strfromd(3) - Linux manual page (original) (raw)
strfromd(3) Library Functions Manual strfromd(3)
NAME top
strfromd, strfromf, strfroml - convert a floating-point value into
a stringLIBRARY top
Standard C library (_libc_, _-lc_)SYNOPSIS top
**#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_**);**Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
**strfromd**(), **strfromf**(), **strfroml**():
__STDC_WANT_IEC_60559_BFP_EXT__DESCRIPTION top
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.Format of the format string 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)](../man3/snprintf.3.html) 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.RETURN VALUE top
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 top
For an explanation of the terms used in this section, see
[attributes(7)](../man7/attributes.7.html) and the **POSIX Safety Concepts** 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.STANDARDS top
ISO/IEC TS 18661-1.VERSIONS top
**strfromd**()
**strfromf**()
**strfroml**()
glibc 2.25.NOTES top
These functions take account of the **LC_NUMERIC** category of the
current locale.EXAMPLES top
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 top
[atof(3)](../man3/atof.3.html), [snprintf(3)](../man3/snprintf.3.html), [strtod(3)](../man3/strtod.3.html)COLOPHON top
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man-pages@man7.orgLinux man-pages 6.10 2024-07-23 strfromd(3)
Pages that refer to this page:atof(3), printf(3), strtod(3)