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   bsearch    ( 3 )

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Имя (Name)

bsearch - binary search of a sorted array

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Синопсис (Synopsis)

#include <stdlib.h>

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

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Описание (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.

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Возвращаемое значение (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.

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Атрибуты (Attributes)

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

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

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Стандарты (Conforming to)

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

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Примеры (Examples)

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

       int
       main(int argc, char *argv[])
       {
           qsort(months, nr_of_months, sizeof(months[0]), compmi);
           for (int i = 1; i < argc; i++) {
               struct mi key;
               struct mi *res;

               key.name = argv[i];
               res = bsearch(&key, months, nr_of_months,
                             sizeof(months[0]), compmi);
               if (res == NULL)
                   printf("'%s': unknown month\n", argv[i]);
               else
                   printf("%s: month #%d\n", res->name, res->nr);
           }
           exit(EXIT_SUCCESS);
       }

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Смотри также (See also)

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

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