lsearch, lfind - linear search and update


     #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 *));


     The lsearch() function is a linear search  routine  general-
     ized  from Knuth (6.1) Algorithm S. (See The Art of Computer
     Programming, Volume 3, Section 6.1, by Donald E.  Knuth.) It
     returns  a pointer into a table indicating where a datum may
     be found. If the datum does not occur, it is  added  at  the
     end  of  the table.  The key argument points to the datum to
     be sought in the table.  The base  argument  points  to  the
     first  element in the table.  The nelp argument points to an
     integer containing the current number of   elements  in  the
     table.  The  integer is incremented if the datum is added to
     the table.  The  width argument is the size of an element in
     bytes.   The  compar argument is a pointer to the comparison
     function that the user must supply (  strcmp(3C)  for  exam-
     ple). It is called with two arguments that point to the ele-
     ments being compared.  The function must return zero if  the
     elements are equal and non-zero otherwise.

     The lfind() function is the same as  lsearch()  except  that
     if  the  datum  is  not found, it is not added to the table.
     Instead, a null pointer is returned.

     It is important to note the following:

        o  the pointers to the key and the element at the base of
           the table may be pointers to any type.

        o  The comparison function need not compare  every  byte,
           so  arbitrary data may be contained in the elements in
           addition to the values being compared.

        o  The value returned should be cast into  type  pointer-


     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


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


     Example 1: A sample code using the lsearch() function.

     This program will read  in  less  than  TABSIZE  strings  of
     length less than ELSIZE and store them in a table, eliminat-
     ing duplicates, and then will print each entry.

     #include <search.h>
     #include <string.h>
     #include <stdlib.h>
     #include <stdio.h>

     #define TABSIZE 50
     #define ELSIZE 120

             char line[ELSIZE];              /* buffer to hold input string */
             char tab[TABSIZE][ELSIZE];      /* table of strings */
             size_t nel = 0;                 /* number of entries in tab */
             int i;

             while (fgets(line, ELSIZE, stdin) != NULL &&
                     nel < TABSIZE)
                     (void) lsearch(line, tab, &nel, ELSIZE, mycmp);
             for( i = 0; i < nel; i++ )
                     (void)fputs(tab[i], stdout);
             return 0;


     See attributes(5) for descriptions of the  following  attri-

    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    | MT-Level                    | Safe                        |


     bsearch(3C), hsearch(3C),  string(3C),  tsearch(3C),  attri-

     The Art of  Computer  Programming,  Volume  3,  Sorting  and
     Searching  by  Donald  E. Knuth, published by Addison-Wesley
     Publishing Company, 1973.

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