────────────┬─────────────────────┬────────────────┐
       │ Interface                                                      │ Attribute           │ Value          │
       ├────────────────────────────────────────────────────────────────┼─────────────────────┼────────────────┤
       │                                                                │ Thread safety       │ MT-Safe locale │
       │                                                                ├─────────────────────┼────────────────┤
       │ strfromd(), strfromf(), strfroml()                             │ Async-signal safety │ AS-Unsafe heap │
       │                                                                ├─────────────────────┼────────────────┤
       │                                                                │ Async-cancel safety │ AC-Unsafe mem  │
       └────────────────────────────────────────────────────────────────┴─────────────────────┴────────────────┘

       Note: these attributes are preliminary.

       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.

   Formatoftheformatstring
       The  format  string  must  start with the character '%'.  This is followed by an optional precision which
       starts with the period character (.), followed  by  an  optional  decimal  integer.   If  no  integer  is
       specified  after  the  period  character, a precision of zero is used.  Finally, the format string should
       have one of the conversion specifiers a, A, e, E, f, F, g, or G.

       The conversion specifier is applied based on the floating-point type indicated by  the  function  suffix.
       Therefore,  unlike  snprintf(),  the  format  string  does  not  have  a  length modifier character.  See
       snprintf(3) for a detailed description of these conversion specifiers.

       The implementation conforms to the C99 standard on conversion of NaN and infinity values:

              If fp is a NaN, +NaN, or -NaN, and f (or a, e, g) is the conversion specifier, the  conversion  is
              to  "nan",  "nan",  or  "-nan",  respectively.  If F (or A, E, G) is the conversion specifier, the
              conversion is to "NAN" or "-NAN".

              Likewise if fp is infinity, it is converted to [-]inf or [-]INF.

       A malformed format string results in undefined behavior.

       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);

       Standard C library (libc, -lc)

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

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

       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.

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

Linux man-pages 6.9.1                              2024-06-15                                        strfromd(3)

       ISO/IEC TS 18661-1.

#include<stdlib.h>intstrfromd(charstr[restrict.n],size_tn,constchar*restrictformat,doublefp);intstrfromf(charstr[restrict.n],size_tn,constchar*restrictformat,floatfp);intstrfroml(charstr[restrict.n],size_tn,constchar*restrictformat,longdoublefp);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       strfromd(), strfromf(), strfroml():
           __STDC_WANT_IEC_60559_BFP_EXT__

strfromd()
       strfromf()
       strfroml()
              glibc 2.25.