stdlib/bsearch.3

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  36 .\"     @(#)bsearch.3   8.3 (Berkeley) 4/19/94
  37 .\" $FreeBSD: src/lib/libc/stdlib/bsearch.3,v 1.8 2001/09/07 14:46:35 asmodai Exp $
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  39 .Dd May 20, 2008
  40 .Dt BSEARCH 3
  41 .Os
  42 .Sh NAME
  43 #ifdef UNIFDEF_BLOCKS
  44 .Nm bsearch ,
  45 .Nm bsearch_b
  46 #else
  47 .Nm bsearch
  48 #endif
  49 .Nd binary search of a sorted table
  50 .Sh SYNOPSIS
  51 .In stdlib.h
  52 .Ft void *
  53 .Fn bsearch "const void *key" "const void *base" "size_t nel" "size_t width" "int (*compar) (const void *, const void *)"
  54 #ifdef UNIFDEF_BLOCKS
  55 .Ft void *
  56 .Fn bsearch_b "const void *key" "const void *base" "size_t nel" "size_t width" "int (^compar) (const void *, const void *)"
  57 #endif
  58 .Sh DESCRIPTION
  59 The
  60 .Fn bsearch
  61 function searches an array of
  62 .Fa nel
  63 objects, the initial member of which is
  64 pointed to by
  65 .Fa base ,
  66 for a member that matches the object pointed to by
  67 .Fa key .
  68 The size (in bytes) of each member of the array is specified by
  69 .Fa width .
  70 .Pp
  71 The contents of the array should be in ascending sorted order according
  72 to the comparison function referenced by
  73 .Fa compar .
  74 The
  75 .Fa compar
  76 routine
  77 is expected to have
  78 two arguments which point to the
  79 .Fa key
  80 object and to an array member, in that order.
  81 It should return an integer which is
  82 less than, equal to, or greater than zero if the
  83 .Fa key
  84 object is found, respectively, to be less than, to match, or be
  85 greater than the array member.
  86 #ifdef UNIFDEF_BLOCKS
  87 .Pp
  88 The
  89 .Fn bsearch_b
  90 function is like
  91 .Fn bsearch
  92 except the callback
  93 .Fa compar
  94 is a block pointer instead of a function pointer.
  95 #endif
  96 .Sh RETURN VALUES
  97 The
  98 .Fn bsearch
  99 #ifdef UNIFDEF_BLOCKS
 100 and
 101 .Fn bsearch_b
 102 functions
 103 #else
 104 function
 105 #endif
 106 returns a pointer to a matching member of the array, or a null
 107 pointer if no match is found.
 108 If two members compare as equal, which member is matched is unspecified.
 109 .Sh SEE ALSO
 110 .Xr db 3 ,
 111 .Xr lsearch 3 ,
 112 .Xr qsort 3
 113 .\" .Xr tsearch 3
 114 .Sh STANDARDS
 115 The
 116 .Fn bsearch
 117 function conforms to
 118 .St -isoC .