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 .sp
  41 .BI "int abs(int " j );
  42 .br
  43 .BI "long int labs(long int " j );
  44 .br
  45 .BI "long long int llabs(long long int " j );
  46 .sp
  47 .B #include <inttypes.h>
  48 .sp
  49 .BI "intmax_t imaxabs(intmax_t " j );
  50 .fi
  51 .sp
  52 .in -4n
  53 Feature Test Macro Requirements for glibc (see
  54 .BR feature_test_macros (7)):
  55 .in
  56 .sp
  57 .ad l
  58 .BR llabs ():
  59 .RS 4
  60 _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
  61 .RE
  62 .ad
  63 .SH DESCRIPTION
  64 The
  65 .BR abs ()
  66 function computes the absolute value of the integer
  67 argument \fIj\fP.
  68 The
  69 .BR labs (),
  70 .BR llabs ()
  71 and
  72 .BR imaxabs ()
  73 functions compute the absolute value of the argument \fIj\fP of the
  74 appropriate integer type for the function.
  75 .SH RETURN VALUE
  76 Returns the absolute value of the integer argument, of the appropriate
  77 integer type for the function.
  78 .SH ATTRIBUTES
  79 For an explanation of the terms used in this section, see
  80 .BR attributes (7).
  81 .ad l
  82 .TS
  83 allbox;
  84 lb lb lb
  85 l l l.
  86 Interface       Attribute       Value
  87 T{
  88 .BR abs (),
  89 .BR labs (),
  90 .BR llabs (),
  91 .BR imaxabs ()
  92 T}      Thread safety   MT-Safe
  93 .TE
  94 .ad
  95 .SH CONFORMING TO
  96 POSIX.1-2001, POSIX.1-2008, C99, SVr4, 4.3BSD.
  97 .\" POSIX.1 (1996 edition) requires only the
  98 .\" .BR abs ()
  99 .\" function.
 100 C89 only
 101 includes the
 102 .BR abs ()
 103 and
 104 .BR labs ()
 105 functions; the functions
 106 .BR llabs ()
 107 and
 108 .BR imaxabs ()
 109 were added in C99.
 110 .SH NOTES
 111 Trying to take the absolute value of the most negative integer
 112 is not defined.
 113 .PP
 114 The
 115 .BR llabs ()
 116 function is included in glibc since version 2.0.
 117 The
 118 .BR imaxabs ()
 119 function is included in
 120 glibc since version 2.1.1.
 121 .PP
 122 For
 123 .BR llabs ()
 124 to be declared, it may be necessary to define
 125 \fB_ISOC99_SOURCE\fP or \fB_ISOC9X_SOURCE\fP (depending on the
 126 version of glibc) before including any standard headers.
 127 .PP
 128 By default,
 129 GCC handles
 130 .BR abs (),
 131 .BR labs (),
 132 and (since GCC 3.0)
 133 .BR llabs ()
 134 and
 135 .BR imaxabs ()
 136 as built-in functions.
 137 .SH SEE ALSO
 138 .BR cabs (3),
 139 .BR ceil (3),
 140 .BR fabs (3),
 141 .BR floor (3),
 142 .BR rint (3)