365 lines
7.2 KiB
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365 lines
7.2 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML><HEAD><TITLE>Man page of STRFROMD</TITLE>
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</HEAD><BODY>
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<H1>STRFROMD</H1>
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Section: Linux Programmer's Manual (3)<BR>Updated: 2019-03-06<BR><A HREF="#index">Index</A>
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<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
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<A NAME="lbAB"> </A>
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<H2>NAME</H2>
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strfromd, strfromf, strfroml - convert a floating-point value into
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a string
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<PRE>
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<B>#include <<A HREF="file:///usr/include/stdlib.h">stdlib.h</A>></B>
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<B>int strfromd(char *restrict </B><I>str</I><B>, size_t </B><I>n</I><B>,</B>
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<B> const char *restrict </B><I>format</I><B>, double </B><I>fp</I><B>);</B>
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<B>int strfromf(char *restrict </B><I>str</I><B>, size_t </B><I>n</I><B>,</B>
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<B> const char *restrict </B><I>format</I><B>, float fp</B><I>);</I>
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<B>int strfroml(char *restrict </B><I>str</I><B>, size_t </B><I>n</I><B>,</B>
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<B> const char *restrict </B><I>format</I><B>, long double </B><I>fp</I><B>);</B>
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</PRE>
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<P>
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Feature Test Macro Requirements for glibc (see
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<B><A HREF="/cgi-bin/man/man2html?7+feature_test_macros">feature_test_macros</A></B>(7)):
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<P>
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<B>strfromd</B>(),
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<B>strfromf</B>(),
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<B>strfroml</B>():
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<DL COMPACT><DT id="1"><DD>
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__STDC_WANT_IEC_60559_BFP_EXT__
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</DL>
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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These functions convert a floating-point value,
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<I>fp</I>,
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into a string of characters,
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<I>str</I>,
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with a configurable
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<I>format</I>
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string.
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At most
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<I>n</I>
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characters are stored into
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<I>str</I>.
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<P>
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The terminating null character ('\0') is written if and only if
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<I>n</I>
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is sufficiently large, otherwise the written string is truncated at
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<I>n</I>
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characters.
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<P>
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The
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<B>strfromd</B>(),
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<B>strfromf</B>(),
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and
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<B>strfroml</B>()
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functions are equivalent to
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<P>
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snprintf(str, n, format, fp);
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<P>
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except for the
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<I>format</I>
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string.
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<A NAME="lbAE"> </A>
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<H3>Format of the format string</H3>
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The
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<I>format</I>
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string must start with the character '%'.
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This is followed by an optional precision which starts with the period
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character (.), followed by an optional decimal integer.
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If no integer is specified after the period character,
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a precision of zero is used.
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Finally, the format string should have one of the conversion specifiers
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<B>a</B>,
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<B>A</B>,
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<B>e</B>,
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<B>E</B>,
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<B>f</B>,
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<B>F</B>,
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<B>g</B>,
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or
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<B>G</B>.
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<P>
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The conversion specifier is applied based on the floating-point type
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indicated by the function suffix.
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Therefore, unlike
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<B>snprintf</B>(),
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the format string does not have a length modifier character.
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See
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<B><A HREF="/cgi-bin/man/man2html?3+snprintf">snprintf</A></B>(3)
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for a detailed description of these conversion specifiers.
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<P>
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The implementation conforms to the C99 standard on conversion of NaN and
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infinity values:
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<P>
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<DL COMPACT><DT id="2"><DD>
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If
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<I>fp</I>
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is a NaN, +NaN, or -NaN, and
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<B>f</B>
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(or
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<B>a</B>,
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<B>e</B>,
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<B>g</B>)
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is the conversion specifier, the conversion is to "nan", "nan", or "-nan",
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respectively.
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If
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<B>F</B>
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(or
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<B>A</B>,
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<B>E</B>,
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<B>G</B>)
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is the conversion specifier, the conversion is to "NAN" or "-NAN".
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<P>
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Likewise if
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<I>fp</I>
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is infinity, it is converted to [-]inf or [-]INF.
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</DL>
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<P>
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A malformed
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<I>format</I>
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string results in undefined behavior.
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<A NAME="lbAF"> </A>
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<H2>RETURN VALUE</H2>
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The
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<B>strfromd</B>(),
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<B>strfromf</B>(),
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and
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<B>strfroml</B>()
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functions return the number of characters that would have been written in
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<I>str</I>
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if
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<I>n</I>
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had enough space,
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not counting the terminating null character.
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Thus, a return value of
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<I>n</I>
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or greater means that the output was truncated.
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<A NAME="lbAG"> </A>
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<H2>VERSIONS</H2>
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The
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<B>strfromd</B>(),
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<B>strfromf</B>(),
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and
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<B>strfroml</B>()
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functions are available in glibc since version 2.25.
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<A NAME="lbAH"> </A>
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<H2>ATTRIBUTES</H2>
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For an explanation of the terms used in this section, see
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<B><A HREF="/cgi-bin/man/man2html?7+attributes">attributes</A></B>(7)
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and the
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<B>POSIX Safety Concepts</B>
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section in GNU C Library manual.
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<P>
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<TABLE BORDER>
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<TR VALIGN=top><TD><B>Interface</B></TD><TD><B>Attribute</B></TD><TD><B>Value</B><BR></TD></TR>
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<TR VALIGN=top><TD VALIGN=center ROWSPAN=2>
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<B>strfromd</B>(),
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<B>strfromf</B>(),
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<B>strfroml</B>()
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</TD><TD>Thread safety</TD><TD>MT-Safe locale<BR></TD></TR>
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<TR VALIGN=top><TD>Asynchronous signal safety</TD><TD>AS-Unsafe heap</TD></TR>
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<TR VALIGN=top><TD>Asynchronous cancellation safety</TD><TD>AC-Unsafe mem</TD></TR>
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</TABLE>
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<P>
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Note: these attributes are preliminary.
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<A NAME="lbAI"> </A>
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<H2>CONFORMING TO</H2>
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C99, ISO/IEC TS 18661-1.
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<A NAME="lbAJ"> </A>
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<H2>NOTES</H2>
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The
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<B>strfromd</B>(),
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<B>strfromf</B>(),
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and
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<B>strfroml</B>()
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functions take account of the
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<B>LC_NUMERIC</B>
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category of the current locale.
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<A NAME="lbAK"> </A>
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<H2>EXAMPLES</H2>
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To convert the value 12.1 as a float type to a string using decimal
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notation, resulting in "12.100000":
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<P>
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#define __STDC_WANT_IEC_60559_BFP_EXT__
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#include <<A HREF="file:///usr/include/stdlib.h">stdlib.h</A>>
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int ssize = 10;
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char s[ssize];
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strfromf(s, ssize, "%f", 12.1);
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<P>
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To convert the value 12.3456 as a float type to a string using
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decimal notation with two digits of precision, resulting in "12.35":
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<P>
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#define __STDC_WANT_IEC_60559_BFP_EXT__
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#include <<A HREF="file:///usr/include/stdlib.h">stdlib.h</A>>
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int ssize = 10;
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char s[ssize];
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strfromf(s, ssize, "%.2f", 12.3456);
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<P>
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To convert the value 12.345e19 as a double type to a string using
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scientific notation with zero digits of precision, resulting in "1E+20":
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<P>
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#define __STDC_WANT_IEC_60559_BFP_EXT__
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#include <<A HREF="file:///usr/include/stdlib.h">stdlib.h</A>>
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int ssize = 10;
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char s[ssize];
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strfromd(s, ssize, "%.E", 12.345e19);
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<A NAME="lbAL"> </A>
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<H2>SEE ALSO</H2>
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<B><A HREF="/cgi-bin/man/man2html?3+atof">atof</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+snprintf">snprintf</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+strtod">strtod</A></B>(3)
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<A NAME="lbAM"> </A>
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<H2>COLOPHON</H2>
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This page is part of release 5.05 of the Linux
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<I>man-pages</I>
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project.
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A description of the project,
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information about reporting bugs,
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and the latest version of this page,
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can be found at
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<A HREF="https://www.kernel.org/doc/man-pages/.">https://www.kernel.org/doc/man-pages/.</A>
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<P>
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<HR>
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<A NAME="index"> </A><H2>Index</H2>
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<DL>
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<DT id="3"><A HREF="#lbAB">NAME</A><DD>
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<DT id="4"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="5"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DL>
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<DT id="6"><A HREF="#lbAE">Format of the format string</A><DD>
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</DL>
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<DT id="7"><A HREF="#lbAF">RETURN VALUE</A><DD>
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<DT id="8"><A HREF="#lbAG">VERSIONS</A><DD>
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<DT id="9"><A HREF="#lbAH">ATTRIBUTES</A><DD>
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<DT id="10"><A HREF="#lbAI">CONFORMING TO</A><DD>
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<DT id="11"><A HREF="#lbAJ">NOTES</A><DD>
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<DT id="12"><A HREF="#lbAK">EXAMPLES</A><DD>
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<DT id="13"><A HREF="#lbAL">SEE ALSO</A><DD>
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<DT id="14"><A HREF="#lbAM">COLOPHON</A><DD>
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</DL>
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<HR>
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This document was created by
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<A HREF="/cgi-bin/man/man2html">man2html</A>,
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using the manual pages.<BR>
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Time: 00:05:58 GMT, March 31, 2021
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