CEIL(3P) POSIX Programmer's Manual CEIL(3P)PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the corresponding
Linux manual page for details of Linux behavior), or the interface may
not be implemented on Linux.
ceil, ceilf, ceill - ceiling value function
double ceil(double x);
float ceilf(float x);
long double ceill(long double x);
These functions shall compute the smallest integral value not less than
An application wishing to check for error situations should set errno
to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these
functions. On return, if errno is non-zero or fetestexcept(FE_INVALID
| FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has
Upon successful completion, ceil(), ceilf(), and ceill() shall return
the smallest integral value not less than x, expressed as a type dou‐
ble, float, or long double, respectively.
If x is NaN, a NaN shall be returned.
If x is ±0 or ±Inf, x shall be returned.
If the correct value would cause overflow, a range error shall occur
and ceil(), ceilf(), and ceill() shall return the value of the macro
HUGE_VAL, HUGE_VALF, and HUGE_VALL, respectively.
These functions shall fail if:
The result overflows.
If the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
then errno shall be set to [ERANGE]. If the integer expression
(math_errhandling & MATH_ERREXCEPT) is non-zero, then the overflow
floating-point exception shall be raised.
The following sections are informative.
The integral value returned by these functions need not be expressible
as an int or long. The return value should be tested before assigning
it to an integer type to avoid the undefined results of an integer
The ceil() function can only overflow when the floating-point represen‐
tation has DBL_MANT_DIG > DBL_MAX_EXP.
On error, the expressions (math_errhandling & MATH_ERRNO) and
(math_errhandling & MATH_ERREXCEPT) are independent of each other, but
at least one of them must be non-zero.
SEE ALSOfeclearexcept(), fetestexcept(), floor(), isnan(), the Base Definitions
volume of IEEE Std 1003.1-2001, Section 4.18, Treatment of Error Condi‐
tions for Mathematical Functions, <math.h>
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 CEIL(3P)