bsearch(3) - phpMan

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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 com-
       parison 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 ele-
       ment 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 information about reporting bugs, can be found at  http://www.ker-
       nel.org/doc/man-pages/.



                                  2003-11-01                        BSEARCH(3)

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