SIMPLE SOLUTIONS

BSEARCH - reference manual online

Binary search of a sorted array.

Chapter
2015-08-08
BSEARCH(3)                          Linux Programmer's Manual                          BSEARCH(3)

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 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 inte‐ ger 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.
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 ALSO hsearch(3), lsearch(3), qsort(3), tsearch(3)
COLOPHON This page is part of release 4.04 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at http://www.kernel.org/doc/man-pages/.
2015-08-08 BSEARCH(3)
This manual Reference Other manuals
bsearch(3) referred by hsearch(3) | lsearch(3) | qsort(3) | tsearch(3)
refer to attributes(7) | hsearch(3) | lsearch(3) | qsort(3) | tsearch(3)