Error check (files) - c

Question

How can I implement an error check that will loop until a code within a file is entered? This is what I have so far: I have already store each code from the file in an array called array[j].code1.
Here:
printf("Enter item code: "); //Prompts user
scanf ("%14s", codenew1); //Read user input
len = strlen(codenew1); //Read each character into variable len
while (len != strspn(codenew1, "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"))
{
printf ("Name contains non-alphabet characters. Try again!: "); //Prompts user to try again
scanf ("%14s", codenew1); //Reads user input
len = strlen(codenew1); //Read each character into variable len
} //Endwhile
strncpy(codenew, codenew1,2); //Copy the first two characters from the variable codenew1
codenew[2] = 0; //Store first two characters into variavle codenew
for ( j = 0; j < num_items; j++) //Loop for num_items times
{ //Beginning of for loop
if (strcmp(array[j].code1, codenew) == 0) //If codenew is found in file
{ //Beginning of if statement
price[i] = item_qty[i] * array[j].price1; //Calculating the price of an item
printf("Price : %d", price[i]); //Prints price
printf("\nEnter '%s' to confirm: ", array[j].itemname1); //Confirming the item
scanf("%19s", item_name1[i]);
while (strcmp(item_name1[i], array[j].itemname1 )!=0) //Looping until both item names are the same
{ //Begin while loop
printf("Item name is not %s ,Try Again!: ", array[j].itemname1); //Prompt user to try again
scanf ("%19s", item_name1[i]); //Reads item name into an array
len = strlen(item_name1[i]); //Reads each character into variable len
} //End while loop
len = strlen(item_name1[i]); //Read each character into variable len
while (len != strspn(item_name1[i], "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz")) //While len contains non alphabetic characters
{ //Beginning while
printf ("Name contains non-alphabet characters. Try again!: "); //Prompts user to try again
scanf ("%19s", item_name1[i]); //Read user input
len = strlen(item_name1[i]); //Read each character into variable len
} //End while
strncpy(item_name[i], item_name1[i], 20); //Copy the first two characters from the variable codenew1
item_name[i][20] = 0; //Store first 20 characters in variable item_name[i]
total_price+= price[i]; //Calculate total price
break; //Terminates loop
} //End of if statement
else
if (strcmp(array[j].code1, codenew) != 0) //If codenew is found in file
{
printf("Invalid input! Try again.");
goto Here;
}
} //End of for loop

Answer 1

The current structure of the code is
Here:
// get "codenew" from user
for ( j = 0; j < num_items; j++ )
{
if ( strcmp(array[j].code1, codenew) == 0) )
{
// do a whole bunch of stuff
break;
}
else if ( strcmp(array[j].code1, codenew != 0) )
{
printf( "Invalid input! Try again.\n" );
goto Here;
}
}
The behavior of the code is to check the first entry in a list of codes. If the first entry matches the user input, then "whole bunch of stuff" gets executed and the loop breaks. Otherwise, an error message gets printed and the code jumps back to the label Here:. Thus, the user is forced to enter the first code in the list. Any other code just jumps back to the beginning.
I assume that what the code should do is scan the whole list to see if it can find a matching entry. To accomplish that, I would put the code into a subroutine that searches the list and returns 1 if it finds a match, or 0 if no match is found. The function would be called repeatedly until the user enters a valid code. Here's the structure of the proposed function.
int findCode( void )
{
// get "codenew" from user
for ( j = 0; j < num_items; j++ )
{
if ( strcmp(array[j].code1, codenew) == 0) )
{
// do a whole bunch of stuff
return 1; // SUCCESS, the user entered a valid code
}
}
return 0; // FAILED, no matching code in the list
}
Here's how the function would be called. The while loop will keep calling the function until it returns "success".
while ( !findCode() )
printf( "Invalid input! Try again.\n" );