{"id":5597,"date":"2022-12-20T18:45:34","date_gmt":"2022-12-20T21:45:34","guid":{"rendered":"http:\/\/lode.uno\/linux-man\/index.php\/2022\/12\/20\/logb-man3p\/"},"modified":"2022-12-20T18:45:34","modified_gmt":"2022-12-20T21:45:34","slug":"logb-man3p","status":"publish","type":"post","link":"https:\/\/lode.uno\/linux-man\/2022\/12\/20\/logb-man3p\/","title":{"rendered":"LOGB (man3p)"},"content":{"rendered":"

LOGB<\/h1>\n

PROLOG<\/a>
NAME<\/a>
SYNOPSIS<\/a>
DESCRIPTION<\/a>
RETURN VALUE<\/a>
ERRORS<\/a>
EXAMPLES<\/a>
APPLICATION USAGE<\/a>
RATIONALE<\/a>
FUTURE DIRECTIONS<\/a>
SEE ALSO<\/a>
COPYRIGHT<\/a> <\/p>\n

\n

PROLOG <\/a> <\/h2>\n

This manual page is part of the POSIX Programmer\u2019s Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.<\/p>\n

NAME <\/a> <\/h2>\n

logb, logbf, logbl \u2014 radix-independent exponent<\/p>\n

SYNOPSIS <\/a> <\/h2>\n

#include <\/p>\n

double logb(double x<\/i>);
float logbf(float x<\/i>);
long double logbl(long double x<\/i>);<\/p>\n

DESCRIPTION <\/a> <\/h2>\n

The functionality described on this reference page is aligned with the ISO\u00a0C standard. Any conflict between the requirements described here and the ISO\u00a0C standard is unintentional. This volume of POSIX.1-2017 defers to the ISO\u00a0C standard.<\/p>\n

These functions shall compute the exponent of x<\/i>, which is the integral part of log r<\/small><\/small><\/i> |x<\/i>|, as a signed floating-point value, for non-zero x<\/i>, where r<\/i> is the radix of the machine\u2019s floating-point arithmetic, which is the value of FLT_RADIX defined in the <\/i> header.<\/p>\n

If x<\/i> is subnormal it is treated as though it were normalized; thus for finite positive x<\/i>:<\/p>\n

1 <= x<\/i> bodies manpages.csv script_extrae_body.sh script.sh usr FLT_RADIX -logb(x)<\/small><\/small> < FLT_RADIX<\/p>\n

An application wishing to check for error situations should set errno<\/i> to zero and call feclearexcept<\/i>(FE_ALL_EXCEPT) before calling these functions. On return, if errno<\/i> is non-zero or fetestexcept<\/i>(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred.<\/p>\n

RETURN VALUE <\/a> <\/h2>\n

Upon successful completion, these functions shall return the exponent of x<\/i>.<\/p>\n

If x<\/i> is \u00b10, logb<\/i>(), logbf<\/i>(), and logbl<\/i>() shall return \u2212HUGE_VAL, \u2212HUGE_VALF, and \u2212HUGE_VALL, respectively.<\/p>\n

On systems that support the IEC 60559 Floating-Point option, a pole error shall occur;
otherwise, a pole error may occur.<\/p>\n

If x<\/i> is NaN, a NaN shall be returned.<\/p>\n

If x<\/i> is \u00b1Inf, +Inf shall be returned.<\/p>\n

ERRORS <\/a> <\/h2>\n

These functions shall fail if:<\/p>\n\n\n
<\/td>\n\n

Pole\u00a0Error<\/p>\n<\/td>\n

<\/td>\n\n

The value of x<\/i> is \u00b10.<\/p>\n<\/td>\n

 <\/td>\n<\/tr>\n<\/table>\n

If the integer expression (math_errhandling<\/i> & MATH_ERRNO) is non-zero, then errno<\/i> shall be set to [ERANGE]<\/b>. If the integer expression (math_errhandling<\/i> & MATH_ERREXCEPT) is non-zero, then the divide-by-zero floating-point exception shall be raised.<\/p>\n

These functions may fail if:<\/p>\n\n\n
<\/td>\n\n

Pole\u00a0Error<\/p>\n<\/td>\n

<\/td>\n\n

The value of x<\/i> is 0.<\/p>\n<\/td>\n

 <\/td>\n<\/tr>\n<\/table>\n

If the integer expression (math_errhandling<\/i> & MATH_ERRNO) is non-zero, then errno<\/i> shall be set to [ERANGE]<\/b>. If the integer expression (math_errhandling<\/i> & MATH_ERREXCEPT) is non-zero, then the divide-by-zero floating-point exception shall be raised.<\/p>\n

The following sections are informative.<\/i><\/p>\n

EXAMPLES <\/a> <\/h2>\n

None.<\/p>\n

APPLICATION USAGE <\/a> <\/h2>\n

On error, the expressions (math_errhandling<\/i> & MATH_ERRNO) and (math_errhandling<\/i> & MATH_ERREXCEPT) are independent of each other, but at least one of them must be non-zero.<\/p>\n

RATIONALE <\/a> <\/h2>\n

None.<\/p>\n

FUTURE DIRECTIONS <\/a> <\/h2>\n

None.<\/p>\n

SEE ALSO <\/a> <\/h2>\n

feclearexcept<\/i>(), fetestexcept<\/i>(), ilogb<\/i>(), scalbln<\/i>()<\/p>\n

The Base Definitions volume of POSIX.1-2017, Section 4.20<\/i>, Treatment of Error Conditions for Mathematical Functions<\/i>, <\/b>, <\/b><\/p>\n

COPYRIGHT <\/a> <\/h2>\n

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology — Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http:\/\/www.opengroup.org\/unix\/online.html .<\/p>\n

Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https:\/\/www.kernel.org\/doc\/man-pages\/reporting_bugs.html .<\/p>\n

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