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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | CONFORMING TO | NOTES | SEE ALSO | COLOPHON |
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CEIL(3) Linux Programmer's Manual CEIL(3)
ceil, ceilf, ceill - ceiling function: smallest integral value not
less than argument
#include <math.h>
double ceil(double x);
float ceilf(float x);
long double ceill(long double x);
Link with -lm.
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
ceilf(), ceill():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
These functions return the smallest integral value that is not less
than x.
For example, ceil(0.5) is 1.0, and ceil(-0.5) is 0.0.
These functions return the ceiling of x.
If x is integral, +0, -0, NaN, or infinite, x itself is returned.
No errors occur. POSIX.1-2001 documents a range error for overflows,
but see NOTES.
For an explanation of the terms used in this section, see
attributes(7).
┌─────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├─────────────────────────┼───────────────┼─────────┤
│ceil(), ceilf(), ceill() │ Thread safety │ MT-Safe │
└─────────────────────────┴───────────────┴─────────┘
C99, POSIX.1-2001, POSIX.1-2008.
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 is 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
128 (respectively, 1024), and the number of mantissa bits is 24
(respectively, 53).)
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.
floor(3), lrint(3), nearbyint(3), rint(3), round(3), trunc(3)
This page is part of release 4.15 of the Linux 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/.
2017-09-15 CEIL(3)
Pages that refer to this page: abs(3), fabs(3), floor(3), lrint(3), lround(3), rint(3), round(3), trunc(3)
Copyright and license for this manual page
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