1LOG10(3P) POSIX Programmer's Manual LOG10(3P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
13 log10, log10f, log10l — base 10 logarithm function
14
16 #include <math.h>
17 double log10(double x);
19 float log10f(float x);
20 long double log10l(long double x);
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23 The functionality described on this reference page is aligned with the
24 ISO C standard. Any conflict between the requirements described here
25 and the ISO C standard is unintentional. This volume of POSIX.1‐2008
26 defers to the ISO C standard.
27 These functions shall compute the base 10 logarithm of their argument
29 x, log10(x).
30 An application wishing to check for error situations should set errno
32 to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these
33 functions. On return, if errno is non-zero or fetestexcept(FE_INVALID |
34 FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has
35 occurred.
36
38 Upon successful completion, these functions shall return the base 10
39 logarithm of x.
40 If x is ±0, a pole error shall occur and log10(), log10f(), and
42 log10l() shall return −HUGE_VAL, −HUGE_VALF, and −HUGE_VALL, respec‐
43 tively.
44 For finite values of x that are less than 0, or if x is −Inf, a domain
46 error shall occur, and either a NaN (if supported), or an implementa‐
47 tion-defined value shall be returned.
48 If x is NaN, a NaN shall be returned.
50 If x is 1, +0 shall be returned.
52 If x is +Inf, +Inf shall be returned.
54
56 These functions shall fail if:
57 Domain Error
59 The finite value of x is negative, or x is −Inf.
60 If the integer expression (math_errhandling & MATH_ERRNO)
62 is non-zero, then errno shall be set to [EDOM]. If the
63 integer expression (math_errhandling & MATH_ERREXCEPT) is
64 non-zero, then the invalid floating-point exception shall
65 be raised.
66 Pole Error The value of x is zero.
68 If the integer expression (math_errhandling & MATH_ERRNO)
70 is non-zero, then errno shall be set to [ERANGE]. If the
71 integer expression (math_errhandling & MATH_ERREXCEPT) is
72 non-zero, then the divide-by-zero floating-point exception
73 shall be raised.
74 The following sections are informative.
76
78 None.
79
81 On error, the expressions (math_errhandling & MATH_ERRNO) and
82 (math_errhandling & MATH_ERREXCEPT) are independent of each other, but
83 at least one of them must be non-zero.
84
86 None.
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89 None.
90
92 feclearexcept(), fetestexcept(), isnan(), log(), pow()
93 The Base Definitions volume of POSIX.1‐2008, Section 4.19, Treatment of
95 Error Conditions for Mathematical Functions, <math.h>
96
98 Portions of this text are reprinted and reproduced in electronic form
99 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
100 -- Portable Operating System Interface (POSIX), The Open Group Base
101 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
102 cal and Electronics Engineers, Inc and The Open Group. (This is
103 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
104 event of any discrepancy between this version and the original IEEE and
105 The Open Group Standard, the original IEEE and The Open Group Standard
106 is the referee document. The original Standard can be obtained online
107 at http://www.unix.org/online.html .
108 Any typographical or formatting errors that appear in this page are
110 most likely to have been introduced during the conversion of the source
111 files to man page format. To report such errors, see https://www.ker‐
112 nel.org/doc/man-pages/reporting_bugs.html .
113IEEE/The Open Group 2013 LOG10(3P)