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.

ATTRIBUTES

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

   
   Interface  Attribute      Value   
   
   bsearch()  Thread safety  MT-Safe 
   

CONFORMING TO

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

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

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   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)

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