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diff --git a/man/man3/log.3 b/man/man3/log.3 new file mode 100644 index 0000000..29ec350 --- /dev/null +++ b/man/man3/log.3 @@ -0,0 +1,140 @@ +'\" t +.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk) +.\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk +.\" <mtk.manpages@gmail.com> +.\" +.\" SPDX-License-Identifier: Linux-man-pages-copyleft +.\" +.\" References consulted: +.\" Linux libc source code +.\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991) +.\" 386BSD man pages +.\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu) +.\" Modified 1995-08-14 by Arnt Gulbrandsen <agulbra@troll.no> +.\" Modified 2002-07-27 by Walter Harms +.\" (walter.harms@informatik.uni-oldenburg.de) +.\" +.TH log 3 2024-05-02 "Linux man-pages (unreleased)" +.SH NAME +log, logf, logl \- natural logarithmic function +.SH LIBRARY +Math library +.RI ( libm ", " \-lm ) +.SH SYNOPSIS +.nf +.B #include <math.h> +.P +.BI "double log(double " x ); +.BI "float logf(float " x ); +.BI "long double logl(long double " x ); +.fi +.P +.RS -4 +Feature Test Macro Requirements for glibc (see +.BR feature_test_macros (7)): +.RE +.P +.BR logf (), +.BR logl (): +.nf + _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L + || /* Since glibc 2.19: */ _DEFAULT_SOURCE + || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE +.fi +.SH DESCRIPTION +These functions return the natural logarithm of +.IR x . +.SH RETURN VALUE +On success, these functions return the natural logarithm of +.IR x . +.P +If +.I x +is a NaN, +a NaN is returned. +.P +If +.I x +is 1, the result is +0. +.P +If +.I x +is positive infinity, +positive infinity is returned. +.P +If +.I x +is zero, +then a pole error occurs, and the functions return +.RB \- HUGE_VAL , +.RB \- HUGE_VALF , +or +.RB \- HUGE_VALL , +respectively. +.P +If +.I x +is negative (including negative infinity), then +a domain error occurs, and a NaN (not a number) is returned. +.SH ERRORS +See +.BR math_error (7) +for information on how to determine whether an error has occurred +when calling these functions. +.P +The following errors can occur: +.TP +Domain error: \fIx\fP is negative +.I errno +is set to +.BR EDOM . +An invalid floating-point exception +.RB ( FE_INVALID ) +is raised. +.TP +Pole error: \fIx\fP is zero +.I errno +is set to +.BR ERANGE . +A divide-by-zero floating-point exception +.RB ( FE_DIVBYZERO ) +is raised. +.SH ATTRIBUTES +For an explanation of the terms used in this section, see +.BR attributes (7). +.TS +allbox; +lbx lb lb +l l l. +Interface Attribute Value +T{ +.na +.nh +.BR log (), +.BR logf (), +.BR logl () +T} Thread safety MT-Safe +.TE +.SH STANDARDS +C11, POSIX.1-2008. +.SH HISTORY +C99, POSIX.1-2001. +.P +The variant returning +.I double +also conforms to +SVr4, 4.3BSD, C89. +.SH BUGS +In glibc 2.5 and earlier, +taking the +.BR log () +of a NaN produces a bogus invalid floating-point +.RB ( FE_INVALID ) +exception. +.SH SEE ALSO +.BR cbrt (3), +.BR clog (3), +.BR log10 (3), +.BR log1p (3), +.BR log2 (3), +.BR sqrt (3) |