man3/abs.3

   1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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  23 .\" References consulted:
  24 .\"     Linux libc source code
  25 .\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
  26 .\"     386BSD man pages
  27 .\" Modified Mon Mar 29 22:31:13 1993, David Metcalfe
  28 .\" Modified Sun Jun  6 23:27:50 1993, David Metcalfe
  29 .\" Modified Sat Jul 24 21:45:37 1993, Rik Faith (faith@cs.unc.edu)
  30 .\" Modified Sat Dec 16 15:02:59 2000, Joseph S. Myers
  31 .\"
  32 .TH ABS 3  2000-12-17 "GNU" "Linux Programmer's Manual"
  33 .SH NAME
  34 abs, labs, llabs, imaxabs \- compute the absolute value of an integer
  35 .SH SYNOPSIS
  36 .nf
  37 .B #include <stdlib.h>
  38 .sp
  39 .BI "int abs(int " j );
  40 .br
  41 .BI "long int labs(long int " j );
  42 .br
  43 .BI "long long int llabs(long long int " j );
  44 .sp
  45 .B #include <inttypes.h>
  46 .sp
  47 .BI "intmax_t imaxabs(intmax_t " j );
  48 .fi
  49 .SH DESCRIPTION
  50 The \fBabs\fP() function computes the absolute value of the integer
  51 argument \fIj\fP.
  52 The \fBlabs\fP(), \fBllabs\fP() and \fBimaxabs\fP()
  53 functions compute the absolute value of the argument \fIj\fP of the
  54 appropriate integer type for the function.
  55 .SH "RETURN VALUE"
  56 Returns the absolute value of the integer argument, of the appropriate
  57 integer type for the function.
  58 .SH "CONFORMING TO"
  59 SVr4, POSIX.1-2001, 4.3BSD, C99.
  60 .\" POSIX.1 (1996 edition) only requires the \fBabs\fP() function.
  61 C89 only
  62 includes the \fBabs\fP() and \fBlabs\fP() functions; the functions
  63 \fBllabs\fP() and \fBimaxabs\fP() were added in C99.
  64 .SH NOTES
  65 Trying to take the absolute value of the most negative integer
  66 is not defined.
  67 .PP
  68 The \fBllabs\fP() function is included in glibc since version 2.0, but
  69 is not in libc5 or libc4.
  70 The \fBimaxabs\fP() function is included in
  71 glibc since version 2.1.1.
  72 .PP
  73 For \fBllabs\fP() to be declared, it may be necessary to define
  74 \fB_ISOC99_SOURCE\fP or \fB_ISOC9X_SOURCE\fP (depending on the
  75 version of glibc) before including any standard headers.
  76 .PP
  77 GCC handles \fBabs\fP() and \fBlabs\fP() as builtin functions.
  78 GCC 3.0 also handles \fBllabs\fP() and \fBimaxabs\fP() as builtins.
  79 .SH "SEE ALSO"
  80 .BR cabs (3),
  81 .BR ceil (3),
  82 .BR fabs (3),
  83 .BR floor (3),
  84 .BR rint (3)