The .txt does not correctly edit the text - C - c

Question

I'm having a problem with the .txt as I have to create a customer record and then I can change the data. What happens is the following, when I create the client the data looks like this:
enter image description here
But when I go to edit the name or the country, it's like that, and what I wanted is for you to make the change without creating new lines.
Name:
enter image description here
Country:
enter image description here
I'm probably missing something or it's the way to save the file, but I don't know!!
This is my code:
typedef struct {
char name[80];
char country[10];
int tin;
int customer_code;
} CLIENT, upd, add;
void
edit_customer()
{
CLIENT add, upd;
int choice;
FILE *bd;
bd = fopen("bd.txt", "a");
printf("Enter the customer code: ");
scanf("%d", &add.customer_code);
printf("\nSelect the type of change you want:\n1 - Name\n2 - Country\n\nEnter your choice:");
scanf("%d", &choice);
switch (choice) {
case 1:
fgets(upd.name, 80, stdin);
printf("Type your name: ");
scanf("%[^\n]s", upd.name);
fprintf(bd, "code: %d | name: %s | tin: %d | country: %s \n",
add.customer_code, upd.name, add.tin, add.country);
printf("Changes saved!");
break;
case 2:
printf("Enter the Country:");
scanf("%s", upd.country);
fprintf(bd, "code: %d | name: %s | tin: %i | country: %s \n",
add.customer_code, add.name, add.tin, upd.country);
printf("Changes saved!");
break;
}
}

Answer 1

Updating the data in a file is not easy. First of all you have to decide how you intend to save your data because the way you modify the data will depend on this. There are many ways to do this but to keep it simple there are two basic ways. The first way is to insert records of fixed size. practically you have to decide the size of each field of your record and it will always have to be the same for all the records of your file. So, taking your struct as example
typedef struct {
char name[80];
char country[10];
int tin;
int customer_code;
} CLIENT;
you could write the records by modifying the formatting of the fprintf a little, for example in this way:
"| code: %-10u | name: %-20.20s | tin: %-10u | country: %-25.25s |\n"
this way your file will contain records like this (knowing their position in the record you wouldn't really need the name of the fields):
| code: 1234561 | name: Super Mario | tin: 1286608618 | country: know the name |
| code: 23 | name: John | tin: 123 | country: Donknow |
now if you want to modify one of the records present, you will have to search for it in your file by reading line by line and saving, before each reading, where the line begins in your file using for example the ftell function. Found the record, load its fields and modify those you want to change and at this point move the file pointer back to the beginning of the line (fseek function) and overwrite the old record with the one just modified.
If, on the other hand, you do not want to use fixed-size records, as you are doing now, the work becomes a little more complicated because unfortunately the files are not elasticized, so if you need to modify a record that has a different length than the one in the file you have to make room for it. There are a thousand ways to do this but in essence you should:
save the records that are under the one you want to modify in the file
modify the record
cut the file at the end of the record you edited
append the part you previously saved to the file
In truth for safety you should:
create a temporary file
copy the records preceding the one to be modified into the temporary file
append the new record
append the remainder of the file except the old record
save the temporary file (fclose)
delete the old file
rename the temporary file with the name of the file just deleted
Apart from that, as the comments say, in your program you try to modify a record that you have not read from the file, so the one modified by the user is the only field that has a value while the others have not been initialized. However, it is not enough. You will have to follow what I have written to you if you want to see your program work.