program7_12.c

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/* Program 7.12 Arrays of Pointers to Strings */
#include <stdio.h>

const size_t BUFFER_LEN = 512;              /* Size of input buffer      */

int main(void)
{
  char buffer[BUFFER_LEN];                  /* Store for strings         */
  char *pS[3] = { NULL };                   /* Array of string pointers  */
  char *pbuffer = buffer;                   /* Pointer to buffer         */
  size_t index = 0;                         /* Available buffer position */

  printf("\nEnter 3 messages that total less than %u characters.", BUFFER_LEN-2);

  /* Read the strings from the keyboard */
  for(int i=0 ; i<3 ; i++)
  {
    printf("\nEnter %s message\n", i>0 ? "another" : "a" );
    pS[i] = &buffer[index];                 /* Save start of string      */

    /* Read up to the end of buffer if necessary */
    for( ; index<BUFFER_LEN ; index++)      /* If you read \n ... */
      if((*(pbuffer+index) = getchar()) == '\n')
        {
          *(pbuffer+index++) = '\0';        /* ...substitute \0   */
          break;
        }

    /* Check for buffer capacity exceeded */
    if((index == BUFFER_LEN) && ((*(pbuffer+index-1) != '\0') || (i<2)))
    {
      printf("\nYou ran out of space in the buffer.");
      return 1;
    }
  }

  printf("\nThe strings you entered are:\n\n");
  for(int i = 0 ; i<3 ; i++)
    printf("%s\n", pS[i]);

  printf("The buffer has %d characters unused.\n",
                     BUFFER_LEN-index);
  return 0;
}