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 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);
}
return 0;
}
