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Linux 2.6 - man page for bsearch (linux section 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 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 inte-
       ger 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.

CONFORMING TO
       SVr4, 4.3BSD, POSIX.1-2001, C89, C99.

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\n", argv[i]);
	       else
		   printf("%s: month #%d\n", res->name, res->nr);
	   }
	   exit(EXIT_SUCCESS);
       }

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

COLOPHON
       This page is part of release 3.55 of the Linux man-pages project.  A  description  of  the
       project,     and    information	  about    reporting	bugs,	 can	be    found    at
       http://www.kernel.org/doc/man-pages/.

					    2003-11-01				       BSEARCH(3)


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