Saving files into a structure - c

Question

I've got a program in which I would like to read and save data into. Ideally I would like to read the data, be able to display and make changes to the data, and then be able to save it back onto another file if needed. Right now I have it to where I can read the data, but I can't make changes or save the content to another file. I'll spare you from posting my entire code, since it's rather lengthy, but here is my structure, main function, menu function and read function.
typedef struct friends_contact{
char *First_Name;
char *Last_Name;
char *home;
char *cell;
}fr;
int main() {
fr friends[5];
char buffer[BUFFSIZE];
int counter=0;
int i=0;
menu(friends, &counter,i,buffer);
getch();
return 0;
}
//Menu function
void menu(fr*friends,int* counter, int i,char buffer[]) {
int user_entry=0;
int user_entry1=0;
int user_entry2=0;
char user_entry3[50]={'\0'};
FILE *read;
printf("Welcome! Would you like to import a file? (1)Yes or (2) No");
scanf("%d",&user_entry1);
if(user_entry1==1)
{
printf("Please enter a file name");
scanf("%s",user_entry3);
read=fopen(user_entry3,"r");
}else;
do{
int result;
printf("\nPhone Book Application\n");
printf("1) Add friend\n2) Delete friend\n3) Show a friend\n4) Show phonebook\n5)Exit\n");
scanf("%d", &user_entry);
if(user_entry==1)
{
add_contact(friends,counter,i,buffer);
}
if(user_entry==2)
{
delete_contact(friends ,counter,i);
}
if(user_entry==3)
{
result=show_contact(friends ,counter,i);
if(result==0)
{
printf("\nName not Found\n");
}else
result;
}
if(user_entry==4)
{
print_contact(friends, counter,i,user_entry3);
if(user_entry1==1){
file2(friends ,counter,i,buffer,read);
}else;
}
}while(user_entry!=5);
if(user_entry==5)
{
fclose(read);
printf("Would you like to save entries to a file? (1)yes or (2) no");
scanf("%d",&user_entry2);
if(user_entry2 == 1)
{
printf("Please name your file");
scanf("%s",user_entry3);
file(friends, counter,i,user_entry3);
printf("Goodbye!");
}else if(user_entry2 == 2)
{
printf("Goodbye!");
}
}
}
My read function:
char file2(fr*friends ,int* counter, int i,char buffer[],FILE*read){
fseek(read, 0, SEEK_SET);
while (fscanf(read, "%s", buffer) != EOF)
{
friends[i].First_Name=malloc(BUFFSIZE*strlen(buffer));
strcpy(friends[i].First_Name, buffer);
printf("%s\n",friends[i].First_Name);
}
}
As I said, right now I can view the contents of the file, but I cannot edit them or even output them to another file. There are also probably things in my code that are not perfect, but I'm trying to focus on this before i worry about making other changes( Since the program works outside of the issue mentioned). I'm ready to give out a big green checkmark! :)

Answer 1

If you want to edit the strings in your application, bear in mind, that you will have to take care of growing the buffer when needed. It might be more reasonable to use a fixed length records (and padding the string with zeros). Then you could only check that you are not overflowing past theend of the buffer and use fread() and fwrite() to read/dump the fr structures from/to a file in one go (basically read/write sizeof(fr) - unless you run the application on machines with different endianessess it's safe).
That said, a couple of obsrvations:
use switch instead of multiple if(user_entry==x), do something in the else part (print warning or whatever) - it usually signals either a regular or an error branch in the code.
use width in fscanf(read, "%s", buffer), to specify maximum string length that can fit in buffer, remember, that the '\0' string terminator is not counted towards this, so you need to use size of buffer - 1. I.e. either hardcode it to e.g.: %50s or compile the correct format string at runtime.
malloc(BUFFSIZE*strlen(buffer)) is probably not the size you really want to allocate
always check malloc() return value!