freebsd-nq/lib/libc/stdlib/lsearch.3

.\"
.\" Initial implementation:
.\" Copyright (c) 2002 Robert Drehmel
.\" All rights reserved.
.\"
.\" As long as the above copyright statement and this notice remain
.\" unchanged, you can do what ever you want with this file.
.\"
.\" $FreeBSD$
.\"
.Dd April 17, 2016
.Dt LSEARCH 3
.Os
.Sh NAME
.Nm lsearch ,
.Nm lfind
.Nd linear search and append
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In search.h
.Ft "void *"
.Fo lsearch
.Fa "const void *key" "void *base" "size_t *nelp" "size_t width"
.Fa "int \*[lp]*compar\*[rp]\*[lp]const void *, const void *\*[rp]"
.Fc
.Ft "void *"
.Fo lfind
.Fa "const void *key" "const void *base" "size_t *nelp" "size_t width"
.Fa "int \*[lp]*compar\*[rp]\*[lp]const void *, const void *\*[rp]"
.Fc
.Sh DESCRIPTION
The
.Fn lsearch
and
.Fn lfind
functions walk linearly through an array and compare each element with
the one to be sought using a supplied comparison function.
.Pp
The
.Fa key
argument
points to an element that matches the one that is searched.
The array's address in memory is denoted by the
.Fa base
argument.
The width of one element (i.e., the size as returned by
.Fn sizeof )
is passed as the
.Fa width
argument.
The number of valid elements contained in the array (not the number of
elements the array has space reserved for) is given in the integer pointed
to by
.Fa nelp .
The
.Fa compar
argument points to a function which compares its two arguments and returns
zero if they are matching, and non-zero otherwise.
.Pp
If no matching element was found in the array,
.Fn lsearch
copies
.Fa key
into the position after the last element and increments the
integer pointed to by
.Fa nelp .
.Sh RETURN VALUES
The
.Fn lsearch
and
.Fn lfind
functions
return a pointer to the first element found.
If no element was found,
.Fn lsearch
returns a pointer to the newly added element, whereas
.Fn lfind
returns
.Dv NULL .
Both functions return
.Dv NULL
if an error occurs.
.Sh EXAMPLES
.Bd -literal
#include <search.h>
#include <stdio.h>
#include <stdlib.h>

static int
element_compare(const void *p1, const void *p2)
{
	int left = *(const int *)p1;
	int right = *(const int *)p2;

	return (left - right);
}

int
main(int argc, char **argv)
{
	const int array[10] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
	size_t element_size = sizeof(array[0]);
	size_t array_size = sizeof(array) / element_size;
	int key;
	void *element;

	printf("Enter a number: ");
	if (scanf("%d", &key) != 1) {
		printf("Bad input\en");
		return (EXIT_FAILURE);
	}

	element = lfind(&key, array, &array_size, element_size,
	    element_compare);

	if (element != NULL)
		printf("Element found: %d\en", *(int *)element);
	else
		printf("Element not found\en");

	return (EXIT_SUCCESS);
}
.Ed
.Sh SEE ALSO
.Xr bsearch 3 ,
.Xr hsearch 3 ,
.Xr tsearch 3
.Sh STANDARDS
The
.Fn lsearch
and
.Fn lfind
functions conform to
.St -p1003.1-2001 .
.Sh HISTORY
The
.Fn lsearch
and
.Fn lfind
functions appeared in
.Bx 4.2 .
In
.Fx 5.0 ,
they reappeared conforming to
.St -p1003.1-2001 .