lsearch(3C)                                           lsearch(3C)



     NAME
          lsearch, lfind - 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 into a table indi-
          cating 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 con-
          taining 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 argu-
          ments that point to the elements being compared.  The func-
          tion 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.

     RETURN VALUE
          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.

     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 ar-
          bitrary data may be contained in the elements in addition to



     April, 1990                                                     1

     lsearch(3C)                                           lsearch(3C)



          the values being compared.
          Although declared as type pointer-to-character, the value
          returned should be cast into type pointer-to-element.

     EXAMPLES
          This fragment will read in < TABSIZE strings of length < EL-
          SIZE 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( );
             unsigned nel = 0;
             int strcmp( );
             . . .
             while (fgets(line, ELSIZE, stdin) != NULL &&
                 nel < TABSIZE)
                   (void) lsearch(line, (char *)tab, &nel,
                          ELSIZE, strcmp);
             . . .

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

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

























     2                                                     April, 1990