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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 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.

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 3.22 of the Linux man-pages project.  A description of the project,  and  informa-
       tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



                                  2003-11-01                        BSEARCH(3)