LSEARCH(3)

NAME
lsearch, lfind - linear search and update

SYNOPSIS
#include <stdio.h>
#include <search.h>

char *lsearch (key, base, nelp, width, compar)
char *key;
char *base;
unsigned int *nelp;
unsigned int width;
int (*compar)();

char *lfind (key, base, nelp, width, compar)
char *key;
char *base;
unsigned int *nelp;
unsigned int width;
int (*compar)();

DESCRIPTION

lsearch() is a linear search routine generalized from Knuth (6.1) Algorithm S. It returns a pointer into a table indicating where a datum may be found. If the datum does not occur, it is added at the end of the table. key points to the datum to be sought in the table. base points to the first element in the table. nelp points to an integer containing the current number of elements in the table. The integer is incremented if the datum is added to the table. compar 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.

lfind() is the same as lsearch() except that if the datum is not found, it is not added to the table. Instead, a NULL pointer is returned.

NOTES
The pointers to the key and the element at the base of the table should be of type pointer-to-element, and cast to type pointer-to-character.

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.

EXAMPLE

This fragment will read in ≤ TABSIZE strings of length ≤ ELSIZE and store them in a table, eliminating duplicates.

    #include <stdio.h>
    #include <search.h>
    #define
    TABSIZE 50
    #define
    ELSIZE 120
    	char line[ELSIZE], tab[TABSIZE][ELSIZE], *lsearch( );
    	unsigned nel = 0;
    	int strcmp( );
    	. . .
    	while (fgets(line,
    	ELSIZE, stdin) != NULL &&
    	   nel < TABSIZE)
    		 (void) lsearch(line, (char *)tab, &nel, ELSIZE, strcmp);
    	. . .

SEE ALSO
bsearch(3), hsearch(3), tsearch(3)

DIAGNOSTICS
If the searched for datum is found, both lsearch() and lfind() return a pointer to it. Otherwise, lfind() returns NULL and lsearch() returns a pointer to the newly added element.

BUGS
Undefined results can occur if there is not enough room in the table to add a new item.