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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | STANDARDS | HISTORY | SEE ALSO | COLOPHON |
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modf(3) Library Functions Manual modf(3)
modf, modff, modfl - extract signed integral and fractional values
from floating-point number
Math library (libm, -lm)
#include <math.h>
double modf(double x, double *iptr);
float modff(float x, float *iptr);
long double modfl(long double x, long double *iptr);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
modff(), modfl():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
These functions break the argument x into an integral part and a
fractional part, each of which has the same sign as x. The
integral part is stored in the location pointed to by iptr.
These functions return the fractional part of x.
If x is a NaN, a NaN is returned, and *iptr is set to a NaN.
If x is positive infinity (negative infinity), +0 (-0) is
returned, and *iptr is set to positive infinity (negative
infinity).
No errors occur.
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────────────────────────────┬───────────────┬─────────┐
│ Interface │ Attribute │ Value │
├──────────────────────────────────────┼───────────────┼─────────┤
│ modf(), modff(), modfl() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘
C11, POSIX.1-2008.
C99, POSIX.1-2001.
The variant returning double also conforms to SVr4, 4.3BSD, C89.
frexp(3), ldexp(3)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.15.tar.gz
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⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2025-08-11. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
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[email protected]
Linux man-pages 6.15 2025-05-17 modf(3)
Pages that refer to this page: frexp(3), ldexp(3)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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