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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | STANDARDS | HISTORY | SEE ALSO | COLOPHON |
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floor(3) Library Functions Manual floor(3)
floor, floorf, floorl - largest integral value not greater than
argument
Math library (libm, -lm)
#include <math.h>
double floor(double x);
float floorf(float x);
long double floorl(long double x);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
floorf(), floorl():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
These functions return the largest integral value that is not
greater than x.
For example, floor(0.5) is 0.0, and floor(-0.5) is -1.0.
These functions return the floor of x.
If x is integral, +0, -0, NaN, or an infinity, x itself is
returned.
No errors occur.
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────────────────────────────┬───────────────┬─────────┐
│ Interface │ Attribute │ Value │
├──────────────────────────────────────┼───────────────┼─────────┤
│ floor(), floorf(), floorl() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘
C11, POSIX.1-2008.
C99, POSIX.1-2001.
The variant returning double also conforms to SVr4, 4.3BSD, C89.
SUSv2 and POSIX.1-2001 contain text about overflow (which might
set errno to ERANGE, or raise an FE_OVERFLOW exception). In
practice, the result cannot overflow on any current machine, so
this error-handling stuff was just nonsense. (More precisely,
overflow can happen only when the maximum value of the exponent is
smaller than the number of mantissa bits. For the IEEE-754
standard 32-bit and 64-bit floating-point numbers the maximum
value of the exponent is 127 (respectively, 1023), and the number
of mantissa bits including the implicit bit is 24 (respectively,
53).) This was removed in POSIX.1-2008.
ceil(3), lrint(3), nearbyint(3), rint(3), round(3), trunc(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
fetched from
⟨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
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
[email protected]
Linux man-pages 6.15 2025-05-17 floor(3)
Pages that refer to this page: abs(3), ceil(3), fabs(3), lrint(3), lround(3), rint(3), round(3), roundup(3), trunc(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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