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

6       bsearch - binary search of a sorted array
7

SYNOPSIS

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

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

29       The  bsearch()  function  returns a pointer to a matching member of the
30       array, or NULL if no match is found.  If there  are  multiple  elements
31       that match the key, the element returned is unspecified.
32

CONFORMING TO

34       SVr4, 4.3BSD, POSIX.1-2001, C89, C99.
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EXAMPLE

37       The  example  below  first sorts an array of structures using qsort(3),
38       then retrieves desired elements using bsearch().
39
40       #include <stdio.h>
41       #include <stdlib.h>
42       #include <string.h>
43
44       struct mi {
45           int nr;
46           char *name;
47       } months[] = {
48           { 1, "jan" }, { 2, "feb" }, { 3, "mar" }, { 4, "apr" },
49           { 5, "may" }, { 6, "jun" }, { 7, "jul" }, { 8, "aug" },
50           { 9, "sep" }, {10, "oct" }, {11, "nov" }, {12, "dec" }
51       };
52
53       #define nr_of_months (sizeof(months)/sizeof(months[0]))
54
55       static int
56       compmi(const void *m1, const void *m2)
57       {
58           struct mi *mi1 = (struct mi *) m1;
59           struct mi *mi2 = (struct mi *) m2;
60           return strcmp(mi1->name, mi2->name);
61       }
62
63       int
64       main(int argc, char **argv)
65       {
66           int i;
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68           qsort(months, nr_of_months, sizeof(struct mi), compmi);
69           for (i = 1; i < argc; i++) {
70               struct mi key, *res;
71               key.name = argv[i];
72               res = bsearch(&key, months, nr_of_months,
73                             sizeof(struct mi), compmi);
74               if (res == NULL)
75                   printf("'%s': unknown month\n", argv[i]);
76               else
77                   printf("%s: month #%d\n", res->name, res->nr);
78           }
79           exit(EXIT_SUCCESS);
80       }
81

SEE ALSO

83       hsearch(3), lsearch(3), qsort(3), tsearch(3)
84

COLOPHON

86       This page is part of release 3.25 of the Linux  man-pages  project.   A
87       description  of  the project, and information about reporting bugs, can
88       be found at http://www.kernel.org/doc/man-pages/.
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92                                  2003-11-01                        BSEARCH(3)
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