Manpage of BSEARCH

BSEARCH

Section: Linux Programmer's Manual (3)
Updated: 2015-08-08
Index
 

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 nmembobjects, 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 comparroutine is expected to have two arguments which point to the keyobject and to an array member, in that order, and should return an integer less than, equal to, or greater than zero if the keyobject 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).
InterfaceAttributeValue
bsearch() Thread safetyMT-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("aq%saq: 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)


 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ATTRIBUTES
CONFORMING TO
EXAMPLE
SEE ALSO

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