Thread: Deleting a line from a file

I have a program that is supposed to delete records from a file, I tried opening the file to read and write and using fgets to input each line. I'd then sscanf the input to a string and test to see if one of the items in the line is the record. If it is then I use continue to skip it and if it isn't then I fputs the line back into the file.

Supposedly this should leave the file as it was except without the one line I wanted to delete, but it's not working at all. Here's the code

Code:

int delete_rec()
{
	FILE*fpt;
	unsigned long number;
	char buffer[500],
		 pInput[500];
	struct cust TEMP;

	printf("\nDELETE RECORD");

	if(!(fpt=fopen("cust.dat","rw"))){
		printf("Error opening cust.dat for delete");
		return (1);
	}

	printf("\nCustomer Number:");
	scanf("%d", &number);
	fflush(stdin);
	
	while(fgets(buffer, sizeof(buffer), fpt) != NULL){
		sscanf(pInput, "%d%*c%49[^;]%*c%49[^;]%*[^OoSs]%c", &TEMP.no, TEMP.name, 
			TEMP.add, &TEMP.status);
		if(TEMP.no == number)
			continue;
		fputs(buffer, fpt);
	}

	if(fclose(fpt) == EOF){
		printf("Error closing file\a\n");
		return 1;
	}
	printf("\n\nDeleted. Press ENTER to continue.\n");
	getchar();

	return 0;
}

Update:
I found a problem with the loop, but it still doesn't work, here's the change.

Code:

	while(fgets(buffer, sizeof(buffer), fpt) != NULL){
		strncpy(pInput, buffer, 500);
		sscanf(pInput, "%d%*c%49[^;]%*c%49[^;]%*[^OoSs]%c", &TEMP.no, TEMP.name, 
			TEMP.add, &TEMP.status);
		if(TEMP.no == number){
			;
		}else{
			fputs(buffer, fpt);
		}
	}

It's very hard to modify a text file like this, because line lengths can change.

It's much simpler to simply create another file with all the changes, then do a delete/rename when you're done.