LSEARCH(3P)                                         POSIX Programmer's Manual                                        LSEARCH(3P)



PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (con-
       sult the corresponding Linux manual page for details of Linux behavior), or the  interface  may  not  be  implemented  on
       Linux.

NAME
       lsearch, lfind - linear search and update

SYNOPSIS
       #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 *));


DESCRIPTION
       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 ta-
       ble. Instead, a null pointer is returned.

RETURN VALUE
       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.

ERRORS
       No errors are defined.

       The following sections are informative.

EXAMPLES
   Storing Strings in a Table
       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);
                  ...

   Finding a Matching Entry
       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);

APPLICATION USAGE
       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.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       hcreate(), tsearch(), the Base Definitions volume of IEEE Std 1003.1-2001, <search.h>

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,  Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                   LSEARCH(3P)