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BSEARCH(3)		    Library Functions Manual		    BSEARCH(3)

NAME
       bsearch -- binary search	of a sorted table

LIBRARY
       Standard	C Library (libc, -lc)

SYNOPSIS
       #include	<stdlib.h>

       void *
       bsearch(const  void  *key, const	void *base, size_t nmemb, size_t size,
	   int (*compar) (const	void *,	const void *));

DESCRIPTION
       The bsearch() function searches an array	of nmemb objects, the  initial
       member  of  which  is pointed to	by base, for a member that matches the
       object pointed to by key.  The size of each  member  of	the  array  is
       specified by size.

       The contents of the array should	be in ascending	sorted order according
       to the comparison function referenced by	compar.	 The compar routine is
       expected	 to have two arguments which point to the key object and to an
       array member, in	that order, and	should return an  integer  less	 than,
       equal  to,  or  greater	than  zero if the key object is	found, respec-
       tively, to be less than,	to match, or be	greater	than the array member.
       See the int_compare sample function in qsort(3) for a comparison	 func-
       tion that is also compatible with bsearch().

RETURN VALUES
       The  bsearch()  function	 returns a pointer to a	matching member	of the
       array, or a null	pointer	if no match is found.  If two members  compare
       as equal, which member is matched is unspecified.

EXAMPLES
       A sample	program	that searches people by	age in a sorted	array:

       #include	<assert.h>
       #include	<stdint.h>
       #include	<stdio.h>
       #include	<stdlib.h>
       #include	<string.h>

       struct person {
	       const char      *name;
	       int	       age;
       };

       static int
       compare(const void *a, const void *b)
       {
	       const int *age;
	       const struct person *person;

	       age = a;
	       person =	b;

	       return (*age - person->age);
       }

       int
       main(void)
       {
	       struct person *friend;
	       int age;
	       /* Sorted array */
	       const struct person friends[] = {
		       { "paul", 22 },
		       { "anne", 25 },
		       { "fred", 25 },
		       { "mary", 27 },
		       { "mark", 35 },
		       { "bill", 50 }
	       };
	       const size_t len	= sizeof(friends) / sizeof(friends[0]);

	       age = 22;
	       friend =	bsearch(&age, friends, len, sizeof(friends[0]),	compare);
	       assert(strcmp(friend->name, "paul") == 0);
	       printf("name: %s\nage: %d\n", friend->name, friend->age);

	       age = 25;
	       friend =	bsearch(&age, friends, len, sizeof(friends[0]),	compare);

	       /*
		* For multiple elements	with the same key, it is implementation
		* defined which	will be	returned
		*/
	       assert(strcmp(friend->name, "fred") == 0	||
		   strcmp(friend->name,	"anne")	== 0);
	       printf("name: %s\nage: %d\n", friend->name, friend->age);

	       age = 30;
	       friend =	bsearch(&age, friends, len, sizeof(friends[0]),	compare);
	       assert(friend ==	NULL);
	       printf("friend aged 30 not found\n");
       }

SEE ALSO
       db(3), lsearch(3), qsort(3)

STANDARDS
       The bsearch() function conforms to ISO/IEC 9899:1990 ("ISO C90").

FreeBSD	13.2			 July 17, 2019			    BSEARCH(3)
NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | EXAMPLES | SEE ALSO | STANDARDS

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