1BSEARCH(3)                 Linux Programmer's Manual                BSEARCH(3)
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NAME

6       bsearch - binary search of a sorted array
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SYNOPSIS

9       #include <stdlib.h>
10
11       void *bsearch(const void *key, const void *base, size_t nmemb,
12              size_t size, int (*compar)(const void *, const void *));
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DESCRIPTION

15       The  bsearch() function searches an array of nmemb objects, the initial
16       member of which is pointed to by base, for a member  that  matches  the
17       object  pointed  to  by  key.   The size of each member of the array is
18       specified by size.
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20       The contents of the array should be in ascending sorted order according
21       to the comparison function referenced by compar.  The compar routine is
22       expected to have two arguments which point to the key object and to  an
23       array  member,  in  that order, and should return an integer less than,
24       equal to, or greater than zero if the  key  object  is  found,  respec‐
25       tively, to be less than, to match, or be greater than the array member.
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RETURN VALUE

28       The  bsearch()  function  returns a pointer to a matching member of the
29       array, or NULL if no match is found.  If there  are  multiple  elements
30       that match the key, the element returned is unspecified.
31

EXAMPLE

33       The  example  below  first sorts an array of structures using qsort(3),
34       then retrieves desired elements using bsearch().
35
36       #include <stdio.h>
37       #include <stdlib.h>
38       #include <string.h>
39
40       struct mi {
41            int nr;
42            char *name;
43       } months[] = {
44            { 1, "jan" }, { 2, "feb" }, { 3, "mar" }, { 4, "apr" },
45            { 5, "may" }, { 6, "jun" }, { 7, "jul" }, { 8, "aug" },
46            { 9, "sep" }, {10, "oct" }, {11, "nov" }, {12, "dec" }
47       };
48
49       #define nr_of_months (sizeof(months)/sizeof(months[0]))
50
51       static int compmi(const void *m1, const void *m2) {
52            struct mi *mi1 = (struct mi *) m1;
53            struct mi *mi2 = (struct mi *) m2;
54            return strcmp(mi1->name, mi2->name);
55       }
56
57       int main(int argc, char **argv) {
58            int i;
59
60            qsort(months, nr_of_months, sizeof(struct mi), compmi);
61            for (i = 1; i < argc; i++) {
62                 struct mi key, *res;
63                 key.name = argv[i];
64                 res = bsearch(&key, months, nr_of_months,
65                            sizeof(struct mi), compmi);
66                 if (res == NULL)
67                      printf("'%s': unknown month\n", argv[i]);
68                 else
69                      printf("%s: month #%d\n", res->name, res->nr);
70            }
71            return 0;
72       }
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CONFORMING TO

75       SVr4, 4.3BSD, POSIX.1-2001, C89, C99
76

SEE ALSO

78       hsearch(3), lsearch(3), qsort(3), tsearch(3)
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82                                  2003-11-01                        BSEARCH(3)
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