NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | CONFORMING TO | EXAMPLE | SEE ALSO | COLOPHON
BSEARCH(3) Linux Programmer's Manual BSEARCH(3)
bsearch - binary search of a sorted array
#include <stdlib.h>
void *bsearch(const void *key, const void *base,
size_t nmemb, size_t size,
int (*compar)(const void *, const void *));
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.
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.
SVr4, 4.3BSD, POSIX.1-2001, C89, C99.
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);
}
hsearch(3), lsearch(3), qsort(3), tsearch(3)
This page is part of release 3.23 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)