How to open a file with a user inputted variable in C? - c

Question

I'm writing a POS program as a school assignment. I'm using multiple txt files as a database. The program is suppose to allow the user to enter a SKU number (e.g. 123) then it will open a txt file in a database (e.g. database/123.txt). It then pull info from the txt file such as a price and allow the user to add multiple files and end with a total. The user can also add to the database by creating new SKUs. They are also able to view transaction history. The issue I am having is I can't seem to figure out how to record a number from a user and then use that number to open a text file beginning with that number. (e.g. use enters 123 then 123.txt is opened.)
Here is the section of my code that I need help with:
// Function to start a transaction
int transaction(void)
{
// Define Variables
char buf[1000], nDatabase[100];
float nPrice[500], nTotal;
// Instructions
printf("You have started a transaction.\n");
printf("Enter the SKU number below.\n");
printf("Enter 0 to complete the transaction.\n");
// Begin loop here
do
{
FILE *ptr_file;
// record SKU number
/*remove test tools later*/
printf("we r here\n");
scanf("Enter the SKU: %c\n", &nDatabase);
printf("now we r here\n");
// Open database file
/*Change location later*/
ptr_file = fopen("database/123.txt", "r");
// If file is not found return 1
if (!ptr_file)
{
printf("Could not match that SKU number.\n");
return 1;
}
while (fgets(buf, 1000, ptr_file) != NULL)
printf("%s\n", buf);
scanf("%s", &nPrice[0]);
// Close file
fclose(ptr_file);
while (nDatabase == 0);
nTotal = nPrice[0] + nPrice[1];
printf("Your total is: $%.2f\n", &nTotal);
return 0;
}
}

Answer 1

printf( "Enter the SKU: " ) ; // <-- scanf if only for input, the prompt must be output separately
scanf( "%s\n", nDatabase);
// ^ ^
// | |_No & here - nDatabase is an array
// |
// |_Accept a string not a character
Then you might form a complete file name with sprintf, e.g.
char filename[MAX_FNAME] ;
sprintf( filename, "database/%s,txt", nDatabase ) ;
Be aware that no error checking or overrun protection is performed by the above - you may want to consider adding some.

Answer 2

You need to concatenate the user input with you database path, and extension.
Check this post: C string append