NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ATTRIBUTES | CONFORMING TO | EXAMPLE | SEE ALSO | COLOPHON

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

NAME         top

       bsearch - binary search of a sorted array

SYNOPSIS         top

       #include <stdlib.h>

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

DESCRIPTION         top

       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         top

       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         top

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

       ┌──────────┬───────────────┬─────────┐
       │Interface Attribute     Value   │
       ├──────────┼───────────────┼─────────┤
       │bsearch() │ Thread safety │ MT-Safe │
       └──────────┴───────────────┴─────────┘

CONFORMING TO         top

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

EXAMPLE         top

       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         top

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

COLOPHON         top

       This page is part of release 4.07 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/.

                                 2015-08-08                       BSEARCH(3)