void *lsearch (const void *key, void *base, size_t *nelp, size_twidth, int (*compar) (const void *));
void *lfind (const void *key, const void *base, size_t, *nelp, size_twidth, int (*compar) (const void *, const void * ));
lfind- searches for object and adds to table
The lsearch function is a linear search routine generalized from Knuth (6.1) Algorithm S. It returns a pointer into a table indicating where an entry may be found. If the entry does not occur, it is added at the end of the table. The key argument points to the entry to be sought in the table. The base argument points to the first element in the table. The nelp argument points to an integer containing the current number of elements in the table. The width argument is the size of an element in bytes. The integer is incremented if the entry is added to the table. The compar argument is the name of the comparison function which the user must supply (strcmp, for example). It is called with two arguments that point to the elements being compared. The function must return zero if the elements are equal and non-zero otherwise.
The lfind function is the same as
lsearch except that if the entry is not found,
it is not added to the table.
Instead, a NULL pointer is returned.
#include <stdio.h> #include <search.h>
#define TABSIZE 50 #define ELSIZE 120
char line[ELSIZE], tab[TABSIZE][ELSIZE], *lsearch( ); size_t nel = 0; int strcmp( ); . . . while (fgets(line, ELSIZE, stdin) != NULL && nel < TABSIZE) (void) lsearch((void *)line, (tab *)tab, &nel, ELSIZE, strcmp); . . .
The comparison function need not compare every byte, so arbitrary data may be contained in the elements in addition to the values being compared.
Although declared as type pointer-to-character, the value returned should be cast into type pointer-to-element.
Undefined results can occur if there is not enough room in the table to add a new item.
X/Open Portability Guide, Issue 3, 1989 .