Originální popis anglicky:
lsearch, lfind - linear search and update
Návod, kniha: POSIX Programmer's Manual
#include <search.h>
void *lsearch(const void *
key, void
*base , size_t
*nelp , size_t
width ,
int (*
compar )(const void *, const void *));
void *lfind(const void *
key, const void
*base , size_t
*nelp ,
size_t width, int (*
compar )(const void *, const void *));
The
lsearch() function shall linearly search the table and return a
pointer into the table for the matching entry. If the entry does not occur, it
shall be 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
width argument is the size of an element in
bytes. The
nelp argument points to an integer containing the current
number of elements in the table. The integer to which
nelp points shall
be incremented if the entry is added to the table. The
compar argument
points to a comparison function which the application shall supply (for
example,
strcmp()). It is called with two arguments that point to the
elements being compared. The application shall ensure that the function
returns 0 if the elements are equal, and non-zero otherwise.
The
lfind() function shall be equivalent to
lsearch(), except that
if the entry is not found, it is not added to the table. Instead, a null
pointer is returned.
If the searched for entry is found, both
lsearch() and
lfind()
shall return a pointer to it. Otherwise,
lfind() shall return a null
pointer and
lsearch() shall return a pointer to the newly added
element.
Both functions shall return a null pointer in case of error.
No errors are defined.
The following sections are informative.
This fragment reads in less than or equal to TABSIZE strings of length less than
or equal to ELSIZE and stores them in a table, eliminating duplicates.
#include <stdio.h>
#include <string.h>
#include <search.h>
#define TABSIZE 50
#define ELSIZE 120
...
char line[ELSIZE], tab[TABSIZE][ELSIZE];
size_t nel = 0;
...
while (fgets(line, ELSIZE, stdin) != NULL && nel < TABSIZE)
(void) lsearch(line, tab, &nel,
ELSIZE, (int (*)(const void *, const void *)) strcmp);
...
The following example finds any line that reads
"This is a
test." .
#include <search.h>
#include <string.h>
...
char line[ELSIZE], tab[TABSIZE][ELSIZE];
size_t nel = 0;
char *findline;
void *entry;
findline = "This is a test.\n";
entry = lfind(findline, tab, &nel, ELSIZE, (
int (*)(const void *, const void *)) 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.
Undefined results can occur if there is not enough room in the table to add a
new item.
None.
None.
hcreate() ,
tsearch() , the Base Definitions volume of
IEEE Std 1003.1-2001,
<search.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html
.
