.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
.\"
.\" %%%LICENSE_START(VERBATIM)
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.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\"
.\" Permission is granted to copy and distribute modified versions of this
.\" manual under the conditions for verbatim copying, provided that the
.\" entire resulting derived work is distributed under the terms of a
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.\" Since the Linux kernel and libraries are constantly changing, this
.\" manual page may be incorrect or out-of-date.  The author(s) assume no
.\" responsibility for errors or omissions, or for damages resulting from
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.\" References consulted:
.\"     Linux libc source code
.\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
.\"     386BSD man pages
.\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
.\" Modified 2002-07-27 by Walter Harms
.\" 	(walter.harms@informatik.uni-oldenburg.de)
.\"
.TH MODF 3  2016-03-15 ""  "Linux Programmer's Manual"
.SH NAME
modf, modff, modfl \- extract signed integral and fractional values from
floating-point number
.SH SYNOPSIS
.nf
.B #include <math.h>
.sp
.BI "double modf(double " x ", double *" iptr );
.br
.BI "float modff(float " x ", float *" iptr );
.br
.BI "long double modfl(long double " x ", long double *" iptr );
.fi
.sp
Link with \fI\-lm\fP.
.sp
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
.sp
.ad l
.BR modf (),
.BR modfl ():
.RS 4
_ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
    || /* Since glibc 2.19: */ _DEFAULT_SOURCE
    || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
.RE
.ad
.SH DESCRIPTION
These functions break the argument
.I x
into an integral
part and a fractional part, each of which has the same sign as
.IR x .
The integral part is stored in the location pointed to by
.IR iptr .
.SH RETURN VALUE
These functions return the fractional part of
.IR x .

If
.I x
is a NaN, a NaN is returned, and
.IR *iptr
is set to a NaN.

If
.I x
is positive infinity (negative infinity), +0 (\-0) is returned, and
.IR *iptr
is set to positive infinity (negative infinity).
.SH ERRORS
No errors occur.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lbw24 lb lb
l l l.
Interface	Attribute	Value
T{
.BR modf (),
.BR modff (),
.BR modfl ()
T}	Thread safety	MT-Safe
.TE
.SH CONFORMING TO
C99, POSIX.1-2001, POSIX.1-2008.

The variant returning
.I double
also conforms to
SVr4, 4.3BSD, C89.
.SH SEE ALSO
.BR frexp (3),
.BR ldexp (3)
.SH COLOPHON
This page is part of release 4.10 of the Linux
.I man-pages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
\%https://www.kernel.org/doc/man\-pages/.