LSEARCH(3C)LSEARCH(3C)NAME
lsearch, lfind - linear search and update
SYNOPSIS
#include <stdio.h>
#include <search.h>
void *lsearch ((const void *)key, (void *)base,
size_t *nmemb, size_t size,
int (*compar)(const void *, const void *));
void *lfind ((const void *)key, (const void *)base,
size_t *nmemb, size_t size,
int (*compar)(const void *, const void *));
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. Nmemb 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. Size is the size of the key in bytes
(sizeof (*key)). 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 less than TABSIZE strings of length less than
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;
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LSEARCH(3C)LSEARCH(3C)
int strcmp( );
. . .
while (fgets(line, ELSIZE, stdin) != NULL &&
nel < TABSIZE)
(void) lsearch(line, (char *)tab, &nel,
ELSIZE, strcmp);
. . .
SEE ALSObsearch(3C), hsearch(3C), string(3C), tsearch(3C).
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.
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