bsearch(3) [x11r4 man page]

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)