NAME
log, logf, logl - natural logarithmic function
SYNOPSIS
#include <math.h>
double log(double x);
float logf(float x);
long double logl(long double x);
Link with -lm.
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
logf(), logl():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
DESCRIPTION
These functions return the natural logarithm of x.
RETURN VALUE
On success, these functions return the natural logarithm of x. If x is a NaN, a NaN is returned. If x is 1, the result is +0. If x is positive infinity, positive infinity is returned. If x is zero, then a pole error occurs, and the functions return -HUGE_VAL, -HUGE_VALF, or -HUGE_VALL, respectively. If x is negative (including negative infinity), then a domain error occurs, and a NaN (not a number) is returned.
ERRORS
See math_error(7) for information on how to determine whether an error
has occurred when calling these functions.
The following errors can occur:
Domain error: x is negative
errno is set to EDOM. An invalid floating-point exception
(FE_INVALID) is raised.
Pole error: x is zero
errno is set to ERANGE. A divide-by-zero floating-point
exception (FE_DIVBYZERO) is raised.
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7). Interface Attribute Value log(), logf(), logl() Thread safety MT-Safe
CONFORMING TO
C99, POSIX.1-2001, POSIX.1-2008. The variant returning double also conforms to SVr4, 4.3BSD, C89.
BUGS
In glibc 2.5 and earlier, taking the log() of a NaN produces a bogus invalid floating-point (FE_INVALID) exception.
SEE ALSO
cbrt(3), clog(3), log10(3), log1p(3), log2(3), sqrt(3)
COLOPHON
This page is part of release 4.09 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
2016-03-15 LOG(3)
More Linux Commands
manpages/twm.1.html
twm(1) - Tab Window Manager for the X Window System.........
Twm is a window manager for the X Window System. It provides titlebars, shaped windows, several forms of icon management, user-defined macro functions, click-to
manpages/XGetWMSizeHints.3.html
XGetWMSizeHints(3) - allocate size hints structure and set o
The XAllocSizeHints function allocates and returns a pointer to a XSizeHints structure. Note that all fields in the XSizeHints structure are initially set to ze
manpages/ffcfstress.1.html
ffcfstress(1) constant force stress test for force-feedback
ffcfstress stress tests constant non-enveloped forces on a force feedback device. It simulates a moving spring force by applying a frequently updated constant f
manpages/msgconv.1.html
msgconv(1) - character set conversion for message catalog...
Converts a translation catalog to a different character encoding. Mandatory arguments to long options are mandatory for short options too. Input file location:
manpages/wctype.3.html
wctype(3) - wide-character classification - Linux man page
The wctype_t type represents a property which a wide character may or may not have. In other words, it represents a class of wide characters. This types nature
manpages/snmptranslate.1.html
snmptranslate(1) - translate MIB OID names between numeric a
snmptranslate is an application that translates one or more SNMP object identifier values from their symbolic (textual) forms into their numerical forms (or vic
manpages/add_key.2.html
add_key(2) - Add a key to the kernel's key management facili
add_key() asks the kernel to create or update a key of the given type and description, instantiate it with the payload of length plen, and to attach it to the n
manpages/funzip.1.html
funzip(1) - filter for extracting from a ZIP archive in a pi
funzip without a file argument acts as a filter; that is, it assumes that a ZIP archive (or a gzipdaemon(3) file) is being piped into standard input, and it ext
manpages/pamtopfm.1.html
pamtopfm(1) - Convert Netpbm image to PFM (Portable Float Ma
This program is part of Netpbm(1) pamtopfm reads a Netpbm image (PNM or PAM) and converts it to a PFM (Portable Float Map) image. The PFM (Portable Float Map) i
manpages/waddstr.3ncurses.html
mvwaddstr(3ncurses) - add a string of characters to a curses
These functions write the (null-terminated) character string str on the given window. It is similar to calling waddch once for each character in the string. The
manpages/regshell.1.html
regshell(1) Windows registry file browser using readline....
regshell is a utility that lets you browse thru a Windows registry file as if you were using a regular unix shell to browse thru a file system. OPTIONS --help S
manpages/mvwinchstr.3ncurses.html
mvwinchstr(3ncurses) - get a string of characters (and attri
These routines return a NULL-terminated array of chtype quantities, starting at the current cursor position in the named window and ending at the right margin o
