Program Help

**omalleys** · 06-17-2002

I need help figuring out how to change the below program so that its output is sent to a file.

#include
/*Jason Jones */
main ()
{
int day_code, /* day_code = 0 means the month starts on Sun
day_code = 1 means the month starts on Mon
day_code = 2 means the month starts on Tues, etc */
days_in_month, /* number of days in month currently being
printed */
leap_year, /* 1 means leap year; 0 means no leap year */
day, /*counter for day of month */
month; /* month = 1 is Jan, month =2 is Feb, etc */
do {
printf (“Enter day and leap year codes: “);
scanf (“%d%d”, &day_code, &leap_year);
} while (day_code < 0 || day_code > 6 );
for (month = 1; month <= 12; month ++) {
switch (month) { /* print name and set days_in_month */

case 1:
printf(“\n\nJanuary”);
days_in_month = 31;
break;
case 2:
printf(“\n\nFebruary”);
days_in_month = leap_year ? 29 : 28;
break;
case 3:
printf(“\n\nMarch”);
days_in_month = 31;
break;
case 4:
printf(“\n\nApril”);
days_in_month = 30;
break;
case 5:
printf(“\n\nMay”);
days_in_month = 31;
break;
case 6:
printf(“\n\nJune”);
days_in_month = 30;
break;
case 7:
printf(“\n\nJuly”);
days_in_month = 31;
break;
case 8:
printf(“\n\nAugust”);
days_in_month = 31;
break;
case 9:
printf(“\n\nSeptember”);
days_in_month = 30;
break;

case 10:
printf(“\n\nOctober”);
days_in_month = 31;
break;
case 11:
printf(“\n\nNovember”);
days_in_month = 30;
break;
case 1:
printf(“\n\nDecember”);
days_in_month = 31;
break;
}
printf( ‘\n\nSun Mon Tue Wed Thu Fri Sat\n”);
/* advance printer to correct position for first date */
for (day =1; day <=1 + day_code * 5; day++) {
printf(“ “);
/* print the dates for one month */
for ( day = 1; day <= days_in_month; day++) {
printf(“%2d’, day);
if ( (day + day_code) % 7 > 0 ) /* before Sat? */
/* move to next day in same week */
printf(“ “);
else /*skip to next line to start with Sun */
printf(“\n”);
}
/* set day_code for next month to begin */
day_code = (day_code + days_in_month) % 7;
}
}

**sean345** · 06-17-2002

Instead of using printf, use fprintf and open a file.

Code:

FILE *outfile = fopen("FileName", "w");
fprintf(outfile, "This is the output\n");
//more fprints.

;

or you could change stdout to the file.

Code:

FILE *outfile = fopen("FileName", "w");
stdout = outfile;
//printfs go here

- Sean

**omalleys** · 06-17-2002

do you have to use that line for all of the printf lines or just the one?

**mackster** · 06-17-2002

u need to open the file only once and use fprintf multiple times to write to that file

**Prelude** · 06-18-2002

Here's the idea:

Code:

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

struct monthData
{
  char *monthName;
  int monthDays;
};

static const struct monthData MD[] =
{
  {"January",31},
  {"February",28},
  {"March",31},
  {"April",30},
  {"May",31},
  {"June",30},
  {"July",31},
  {"August",31},
  {"September",30},
  {"October",31},
  {"November",30},
  {"December",31},
};

int main ( void )
{
  FILE *outputFile;
  int day_code = 0, 
      days_in_month = 0, 
      leap_year = 0, 
      day, 
      month;

  outputFile = fopen ( "dataout.txt", "w" );
  if ( outputFile == NULL ) {
    perror ( "File open error: outputFile" );
    return EXIT_FAILURE;
  }

  do { 
    printf ("Enter day and leap year codes: "); 
    scanf ("%d%d", &day_code, &leap_year); 
  } while (day_code < 0 || day_code > 6 );
  
  for (month = 0; month < 12; month++) {
    fprintf ( outputFile, "\n\n%s", MD[month].monthName );
    if ( month == 1 )
      /* Check for February and leap year */
      days_in_month = leap_year ? MD[month].monthDays + 1 : MD[month].monthDays;
    else
      days_in_month = MD[month].monthDays;
    /* Calculate and write one month to file */
    fprintf(outputFile, "\n\nSun Mon Tue Wed Thu Fri Sat\n");  
    for (day =1; day <= 1 + day_code * 5; day++) { 
      fprintf(outputFile, " "); 
      for ( day = 1; day <= days_in_month; day++) { 
        fprintf(outputFile, "%2d", day); 
        if ( (day + day_code) % 7 > 0 )
          fprintf(outputFile, " "); 
        else
        fprintf(outputFile, "\n"); 
      } 
      day_code = (day_code + days_in_month) % 7; 
    } 
  }
  return 0;
}

I also implemented a method that would make your program a bit shorter and easier to follow by removing the long switch statement. I used the option of placing the month name and number of days in an array of structs, but this method would also work with two arrays; one holding the names and one holding the days.

-Prelude

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