program12_03.c

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/* Program 12.3 Messing about with formatted file I/O */
#include <stdio.h>
#include <stdlib.h>

int main(void)
{
  long num1 = 234567L;                       /* Input values...              */
  long num2 = 345123L;
  long num3 = 789234L;

  long num4 = 0L;                            /* Values read from the file... */
  long num5 = 0L;
  long num6 = 0L;

  float fnum = 0.0f;                         /* Value read from the file     */
  int   ival[6] = { 0 };                     /* Values read from the file    */
  FILE *pfile = NULL;                        /* File pointer                 */
  char *filename = "C:\\myfile.txt";


  pfile = fopen(filename, "w");                 /* Create file to be written */
  if(pfile == NULL)
  {
    printf("Error opening %s for writing. Program terminated.", filename);
    exit(1);
  }
  fprintf(pfile, "%6ld%6ld%6ld", num1, num2, num3);   /* Write file          */
  fclose(pfile);                                      /* Close file          */
  printf("\n %6ld %6ld %6ld", num1, num2, num3);   /* Display values written */

  pfile = fopen(filename, "r");                       /* Open file to read   */
  fscanf(pfile, "%6ld%6ld%6ld", &num4, &num5 ,&num6); /* Read back           */
  printf("\n %6ld %6ld %6ld", num4, num5, num6);      /* Display what we got */

  rewind(pfile);                          /* Go to the beginning of the file */
  fscanf(pfile, "%2d%3d%3d%3d%2d%2d%3f", &ival[0], &ival[1], /* Read it again */
                      &ival[2], &ival[3], &ival[4] , &ival[5], &fnum);
  fclose(pfile);                                    /* Close the file and    */
  remove(filename);                                 /* delete physical file. */

  /* Output the results */
  printf("\n");
  for(int i = 0 ; i < 6 ; i++ )
    printf("%sival[i] = %d", i == 4 ? "\n\t" : "\t", i, ival[i]);
  printf("\nfnum = %f\n", fnum);
  return 0;
}