Man page of tw_get_categories(3)

tw_get_categories - get a list of categories

C/C++ #include <tw.h>

 tw_errno_t tw_get_categories(tw_t *tw, char ***cats);

tw_get_categories() generates a list of all categories known to the Textweiser database.

tw (tw_t *)

Pointer to an initialized Textweiser object.

cats (char ***)

Pointer to pointer to pointer to char.

Declare cats as a pointer to pointer to char and initialize it with NULL. Pass a pointer to cats to tw_get_categories().

If tw_get_categories() succeeds, cats will contain a NULL terminated array of categories.

If an error occurs or no categories could be found within the database, the value pointed to by cats is set to NULL.

APPLICATION CODE EXAMPLE:

C/C++ char **cats = NULL;

 tw_get_categories(&tw, &cats);

For a complete example, have a look at EXAMPLE below.

tw_get_categories() returns an error indicator (tw_errno_t). A return value of TW_OK indicates success, any other value discriminates the occurred error.

The function tw_strerror(3) can be used to obtain a natural language error message.

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The generated list of categories is sorted alphabetically.

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If an error occurs or no categories could be found within the database, the value pointed to by cats is set to NULL.

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On Windows, tw_free_categories(3) has to be used to free the memory allocated for the category listing. On any other OS the use of tw_free_categories(3) is recommended.

C/C++ #include <stdio.h>
 #include <stdlib.h>

 #include <tw.h>

 int main(int argc, char *argv[])
 {
     tw_errno_t   rv   = TW_OK;
     char       **cats = NULL;
     tw_t         tw   = TW_INITIALIZER;

     /* Initialize a Textweiser object using the SQLite
      * database backend. */
     rv = tw_init(&tw, NULL, NULL, NULL, "example.sqlt", 0);

     if (rv != TW_OK)
     {
         fprintf(stderr, "Failed to initialize: %s\n",
                 tw_strerror(rv));
         return EXIT_FAILURE;
     }

     rv = tw_get_categories(&tw, &cats);

     tw_free(&tw);

     if (rv == TW_OK && cats)
     {
         size_t i = 0;

         for (i = 0; cats[i]; i++)
         {
             printf("Category %02lu: \"%s\"\n",
                (unsigned long) i + 1, cats[i]);
         }

         tw_free_categories(cats);

         return EXIT_SUCCESS;
     }

     return EXIT_FAILURE;
 }

Example output:

 Category 01: "Economy & Markets"
 Category 02: "Holidays"
 Category 03: "Sports"
 Category 04: "TV"

tw_add_category(3), tw_delete_category(3), tw_rename_category(3), tw_strerror(3)

Textweiser User Manual

http://www.lingua-systems.com/text-classifier/textweiser-library/

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