Why does this program crash when I run through the loop a 2nd time?

Question

Try as I might to solve this riddle, I think I'm losing my mind! Can anyone help understand why this program crashes when I run through the loop a 2nd time?

I can run through the interactive loop one time and have the values entered written to a file. However, when I attempt to pass through the a loop a 2nd time, the program chokes.

// C Libraries Used

#include <stdio.h>
#include <math.h>
#include <string.h>

// Constant definitions

const float OTPAYFACTOR = 1.5;
const float REGWORKWKHRS = 40;
FILE *payfile;                // report file (for output)

// Variable declerations
char deptname [21];
char firstname [10];
char lastname [10];
char fullname [47];
float hrsworked;
float hrwage;
float reghrsworked;
float othrsworked;
float otwage;
float grosswage;
int count;
char again;

// Function Prototypes

//**~~**~~**~~**~~**~~**~~**~~**~~**~~**~~**~~**~~**~~**~~**~~**~~**~~**~~**~~**~~
// M A I N   F U N C T I O N
//**~~**~~**~~**~~**~~**~~**~~**~~**~~**~~**~~**~~**~~**~~**~~**~~**~~**~~**~~**~~

int main (void){
    payfile = fopen("c:\\class\\mod6\\ethan-pay.txt","w");     // Open disk file
    printf("Mountain Pacific Corporation\nDepartment Salary Program\n\n");
    printf("Please enter the name of the department: ");
    scanf("%s", deptname);
    count = 0;    // Initialize this "counting" variable to zero to start
    printf("%s", deptname);
    printf("\n");
do {

      printf("Enter employee #%d: ", count+1);
      scanf("%s %s", firstname, lastname);
      fscanf(payfile,"%s %s", firstname, lastname);
      strcpy(fullname, firstname);
      strcat(fullname, " ");
      strcat(fullname, lastname);
      printf("Enter the hourly wage of %s: ", fullname);
      scanf("%f", &hrwage);
      fscanf(payfile,"%f", &hrwage);
      printf("Enter total number of hours: ");
      scanf("%f", &hrsworked);
      fscanf(payfile,"%f", &hrsworked);

    if (hrsworked <= REGWORKWKHRS){     //
        reghrsworked = hrsworked;
        othrsworked = 0;
        otwage = hrwage * OTPAYFACTOR;
        grosswage = hrwage*reghrsworked;
    }
        else{

            reghrsworked = REGWORKWKHRS;
            othrsworked = hrsworked - REGWORKWKHRS;
            otwage = hrwage * OTPAYFACTOR;
            grosswage = (reghrsworked * hrwage) + (othrsworked * otwage);
        }
       fprintf(payfile,"%-22s%0.1f ($%0.2f) %6.1f ($%0.2f) $%-4.2f\n", fullname, reghrsworked, hrwage, othrsworked, otwage, grosswage);
       printf("\nThank you. Process another employee? ");
       scanf ("%s", &again);
       printf("\n");

       count++; // Increment the counting variable


} while (again == 'Y'|| again == 'y' || again != 'N' && again != 'n');


      printf("End of processing.\n");

    fclose(payfile);
return 0;
}

Answer 1

I don't understand why are you scanning your file that you use for save the result:

scanf("%s %s", firstname, lastname);
fscanf(payfile,"%s %s", firstname, lastname);
// ...
scanf("%f", &hrwage);
fscanf(payfile,"%f", &hrwage);
// ...
scanf("%f", &hrsworked);
fscanf(payfile,"%f", &hrsworked);

What you do erase previous value. Just remove all call to fscanf() .

I strongly advice you to change your code practice, global should be avoid, only declare variable when you need them, don't ignore error code from function, provide to scanf() the max size that it can use , etc...

example probably not perfect:

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

#define OTPAYFACTOR 1.5
#define REGWORKWKHRS 40

int main(void) {
  printf("Mountain Pacific Corporation\nDepartment Salary Program\n\n"
         "Please enter the name of the department: ");
  char deptname[21];
  if (scanf("%20s", deptname) != 1) {
    return 1;
  }
  printf("%s\n", deptname);

  FILE *payfile = fopen("c:\\class\\mod6\\ethan-pay.txt", "w");
  if (!payfile) {
    return 1;
  }
  for (int count = 0;; count++) {
    printf("Enter employee #%d: ", count + 1);
    char firstname[10];
    char lastname[10];
    if (scanf("%9s %9s", firstname, lastname) != 2) {
      return 1;
    }
    char fullname[19];
    sprintf(fullname, "%s %s", firstname, lastname);
    printf("Enter the hourly wage of %s: ", fullname);
    float hrwage;
    if (scanf("%f", &hrwage) != 1) {
      return 1;
    }
    printf("Enter total number of hours: ");
    float hrsworked;
    if (scanf("%f", &hrsworked) != 1) {
      return 1;
    }
    if (hrsworked <= REGWORKWKHRS) {
      float reghrsworked = hrsworked;
      float othrsworked = 0;
      float otwage = hrwage * OTPAYFACTOR;
      float grosswage = hrwage * reghrsworked;
      fprintf(stdout, "%-22s%0.1f ($%0.2f) %6.1f ($%0.2f) $%-4.2f\n", fullname,
              reghrsworked, hrwage, othrsworked, otwage, grosswage);
    } else {
      float reghrsworked = REGWORKWKHRS;
      float othrsworked = hrsworked - REGWORKWKHRS;
      float otwage = hrwage * OTPAYFACTOR;
      float grosswage = (reghrsworked * hrwage) + (othrsworked * otwage);
      fprintf(stdout, "%-22s%0.1f ($%0.2f) %6.1f ($%0.2f) $%-4.2f\n", fullname,
              reghrsworked, hrwage, othrsworked, otwage, grosswage);
    }

    printf("\nThank you. Process another employee? ");
    char again;
    if (scanf(" %c", &again) != 1) {
      return 1;
    }
    if (again != 'Y' && again != 'y') {
      break;
    }
    printf("\n");
  }
  fclose(payfile);
  printf("End of processing.\n");
}

example input:

jurasickpark
sarah connor 5 42
y
bob lennon 9 12
n

output file:

sarah connor          40.0 ($5.00)    2.0 ($7.50) $215.00
bob lennon            12.0 ($9.00)    0.0 ($13.50) $108.00