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Man page of CEIL
CEIL
Section: Linux Programmer's Manual (3)
Updated: 2016-03-15
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NAME
ceil, ceilf, ceill - ceiling function: smallest integral value not
less than argument
SYNOPSIS
#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
DESCRIPTION
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.
RETURN VALUE
These functions return the ceiling of
x.
If
x
is integral, +0, -0, NaN, or infinite,
x
itself is returned.
ERRORS
No errors occur.
POSIX.1-2001 documents a range error for overflows, but see NOTES.
ATTRIBUTES
For an explanation of the terms used in this section, see
attributes(7).
| Interface | Attribute | Value
|
|
ceil(),
ceilf(),
ceill()
| Thread safety | MT-Safe
|
CONFORMING TO
C99, POSIX.1-2001, POSIX.1-2008.
The variant returning
double
also conforms to
SVr4, 4.3BSD, C89.
NOTES
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.
SEE ALSO
floor(3),
lrint(3),
nearbyint(3),
rint(3),
round(3),
trunc(3)
COLOPHON
This page is part of release 4.09 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/.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- ATTRIBUTES
-
- CONFORMING TO
-
- NOTES
-
- SEE ALSO
-
- COLOPHON
-
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