lsearch(3C) — sys5



LSEARCH(3C)     DOMAIN/IX Reference Manual (SYS5)     LSEARCH(3C)



NAME
     lsearch, lfind - linear search and update

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

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

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

DESCRIPTION
     Lsearch is a linear search routine that was generalized from
     Knuth (6.1) Algorithm S.  It returns a pointer into a table
     indicating where a datum may be found.  If the datum does
     not exist, it is added to the end of the table.  Key points
     to the datum that the routine will search for in the table.
     Base points to the first element in the table.  Nelp points
     to an integer that contains the number of elements in the
     table.  The integer is incremented if the datum is added to
     the table.  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 it does not add the
     datum if it is not found in the table.  Instead, it returns
     a NULL pointer.

EXAMPLE
     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( );
               unsigned nel = 0;
               int strcmp( );
               . . .
               while (fgets(line, ELSIZE, stdin) != NULL &&
                  nel < TABSIZE)



Printed 5/10/85                                         LSEARCH-1



LSEARCH(3C)     DOMAIN/IX Reference Manual (SYS5)     LSEARCH(3C)



                    (void) lsearch(line, (char *)tab, &nel,
                           ELSIZE, strcmp);
               . . .

NOTES
     Unexpected results will occur if the table is too full to
     accept a new item.

     The pointers to the key and to 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 can 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.

DIAGNOSTICS
     If 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.

RELATED INFORMATION
     bsearch(3C), hsearch(3C), tsearch(3C).





























LSEARCH-2                                         Printed 5/10/85

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