Thread: problems with fgets

1) fflush(stdin) doesn't work, for the same reason flushing your kitchen faucet won't work - it's not the toilet, and is an input stream, not an output stream.

2) I don't see anything wrong with your use of fgets(), but obviously the char array must be properly sized, including the end of string char (and probably the newline char as well).

code to remove the newline char, is generally:

Code:

len = strlen(charArrayName);
if(charArrayName[len-1]=='\n')
  charArrayName[len-1]='\0';

To stop the "jumping" over your fgets(), add this:
getchar(); //pull one newline off the input buffer

after each scanf() line of code. Obviously, fflush(stdin) isn't working, and *c in scanf() isn't pulling off the newline char as you'd like, either. That's what's causing the "jumping".

Give that a shot.

Thanks for the tips.

Just to make clear.

Your advice is use fgets to get strings and sscanf to get the float value of price?

Yes, sscanf() and fgets make a lovely couple dancing together.

Originally Posted by Adak

1) fflush(stdin) doesn't work, for the same reason flushing your kitchen faucet won't work - it's not the toilet, and is an input stream, not an output stream.

2) I don't see anything wrong with your use of fgets(), but obviously the char array must be properly sized, including the end of string char (and probably the newline char as well).

code to remove the newline char, is generally:

Code:

len = strlen(charArrayName);
if(charArrayName[len-1]=='\n')
  charArrayName[len-1]='\0';

To stop the "jumping" over your fgets(), add this:
getchar(); //pull one newline off the input buffer

after each scanf() line of code. Obviously, fflush(stdin) isn't working, and *c in scanf() isn't pulling off the newline char as you'd like, either. That's what's causing the "jumping".



Give that a shot.

So, remove all fflush.
Create a dump_line function and call it after fgets?

Ok. I'll try a mix of the advices to get a nice solution.

My program is full funtional. But the "basic things" don't work. This is make me mad

Or I don't understand or something is missing.
I change my code to this,

Code:

printf("Create a new component\n");
			do {
				printf("Serial number?\n");

				fgets(c_description, STR_SERIAL, stdin);
				getchar();
				validStringSize = verifyStrLengh(c_serial_number, STR_SERIAL);
			} while ((indexof(c, n_elems, c_serial_number) != -1)
					|| (validStringSize != -1));

			do {
				printf("Components' name\n");
		
				fgets(c_description, STR_NAME, stdin);
				getchar();
				validStringSize = verifyStrLengh(c_name, STR_NAME);
			} while (validStringSize != -1);


			do {
				printf("Components description\n");
	
				fgets(c_description, STR_DESCRIPTION, stdin);
				getchar();
	

				validStringSize
						= verifyStrLengh(c_description, STR_DESCRIPTION);
			} while (validStringSize != -1);

			do {
				printf("Price\n");

				validValue=sscanf(stdin,"%f",&price);
				

				if (validValue == 0) {
					printf(
							"You inserted a invalid character, use numbers please\n");

				}
				if ((validValue == 1) && (price <= 0)) {
					printf("Insert a positive value to price, please\n");
				}

			} while ((validValue != 1) || (price <= 0));

			if (insertComponent(c, &n_elems, c_serial_number, price, c_name,
					c_description)) {
				printf("Component successfully inserted\n");
			} else {
				printErrorMessage("Insertion unsuccessful\n");
			}
			getchar();//scanf("%*c");
			break;

and cycle infinite in price.

Doesn't work If write a bigger string then STR_SERIAL, program don't stop

Code:

		case 1:
			printf("Create a new component\n");
			do {
				printf("Serial number?\n");
		
				fgets(buff,sizeof buff,stdin);
		
				getchar();
				validStringSize = verifyStrLengh(buff, STR_SERIAL);
				if(validStringSize) {strcpy(c_serial_number,buff);}
			} while ((indexof(c, n_elems, c_serial_number) != -1)
					|| (validStringSize != -1));

without getchar(); jumps.
and verifyStrLengh is defined

Code:

int verifyStrLengh(char *str, int max_size) {
	int excedeed = -1;
	int aux;
	aux = strlen(str);
	if (aux > max_size) {
		excedeed = 1;
		printf("Max string size is %d, insert again please\n", max_size);
	}
	return excedeed;
}

Code:

validValue=sscanf(stdin,"%f",&price);

This doesn't work, since sscanf() uses what's in the buffer (stdin in this case), AT THAT MOMENT.

Which is nothing.

Stick with the good combo:

Code:

printf("Enter the price, in digits: ");
fgets(c_description, STR_DESCRIPTION, stdin);
sscanf(c_description, "%f", &price);

//etc.

Since you're giving fgets() the base address of c_description (which is it's name), the first part of the c_description will be over-written by the price data.

So, you need to either:

1) handle the data in c_description before you use fgets() again, or
2) create some other char arrays, just for price, etc.

With fgets(), you don't need any getchar() afterward, to help clean the input stream. It will confuse the user since the getchar() will wait for something to be in the input stream (it is buffered).

It's either: scanf() with getchar() afterward, or fgets() with no getchar() afterward. Not both.

Try and keep your string handling as simple, and straight forward (easy to understand), as possible. And remember, that only char's with the end of string char on the end ('\0'), are strings. Char's without the end of string marker char, are just a bunch of char's - not a string.

Sometimes, a bunch of char's is just what you want for a program. Most times, it is definitely not what you want, however.