ceill(3) - f38

1ceil(3)                    Library Functions Manual                    ceil(3)
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NAME

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

10       Math library (libm, -lm)
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SYNOPSIS

13       #include <math.h>
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15       double ceil(double x);
16       float ceilf(float x);
17       long double ceill(long double x);
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19   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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21       ceilf(), ceill():
22           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
23               || /* Since glibc 2.19: */ _DEFAULT_SOURCE
24               || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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DESCRIPTION

27       These functions return the smallest integral value  that  is  not  less
28       than x.
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30       For example, ceil(0.5) is 1.0, and ceil(-0.5) is 0.0.
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RETURN VALUE

33       These functions return the ceiling of x.
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35       If x is integral, +0, -0, NaN, or infinite, x itself is returned.
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ERRORS

38       No  errors  occur.  POSIX.1-2001 documents a range error for overflows,
39       but see NOTES.
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ATTRIBUTES

42       For an  explanation  of  the  terms  used  in  this  section,  see  at‐
43       tributes(7).
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45       ┌────────────────────────────────────────────┬───────────────┬─────────┐
46       │Interface                                   │ Attribute     │ Value   │
47       ├────────────────────────────────────────────┼───────────────┼─────────┤
48       │ceil(), ceilf(), ceill()                    │ Thread safety │ MT-Safe │
49       └────────────────────────────────────────────┴───────────────┴─────────┘
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STANDARDS

52       C11, POSIX.1-2008.
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HISTORY

55       C99, POSIX.1-2001.
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57       The variant returning double also conforms to SVr4, 4.3BSD, C89.
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NOTES

60       SUSv2 and POSIX.1-2001 contain text about overflow (which might set er‐
61       rno to ERANGE, or raise an FE_OVERFLOW exception).   In  practice,  the
62       result  cannot  overflow on any current machine, so this error-handling
63       stuff is just nonsense.  (More precisely, overflow can happen only when
64       the maximum value of the exponent is smaller than the number of mantis‐
65       sa bits.  For the IEEE-754 standard 32-bit  and  64-bit  floating-point
66       numbers  the maximum value of the exponent is 127 (respectively, 1023),
67       and the number of mantissa bits including the implicit bit is  24  (re‐
68       spectively, 53).)
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70       The  integral  value  returned  by  these functions may be too large to
71       store in an integer type (int, long,  etc.).   To  avoid  an  overflow,
72       which  will  produce undefined results, an application should perform a
73       range check on the returned value before assigning  it  to  an  integer
74       type.
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