mirror of https://github.com/mkerrisk/man-pages
141 lines
3.9 KiB
Groff
141 lines
3.9 KiB
Groff
.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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.\"
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.\" %%%LICENSE_START(VERBATIM)
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\" %%%LICENSE_END
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.\"
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.\" References consulted:
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.\" Linux libc source code
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.\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
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.\" 386BSD man pages
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.\" Modified Sat Jul 24 19:40:39 1993 by Rik Faith (faith@cs.unc.edu)
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.\" Modified Fri Jun 25 12:10:47 1999 by Andries Brouwer (aeb@cwi.nl)
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.\"
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.TH ECVT 3 2013-07-04 "" "Linux Programmer's Manual"
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.SH NAME
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ecvt, fcvt \- convert a floating-point number to a string
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.SH SYNOPSIS
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.B #include <stdlib.h>
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.sp
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.BI "char *ecvt(double " number ", int " ndigits ", int *" decpt ,
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.BI "int *" sign );
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.sp
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.BI "char *fcvt(double " number ", int " ndigits ", int *" decpt ,
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.BI "int *" sign );
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.sp
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.in -4n
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Feature Test Macro Requirements for glibc (see
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.BR feature_test_macros (7)):
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.in
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.sp
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.BR ecvt (),
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.BR fcvt ():
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.ad l
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.RS 4
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.PD 0
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.TP 4
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Since glibc 2.12:
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.nf
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_SVID_SOURCE ||
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(_XOPEN_SOURCE\ >=\ 500 ||
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_XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED) &&
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!(_POSIX_C_SOURCE\ >=\ 200112L || _XOPEN_SOURCE\ >=\ 600)
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.fi
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.TP 4
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Before glibc 2.12:
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_SVID_SOURCE || _XOPEN_SOURCE\ >=\ 500 ||
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_XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
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.PD
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.RE
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.ad b
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.SH DESCRIPTION
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The
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.BR ecvt ()
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function converts \fInumber\fP to a null-terminated
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string of \fIndigits\fP digits (where \fIndigits\fP is reduced to a
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system-specific limit determined by the precision of a
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.IR double ),
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and returns a pointer to the string.
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The high-order digit is nonzero, unless
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.I number
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is zero.
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The low order digit is rounded.
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The string itself does not contain a decimal point; however,
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the position of the decimal point relative to the start of the string
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is stored in \fI*decpt\fP.
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A negative value for \fI*decpt\fP means that
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the decimal point is to the left of the start of the string.
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If the sign of
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\fInumber\fP is negative, \fI*sign\fP is set to a nonzero value,
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otherwise it is set to 0.
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If
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.I number
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is zero, it is unspecified whether \fI*decpt\fP is 0 or 1.
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.PP
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The
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.BR fcvt ()
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function is identical to
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.BR ecvt (),
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except that
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\fIndigits\fP specifies the number of digits after the decimal point.
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.SH RETURN VALUE
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Both the
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.BR ecvt ()
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and
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.BR fcvt ()
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functions return a pointer to a
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static string containing the ASCII representation of \fInumber\fP.
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The static string is overwritten by each call to
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.BR ecvt ()
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or
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.BR fcvt ().
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.SH ATTRIBUTES
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.SS Multithreading (see pthreads(7))
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The
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.BR ecvt ()
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and
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.BR fcvt ()
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functions are not thread-safe.
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.SH CONFORMING TO
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SVr2;
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marked as LEGACY in POSIX.1-2001.
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POSIX.1-2008 removes the specifications of
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.BR ecvt ()
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and
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.BR fcvt (),
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recommending the use of
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.BR sprintf (3)
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instead (though
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.BR snprintf (3)
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may be preferable).
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.SH NOTES
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Linux libc4 and libc5 specified the type of
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.I ndigits
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as
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.IR size_t .
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Not all locales use a point as the radix character ("decimal point").
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.SH SEE ALSO
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.BR ecvt_r (3),
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.BR gcvt (3),
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.BR qecvt (3),
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.BR setlocale (3),
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.BR sprintf (3)
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