BSEARCH(3) Linux Programmer's Manual BSEARCH(3)NAMEbsearch - 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 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, respec‐
tively, 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).
┌──────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├──────────┼───────────────┼─────────┤
│bsearch() │ Thread safety │ MT-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("'%s': unknown month\n", argv[i]);
else
printf("%s: month #%d\n", res->name, res->nr);
}
exit(EXIT_SUCCESS);
}
SEE ALSOhsearch(3), lsearch(3), qsort(3), tsearch(3)COLOPHON
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2017-09-15 BSEARCH(3)
