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ceil(3) — Linux manual page

NAME \|LIBRARY \|SYNOPSIS \|DESCRIPTION \|RETURN VALUE \|ERRORS \|ATTRIBUTES \|STANDARDS \|HISTORY \|SEE ALSO \|COLOPHON

ceil(3)                  Library Functions Manualceil(3)

NAME top

       ceil, ceilf, ceill - ceiling function: smallest integral value not       less than argument

LIBRARY top

       Math library (libm,-lm)

SYNOPSIS top

#include <math.h>double ceil(doublex);float ceilf(floatx);long double ceill(long doublex);   Feature Test Macro Requirements for glibc (seefeature_test_macros(7)):ceilf(),ceill():           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L               || /* Since glibc 2.19: */ _DEFAULT_SOURCE               || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION top

       These functions return the smallest integral value that is not       less thanx.       For example,ceil(0.5) is 1.0, andceil(-0.5) is 0.0.

RETURN VALUE top

       These functions return the ceiling ofx.       Ifx is integral, +0, -0, NaN, or infinite,x itself is returned.

ERRORS top

       No errors occur.

ATTRIBUTES top

       For an explanation of the terms used in this section, seeattributes(7).       ┌──────────────────────────────────────┬───────────────┬─────────┐       │Interface│Attribute│Value│       ├──────────────────────────────────────┼───────────────┼─────────┤       │ceil(),ceilf(),ceill()             │ Thread safety │ MT-Safe │       └──────────────────────────────────────┴───────────────┴─────────┘

STANDARDS top

       C11, POSIX.1-2008.

HISTORY top

       C99, POSIX.1-2001.       The variant returningdouble also conforms to SVr4, 4.3BSD, C89.       SUSv2 and POSIX.1-2001 contain text about overflow (which might       seterrno toERANGE, or raise anFE_OVERFLOWexception).  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.       The integral value returned by these functions may be too large to       store in an integer type (int,long, etc.).  To avoid an overflow,       which will produce undefined results, an application should       perform a range check on the returned value before assigning it to       an integer type.

COLOPHON top

       This page is part of theman-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 isnot       part of the original manual page), send a mail to       man-pages@man7.orgLinux man-pages 6.15            2025-05-17ceil(3)

Pages that refer to this page:abs(3), fabs(3), floor(3), lrint(3), lround(3), rint(3), round(3), roundup(3), trunc(3)

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