CEIL(P) POSIX Programmer's Manual CEIL(P)
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 x.
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 occurred.
Upon successful completion, ceil(), ceilf(), and ceill() shall return the smallest inte-
gral value not less than x, expressed as a type double, float, or long double, respec-
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,
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 overflow.
The ceil() function can only overflow when the floating-point representation 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.
feclearexcept() , fetestexcept() , floor() , isnan() , the Base Definitions volume of
IEEE Std 1003.1-2001, Section 4.18, Treatment of Error Conditions for Mathematical Func-
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 orig-
inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 CEIL(P)