1CEIL(3) Linux Programmer's Manual CEIL(3)
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6 ceil, ceilf, ceill - ceiling function: smallest integral value not less
7 than argument
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10 #include <math.h>
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12 double ceil(double x);
13 float ceilf(float x);
14 long double ceill(long double x);
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16 Link with -lm.
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18 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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20 ceilf(), ceill():
21 _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
22 || /* Since glibc 2.19: */ _DEFAULT_SOURCE
23 || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
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26 These functions return the smallest integral value that is not less
27 than x.
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29 For example, ceil(0.5) is 1.0, and ceil(-0.5) is 0.0.
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32 These functions return the ceiling of x.
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34 If x is integral, +0, -0, NaN, or infinite, x itself is returned.
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37 No errors occur. POSIX.1-2001 documents a range error for overflows,
38 but see NOTES.
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41 For an explanation of the terms used in this section, see
42 attributes(7).
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44 ┌─────────────────────────┬───────────────┬─────────┐
45 │Interface │ Attribute │ Value │
46 ├─────────────────────────┼───────────────┼─────────┤
47 │ceil(), ceilf(), ceill() │ Thread safety │ MT-Safe │
48 └─────────────────────────┴───────────────┴─────────┘
50 C99, POSIX.1-2001, POSIX.1-2008.
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52 The variant returning double also conforms to SVr4, 4.3BSD, C89.
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55 SUSv2 and POSIX.1-2001 contain text about overflow (which might set
56 errno to ERANGE, or raise an FE_OVERFLOW exception). In practice, the
57 result cannot overflow on any current machine, so this error-handling
58 stuff is just nonsense. (More precisely, overflow can happen only when
59 the maximum value of the exponent is smaller than the number of man‐
60 tissa bits. For the IEEE-754 standard 32-bit and 64-bit floating-point
61 numbers the maximum value of the exponent is 128 (respectively, 1024),
62 and the number of mantissa bits is 24 (respectively, 53).)
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64 The integral value returned by these functions may be too large to
65 store in an integer type (int, long, etc.). To avoid an overflow,
66 which will produce undefined results, an application should perform a
67 range check on the returned value before assigning it to an integer
68 type.
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71 floor(3), lrint(3), nearbyint(3), rint(3), round(3), trunc(3)
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74 This page is part of release 5.04 of the Linux man-pages project. A
75 description of the project, information about reporting bugs, and the
76 latest version of this page, can be found at
77 https://www.kernel.org/doc/man-pages/.
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81 2017-09-15 CEIL(3)