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2 .\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
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27 .\" Inspired by a page by Walter Harms created 2002-08-10
29 .TH ILOGB 3 2017-09-15 "" "Linux Programmer's Manual"
31 ilogb, ilogbf, ilogbl \- get integer exponent of a floating-point value
35 .BI "int ilogb(double " x );
37 .BI "int ilogbf(float " x );
39 .BI "int ilogbl(long double " x );
44 Feature Test Macro Requirements for glibc (see
45 .BR feature_test_macros (7)):
51 _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
52 || _XOPEN_SOURCE\ >=\ 500
53 .\" || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
54 || /* Since glibc 2.19: */ _DEFAULT_SOURCE
55 || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
61 _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
62 || /* Since glibc 2.19: */ _DEFAULT_SOURCE
63 || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
67 These functions return the exponent part of their argument
69 When no error occurs, these functions
70 are equivalent to the corresponding
75 On success, these functions return the exponent of
81 is zero, then a domain error occurs, and the functions return
82 .\" the POSIX.1 spec for logb() says logb() gives pole error for this
83 .\" case, but for ilogb() it says domain error.
85 .\" glibc: The numeric value is either `INT_MIN' or `-INT_MAX'.
89 is a NaN, then a domain error occurs, and the functions return
91 .\" glibc: The numeric value is either `INT_MIN' or `INT_MAX'.
92 .\" On i386, FP_ILOGB0 and FP_ILOGBNAN have the same value.
96 is negative infinity or positive infinity, then
97 a domain error occurs, and the functions return
100 .\" POSIX.1-2001 also says:
101 .\" If the correct value is greater than {INT_MAX}, {INT_MAX}
102 .\" shall be returned and a domain error shall occur.
104 .\" If the correct value is less than {INT_MIN}, {INT_MIN}
105 .\" shall be returned and a domain error shall occur.
109 for information on how to determine whether an error has occurred
110 when calling these functions.
112 The following errors can occur:
114 Domain error: \fIx\fP is 0 or a NaN
115 An invalid floating-point exception
124 Domain error: \fIx\fP is an infinity
125 An invalid floating-point exception
133 For an explanation of the terms used in this section, see
139 Interface Attribute Value
144 T} Thread safety MT-Safe
147 C99, POSIX.1-2001, POSIX.1-2008.
149 .\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6794
150 Before version 2.16, the following bugs existed in the
151 glibc implementation of these functions:
153 The domain error case where
155 is 0 or a NaN did not cause
157 to be set or (on some architectures) raise a floating-point exception.
159 The domain error case where
161 is an infinity did not cause
163 to be set or raise a floating-point exception.