Man Bsearch en anglais
BSEARCH(3)                 Linux Programmer's Manual                BSEARCH(3)



 

NAME


       bsearch - binary search of a sorted array

 

SYNOPSIS


       #include 

       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,  respec-
       tively, 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 
       #include 
       #include 

       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(struct mi))

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



                                  2003-11-01                        BSEARCH(3)