man3/abs.3

   1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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  25 .\" References consulted:
  26 .\"     Linux libc source code
  27 .\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
  28 .\"     386BSD man pages
  29 .\" Modified Mon Mar 29 22:31:13 1993, David Metcalfe
  30 .\" Modified Sun Jun  6 23:27:50 1993, David Metcalfe
  31 .\" Modified Sat Jul 24 21:45:37 1993, Rik Faith (faith@cs.unc.edu)
  32 .\" Modified Sat Dec 16 15:02:59 2000, Joseph S. Myers
  33 .\"
  34 .TH ABS 3  2016-03-15 "GNU" "Linux Programmer's Manual"
  35 .SH NAME
  36 abs, labs, llabs, imaxabs \- compute the absolute value of an integer
  37 .SH SYNOPSIS
  38 .nf
  39 .B #include <stdlib.h>
  40 .PP
  41 .BI "int abs(int " j );
  42 .BI "long int labs(long int " j );
  43 .BI "long long int llabs(long long int " j );
  44
  45 .B #include <inttypes.h>
  46 .PP
  47 .BI "intmax_t imaxabs(intmax_t " j );
  48 .fi
  49 .PP
  50 .in -4n
  51 Feature Test Macro Requirements for glibc (see
  52 .BR feature_test_macros (7)):
  53 .in
  54 .PP
  55 .ad l
  56 .BR llabs ():
  57 .RS 4
  58 _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
  59 .RE
  60 .ad
  61 .SH DESCRIPTION
  62 The
  63 .BR abs ()
  64 function computes the absolute value of the integer
  65 argument \fIj\fP.
  66 The
  67 .BR labs (),
  68 .BR llabs ()
  69 and
  70 .BR imaxabs ()
  71 functions compute the absolute value of the argument \fIj\fP of the
  72 appropriate integer type for the function.
  73 .SH RETURN VALUE
  74 Returns the absolute value of the integer argument, of the appropriate
  75 integer type for the function.
  76 .SH ATTRIBUTES
  77 For an explanation of the terms used in this section, see
  78 .BR attributes (7).
  79 .ad l
  80 .TS
  81 allbox;
  82 lb lb lb
  83 l l l.
  84 Interface       Attribute       Value
  85 T{
  86 .BR abs (),
  87 .BR labs (),
  88 .BR llabs (),
  89 .BR imaxabs ()
  90 T}      Thread safety   MT-Safe
  91 .TE
  92 .ad
  93 .SH CONFORMING TO
  94 POSIX.1-2001, POSIX.1-2008, C99, SVr4, 4.3BSD.
  95 .\" POSIX.1 (1996 edition) requires only the
  96 .\" .BR abs ()
  97 .\" function.
  98 C89 only
  99 includes the
 100 .BR abs ()
 101 and
 102 .BR labs ()
 103 functions; the functions
 104 .BR llabs ()
 105 and
 106 .BR imaxabs ()
 107 were added in C99.
 108 .SH NOTES
 109 Trying to take the absolute value of the most negative integer
 110 is not defined.
 111 .PP
 112 The
 113 .BR llabs ()
 114 function is included in glibc since version 2.0.
 115 The
 116 .BR imaxabs ()
 117 function is included in
 118 glibc since version 2.1.1.
 119 .PP
 120 For
 121 .BR llabs ()
 122 to be declared, it may be necessary to define
 123 \fB_ISOC99_SOURCE\fP or \fB_ISOC9X_SOURCE\fP (depending on the
 124 version of glibc) before including any standard headers.
 125 .PP
 126 By default,
 127 GCC handles
 128 .BR abs (),
 129 .BR labs (),
 130 and (since GCC 3.0)
 131 .BR llabs ()
 132 and
 133 .BR imaxabs ()
 134 as built-in functions.
 135 .SH SEE ALSO
 136 .BR cabs (3),
 137 .BR ceil (3),
 138 .BR fabs (3),
 139 .BR floor (3),
 140 .BR rint (3)