.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "LSEARCH" 3P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\" lsearch 
.SH PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
.SH NAME
lsearch, lfind \- linear search and update
.SH SYNOPSIS
.LP
\fB#include <search.h>
.br
.sp
void *lsearch(const void *\fP\fIkey\fP\fB, void *\fP\fIbase\fP\fB,
size_t *\fP\fInelp\fP\fB, size_t\fP
\fIwidth\fP\fB,
.br
\ \ \ \ \ \  int (*\fP\fIcompar\fP\fB)(const void *, const void *));
.br
void *lfind(const void *\fP\fIkey\fP\fB, const void *\fP\fIbase\fP\fB,
size_t *\fP\fInelp\fP\fB,
.br
\ \ \ \ \ \  size_t width, int (*\fP\fIcompar\fP\fB)(const void *,
const void *)); \fP
\fB
.br
\fP
.SH DESCRIPTION
.LP
The \fIlsearch\fP() 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
\fIkey\fP argument points to the entry to be sought in the
table. The \fIbase\fP argument points to the first element in the
table. The \fIwidth\fP argument is the size of an element in
bytes. The \fInelp\fP argument points to an integer containing the
current number of elements in the table. The integer to which
\fInelp\fP points shall be incremented if the entry is added to the
table. The \fIcompar\fP argument points to a comparison
function which the application shall supply (for example, \fIstrcmp\fP()).
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.
.LP
The \fIlfind\fP() function shall be equivalent to \fIlsearch\fP(),
except that if the entry is not found, it is not added to
the table. Instead, a null pointer is returned.
.SH RETURN VALUE
.LP
If the searched for entry is found, both \fIlsearch\fP() and \fIlfind\fP()
shall return a pointer to it. Otherwise,
\fIlfind\fP() shall return a null pointer and \fIlsearch\fP() shall
return a pointer to the newly added element.
.LP
Both functions shall return a null pointer in case of error.
.SH ERRORS
.LP
No errors are defined.
.LP
\fIThe following sections are informative.\fP
.SH EXAMPLES
.SS Storing Strings in a Table
.LP
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.
.sp
.RS
.nf

\fB#include <stdio.h>
#include <string.h>
#include <search.h>
.sp

#define TABSIZE 50
#define ELSIZE 120
.sp

\&...
    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);
    ...
\fP
.fi
.RE
.SS Finding a Matching Entry
.LP
The following example finds any line that reads \fB"This is a test."\fP
\&.
.sp
.RS
.nf

\fB#include <search.h>
#include <string.h>
\&...
char line[ELSIZE], tab[TABSIZE][ELSIZE];
size_t nel = 0;
char *findline;
void *entry;
.sp

findline = "This is a test.\\n";
.sp

entry = lfind(findline, tab, &nel, ELSIZE, (
    int (*)(const void *, const void *)) strcmp);
\fP
.fi
.RE
.SH APPLICATION USAGE
.LP
The comparison function need not compare every byte, so arbitrary
data may be contained in the elements in addition to the
values being compared.
.LP
Undefined results can occur if there is not enough room in the table
to add a new item.
.SH RATIONALE
.LP
None.
.SH FUTURE DIRECTIONS
.LP
None.
.SH SEE ALSO
.LP
\fIhcreate\fP(), \fItsearch\fP(), the Base Definitions volume of
IEEE\ Std\ 1003.1-2001, \fI<search.h>\fP
.SH COPYRIGHT
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 .