bsearch(3) [osf1 man page]

bsearch(3)						     Library Functions Manual							bsearch(3)

NAME

       bsearch - Performs a binary search

LIBRARY

       Standard C Library (libc)

SYNOPSIS

       #include <stdlib.h>

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

STANDARDS

       Interfaces documented on this reference page conform to industry standards as follows:

       bsearch(): XSH5.0

       Refer to the standards(5) reference page for more information about industry standards and associated tags.

PARAMETERS

       Target  of  search.  Points to the initial object in the array.	Specifies the number of elements in the array.	Specifies the byte size of
       each element of the array.  Points to the comparison function, which is called with two parameters that point to the key object and  to	an
       array member, in that order.

DESCRIPTION

       The bsearch() function does a binary search and returns a pointer in an array that indicates where an object is found.

       The  compar  comparison	function  is  called with two parameters that point to objects that are compared during the search.  This function
       returns an integer less than, equal to, or greater than 0 (zero) depending whether the object pointed to by the key parameter is considered
       to be less than, equal to, or greater than the array element.

NOTES

       [Tru64 UNIX]  The bsearch() function is reentrant, but care should be taken to ensure that the function supplied as argument compar is also
       reentrant.

RETURN VALUES

       Upon successful completion, the bsearch() function returns a pointer to a matching object in the array.	A NULL is returned when  no  match
       is found.  When two or more objects compare equally, the returned object is unspecified.

RELATED INFORMATION

       Functions: hsearch(3), lsearch(3), qsort(3), tsearch(3)

       Standards: standards(5) delim off

																	bsearch(3)

BSEARCH(3)						     Linux Programmer's Manual							BSEARCH(3)

NAME

       bsearch - binary search of a sorted array

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  rou-
       tine  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, respectively, to be less than, to match, or be greater than the array
       member.

RETURN VALUE

       The  bsearch()  function returns a pointer to a matching member of the array, or NULL if no match is found.  If there are multiple elements
       that match the key, the element returned is unspecified.

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(7).

       +----------+---------------+---------+
       |Interface | Attribute	  | Value   |
       +----------+---------------+---------+
       |bsearch() | Thread safety | MT-Safe |
       +----------+---------------+---------+

CONFORMING TO

       POSIX.1-2001, POSIX.1-2008, C89, C99, SVr4, 4.3BSD.

EXAMPLE

       The example below first sorts an array of structures using qsort(3), then retrieves desired elements using bsearch().

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

       struct mi {
	   int nr;
	   char *name;
       } months[] = {
	   { 1, "jan" }, { 2, "feb" }, { 3, "mar" }, { 4, "apr" },
	   { 5, "may" }, { 6, "jun" }, { 7, "jul" }, { 8, "aug" },
	   { 9, "sep" }, {10, "oct" }, {11, "nov" }, {12, "dec" }
       };

       #define nr_of_months (sizeof(months)/sizeof(months[0]))

       static int
       compmi(const void *m1, const void *m2)
       {
	   struct mi *mi1 = (struct mi *) m1;
	   struct mi *mi2 = (struct mi *) m2;
	   return strcmp(mi1->name, mi2->name);
       }

       int
       main(int argc, char **argv)
       {
	   int i;

	   qsort(months, nr_of_months, sizeof(struct mi), compmi);
	   for (i = 1; i < argc; i++) {
	       struct mi key, *res;
	       key.name = argv[i];
	       res = bsearch(&key, months, nr_of_months,
			     sizeof(struct mi), compmi);
	       if (res == NULL)
		   printf("'%s': unknown month
", argv[i]);
	       else
		   printf("%s: month #%d
", res->name, res->nr);
	   }
	   exit(EXIT_SUCCESS);
       }

SEE ALSO

       hsearch(3), lsearch(3), qsort(3), tsearch(3)

COLOPHON

       This page is part of release 4.15 of the Linux man-pages project.  A description of the project, information about reporting bugs, and  the
       latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.

								    2017-09-15								BSEARCH(3)