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
12 log10, log10f, log10l — base 10 logarithm function
13
15 #include <math.h>
16 double log10(double x);
18 float log10f(float x);
19 long double log10l(long double x);
20
22 The functionality described on this reference page is aligned with the
23 ISO C standard. Any conflict between the requirements described here
24 and the ISO C standard is unintentional. This volume of POSIX.1‐2017
25 defers to the ISO C standard.
26 These functions shall compute the base 10 logarithm of their argument
28 x, log10(x).
29 An application wishing to check for error situations should set errno
31 to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these
32 functions. On return, if errno is non-zero or fetestexcept(FE_INVALID |
33 FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has
34 occurred.
35
37 Upon successful completion, these functions shall return the base 10
38 logarithm of x.
39 If x is ±0, a pole error shall occur and log10(), log10f(), and
41 log10l() shall return -HUGE_VAL, -HUGE_VALF, and -HUGE_VALL, respec‐
42 tively.
43 For finite values of x that are less than 0, or if x is -Inf, a domain
45 error shall occur, and either a NaN (if supported), or an implementa‐
46 tion-defined value shall be returned.
47 If x is NaN, a NaN shall be returned.
49 If x is 1, +0 shall be returned.
51 If x is +Inf, +Inf shall be returned.
53
55 These functions shall fail if:
56 Domain Error
58 The finite value of x is negative, or x is -Inf.
59 If the integer expression (math_errhandling & MATH_ERRNO)
61 is non-zero, then errno shall be set to [EDOM]. If the
62 integer expression (math_errhandling & MATH_ERREXCEPT) is
63 non-zero, then the invalid floating-point exception shall
64 be raised.
65 Pole Error The value of x is zero.
67 If the integer expression (math_errhandling & MATH_ERRNO)
69 is non-zero, then errno shall be set to [ERANGE]. If the
70 integer expression (math_errhandling & MATH_ERREXCEPT) is
71 non-zero, then the divide-by-zero floating-point exception
72 shall be raised.
73 The following sections are informative.
75
77 None.
78
80 On error, the expressions (math_errhandling & MATH_ERRNO) and
81 (math_errhandling & MATH_ERREXCEPT) are independent of each other, but
82 at least one of them must be non-zero.
83
85 None.
86
88 None.
89
91 feclearexcept(), fetestexcept(), isnan(), log(), pow()
92 The Base Definitions volume of POSIX.1‐2017, Section 4.20, Treatment of
94 Error Conditions for Mathematical Functions, <math.h>
95
97 Portions of this text are reprinted and reproduced in electronic form
98 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
99 table Operating System Interface (POSIX), The Open Group Base Specifi‐
100 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
101 Electrical and Electronics Engineers, Inc and The Open Group. In the
102 event of any discrepancy between this version and the original IEEE and
103 The Open Group Standard, the original IEEE and The Open Group Standard
104 is the referee document. The original Standard can be obtained online
105 at http://www.opengroup.org/unix/online.html .
106 Any typographical or formatting errors that appear in this page are
108 most likely to have been introduced during the conversion of the source
109 files to man page format. To report such errors, see https://www.ker‐
110 nel.org/doc/man-pages/reporting_bugs.html .
111IEEE/The Open Group 2017 LOG10(3P)