When I run the program the first time (the output file is not yet created), it works fine. But when I run it again (output file exists), it gives a segmentation fault after reading the last input.
From looking at the problem, it looks like it has something to do with my file handling, but when I tried to debug, I found out that I get the seg. fault before exiting the for loop in main()
.
#include <stdio.h>
#define EMPS 3
struct employee开发者_如何学运维
{
char firstname[40];
char lastname[40];
int id;
};
typedef struct employee Employee;
/* Input the employee data interactively from the keyboard */
void InputEmployeeRecord(Employee *ptrEmp);
/* Display the contents of a given Employee record */
void PrintEmployeeRecord(const Employee e);
/* Save the contents of the employee record list to the newly
created text file specified by FileName */
void SaveEmployeeRecord(const Employee e[], const char *FileName);
int id = 0;
int main()
{
Employee employees[EMPS];
for(int i = 0; i < EMPS; i++)
{
InputEmployeeRecord(&(employees[i]));
PrintEmployeeRecord(employees[i]);
}
SaveEmployeeRecord(employees, "employee.dat");
return 0;
}
void InputEmployeeRecord(Employee *ptrEmp)
{
printf("Enter first name\n");
scanf("%s", ptrEmp->firstname);
printf("Enter last name\n");
scanf("%s", ptrEmp->lastname);
ptrEmp->id = ++id;
}
void PrintEmployeeRecord(const Employee e)
{
printf("Employee %d: %s %s\n", e.id, e.firstname, e.lastname);
}
void SaveEmployeeRecord(const Employee e[], const char *FileName)
{
FILE* fptr = fopen(FileName, "r");
/* File doesn't exist */
if(fptr == NULL)
{
fclose(fptr);
// Create the file
FILE* fptr2 = fopen(FileName, "w");
fclose(fptr2);
// continue reading
fptr = fopen(FileName, "r");
}
char firstLetter;
int headerExists = 0;
if(!feof( fptr ))
{
fscanf(fptr, "%c", firstLetter);
if(firstLetter == 'I')
headerExists = 1;
}
fclose(fptr);
FILE* fptr2 = fopen(FileName, "a");
if(!headerExists)
fprintf(fptr2, "ID FIRSTNAME LASTNAME");
for(int i = 0; i < EMPS; i++)
fprintf(fptr2, "\n%d %s %s", e[i].id, e[i].firstname, e[i].lastname);
fclose(fptr2);
}
[ Code originally at http://pastebin.com/tLefJhEH ]
The problem probably lies at the fscanf(fptr, "%c", firstLetter);
. %c expects a char* as input while you are giving it a char (which is an integer in c).
To fix it try fscanf(fptr, "%c", &firstLetter);
Also calling fclose on a null pointer is not recommended.
My mistake, it's this line:
68. fscanf(fptr, "%c", firstLetter);
Should be:
68. fscanf(fptr, "%c", &firstLetter);
Argments to fscanf
and scanf
are addresses of the memory locations to store the data.
You don't need the &
for a string because a string is already an address.
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