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  2015-08-08 "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 .br
  62 or
  63 .I cc\ -std=c99
  64 .RE
  65 .ad
  66 .SH DESCRIPTION
  67 The
  68 .BR abs ()
  69 function computes the absolute value of the integer
  70 argument \fIj\fP.
  71 The
  72 .BR labs (),
  73 .BR llabs ()
  74 and
  75 .BR imaxabs ()
  76 functions compute the absolute value of the argument \fIj\fP of the
  77 appropriate integer type for the function.
  78 .SH RETURN VALUE
  79 Returns the absolute value of the integer argument, of the appropriate
  80 integer type for the function.
  81 .SH ATTRIBUTES
  82 For an explanation of the terms used in this section, see
  83 .BR attributes (7).
  84 .ad l
  85 .TS
  86 allbox;
  87 lb lb lb
  88 l l l.
  89 Interface       Attribute       Value
  90 T{
  91 .BR abs (),
  92 .BR labs (),
  93 .BR llabs (),
  94 .BR imaxabs ()
  95 T}      Thread safety   MT-Safe
  96 .TE
  97 .ad
  98 .SH CONFORMING TO
  99 POSIX.1-2001, POSIX.1-2008, C99, SVr4, 4.3BSD.
 100 .\" POSIX.1 (1996 edition) requires only the
 101 .\" .BR abs ()
 102 .\" function.
 103 C89 only
 104 includes the
 105 .BR abs ()
 106 and
 107 .BR labs ()
 108 functions; the functions
 109 .BR llabs ()
 110 and
 111 .BR imaxabs ()
 112 were added in C99.
 113 .SH NOTES
 114 Trying to take the absolute value of the most negative integer
 115 is not defined.
 116 .PP
 117 The
 118 .BR llabs ()
 119 function is included in glibc since version 2.0.
 120 The
 121 .BR imaxabs ()
 122 function is included in
 123 glibc since version 2.1.1.
 124 .PP
 125 For
 126 .BR llabs ()
 127 to be declared, it may be necessary to define
 128 \fB_ISOC99_SOURCE\fP or \fB_ISOC9X_SOURCE\fP (depending on the
 129 version of glibc) before including any standard headers.
 130 .PP
 131 By default,
 132 GCC handles
 133 .BR abs (),
 134 .BR labs (),
 135 and (since GCC 3.0)
 136 .BR llabs ()
 137 and
 138 .BR imaxabs ()
 139 as built-in functions.
 140 .SH SEE ALSO
 141 .BR cabs (3),
 142 .BR ceil (3),
 143 .BR fabs (3),
 144 .BR floor (3),
 145 .BR rint (3)