]>
Commit | Line | Data |
---|---|---|
fea681da | 1 | .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk) |
3d352631 MK |
2 | .\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk |
3 | .\" <mtk.manpages@gmail.com> | |
fea681da | 4 | .\" |
93015253 | 5 | .\" %%%LICENSE_START(VERBATIM) |
fea681da MK |
6 | .\" Permission is granted to make and distribute verbatim copies of this |
7 | .\" manual provided the copyright notice and this permission notice are | |
8 | .\" preserved on all copies. | |
9 | .\" | |
10 | .\" Permission is granted to copy and distribute modified versions of this | |
11 | .\" manual under the conditions for verbatim copying, provided that the | |
12 | .\" entire resulting derived work is distributed under the terms of a | |
13 | .\" permission notice identical to this one. | |
c13182ef | 14 | .\" |
fea681da MK |
15 | .\" Since the Linux kernel and libraries are constantly changing, this |
16 | .\" manual page may be incorrect or out-of-date. The author(s) assume no | |
17 | .\" responsibility for errors or omissions, or for damages resulting from | |
18 | .\" the use of the information contained herein. The author(s) may not | |
19 | .\" have taken the same level of care in the production of this manual, | |
20 | .\" which is licensed free of charge, as they might when working | |
21 | .\" professionally. | |
c13182ef | 22 | .\" |
fea681da MK |
23 | .\" Formatted or processed versions of this manual, if unaccompanied by |
24 | .\" the source, must acknowledge the copyright and authors of this work. | |
4b72fb64 | 25 | .\" %%%LICENSE_END |
fea681da MK |
26 | .\" |
27 | .\" References consulted: | |
28 | .\" Linux libc source code | |
29 | .\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991) | |
30 | .\" 386BSD man pages | |
31 | .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu) | |
32 | .\" Modified 1995-08-14 by Arnt Gulbrandsen <agulbra@troll.no> | |
33 | .\" Modified 2002-07-27 by Walter Harms | |
34 | .\" (walter.harms@informatik.uni-oldenburg.de) | |
35 | .\" | |
97986708 | 36 | .TH LOG2 3 2016-03-15 "" "Linux Programmer's Manual" |
fea681da MK |
37 | .SH NAME |
38 | log2, log2f, log2l \- base-2 logarithmic function | |
39 | .SH SYNOPSIS | |
40 | .nf | |
41 | .B #include <math.h> | |
68e4db0a | 42 | .PP |
fea681da MK |
43 | .BI "double log2(double " x ); |
44 | .br | |
45 | .BI "float log2f(float " x ); | |
46 | .br | |
47 | .BI "long double log2l(long double " x ); | |
48 | .fi | |
68e4db0a | 49 | .PP |
cc4615cc | 50 | Link with \fI\-lm\fP. |
68e4db0a | 51 | .PP |
cc4615cc MK |
52 | .in -4n |
53 | Feature Test Macro Requirements for glibc (see | |
54 | .BR feature_test_macros (7)): | |
55 | .in | |
68e4db0a | 56 | .PP |
cc4615cc MK |
57 | .ad l |
58 | .BR log2 (), | |
59 | .BR log2f (), | |
60 | .BR log2l (): | |
9fefcdd8 | 61 | .RS 4 |
cd2d5ec1 | 62 | _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L |
9fefcdd8 | 63 | .RE |
cc4615cc | 64 | .ad b |
fea681da | 65 | .SH DESCRIPTION |
5600f73a | 66 | These functions return the base 2 logarithm of |
022671eb | 67 | .IR x . |
3d352631 MK |
68 | .SH RETURN VALUE |
69 | On success, these functions return the base 2 logarithm of | |
70 | .IR x . | |
847e0d88 | 71 | .PP |
3d352631 MK |
72 | For special cases, including where |
73 | .I x | |
74 | is 0, 1, negative, infinity, or NaN, see | |
75 | .BR log (3). | |
fea681da | 76 | .SH ERRORS |
3d352631 MK |
77 | See |
78 | .BR math_error (7) | |
79 | for information on how to determine whether an error has occurred | |
80 | when calling these functions. | |
847e0d88 | 81 | .PP |
3d352631 MK |
82 | For a discussion of the errors that can occur for these functions, see |
83 | .BR log (3). | |
f0d7ce1d MK |
84 | .SH VERSIONS |
85 | These functions first appeared in glibc in version 2.1. | |
b66a6589 MS |
86 | .SH ATTRIBUTES |
87 | For an explanation of the terms used in this section, see | |
88 | .BR attributes (7). | |
89 | .TS | |
90 | allbox; | |
91 | lbw24 lb lb | |
92 | l l l. | |
93 | Interface Attribute Value | |
94 | T{ | |
95 | .BR log2 (), | |
96 | .BR log2f (), | |
97 | .BR log2l () | |
98 | T} Thread safety MT-Safe | |
99 | .TE | |
47297adb | 100 | .SH CONFORMING TO |
9a74e018 | 101 | C99, POSIX.1-2001, POSIX.1-2008. |
847e0d88 | 102 | .PP |
3d352631 MK |
103 | The variant returning |
104 | .I double | |
105 | also conforms to | |
3c78ebef | 106 | SVr4, 4.3BSD. |
47297adb | 107 | .SH SEE ALSO |
fea681da | 108 | .BR cbrt (3), |
36268806 | 109 | .BR clog2 (3), |
be62f421 JE |
110 | .BR log (3), |
111 | .BR log10 (3), | |
fea681da | 112 | .BR sqrt (3) |