lsearch(3C)                                           lsearch(3C)



NAME
     lsearch, lfind - provide a linear search and update

SYNOPSIS
     #include <stdio.h>
     #include <search.h>

     char *lsearch(key, base, nelp, width, compar)
     char *key;
     char *base;
     unsigned *nelp;
     unsigned *width;
     int (*compar)();

     char *lfind(key, base, nelp, width, compar)
     char *key;
     char *base;
     unsigned *nelp;
     unsigned *width;
     int (*compar)();

DESCRIPTION
     lsearch is a linear search routine generalized from Knuth
     (6.1) Algorithm S.  It returns a pointer to 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.  nelp points to an integer
     containing the current number of elements in the table.  The
     integer at *nelp is incremented if the datum is added to the
     table.  width is the width of an element in bytes.  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 -1 pointer
     is returned.

EXAMPLES
     This fragment will read in < TABSIZE strings of length <
     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( );



January 1992                                                    1

lsearch(3C)                                           lsearch(3C)



           unsigned nel = 0;
           int strcmp( );
           . . .
           while (fgets(line, ELSIZE, stdin) != NULL &&
               nel < TABSIZE)
                 (void) lsearch(line, (char *)tab, &nel,
                        ELSIZE, strcmp);
           . . .


STATUS MESSAGES AND VALUES
     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.

LIMITATIONS
     Undefined results can occur if there is not enough room in
     the table to add a new item.

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.

SEE ALSO
     bsearch(3C), hsearch(3C), tsearch(3C)
























2                                                    January 1992