Linux manual pages Section 3: Subroutines  

Name

abs, labs, llabs, imaxabs — compute the absolute value of an integer

Synopsis

#include <stdlib.h>
int abs( int j);
 
long int labs( long int j);
 
long long int llabs( long long int j);
  
#include <inttypes.h>
intmax_t imaxabs( intmax_t j);
 
[Note] Note
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
llabs():
_XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
or cc -std=c99

DESCRIPTION

The abs() function computes the absolute value of the integer argument j. The labs(), llabs() and imaxabs() functions compute the absolute value of the argument j of the appropriate integer type for the function.

RETURN VALUE

Returns the absolute value of the integer argument, of the appropriate integer type for the function.

ATTRIBUTES

Multithreading (see pthreads(7))

The abs(), labs(), llabs(), and imaxabs() functions are thread-safe.

CONFORMING TO

SVr4, POSIX.1-2001, 4.3BSD, C99. C89 only includes the abs() and labs() functions; the functions llabs() and imaxabs() were added in C99.

NOTES

Trying to take the absolute value of the most negative integer is not defined.

The llabs() function is included in glibc since version 2.0, but is not in libc5 or libc4. The imaxabs() function is included in glibc since version 2.1.1.

For llabs() to be declared, it may be necessary to define _ISOC99_SOURCE or _ISOC9X_SOURCE (depending on the version of glibc) before including any standard headers.

GCC handles abs() and labs() as built-in functions. GCC 3.0 also handles llabs() and imaxabs() as built-ins.

SEE ALSO

cabs(3), ceil(3), fabs(3), floor(3), rint(3)

COLOPHON

This page is part of release 3.52 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man−pages/.


  Copyright 1993 David Metcalfe (davidprism.demon.co.uk)

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References consulted:
    Linux libc source code
    Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
    386BSD man pages
Modified Mon Mar 29 22:31:13 1993, David Metcalfe
Modified Sun Jun  6 23:27:50 1993, David Metcalfe
Modified Sat Jul 24 21:45:37 1993, Rik Faith (faithcs.unc.edu)
Modified Sat Dec 16 15:02:59 2000, Joseph S. Myers