Thread: Flexibility with reading one or two strings?

You could read up on how scanf works, or you could read a whole block with fgets; the things your book or lesson should have or should be covering right about now.


Quzah.

Using fgets followed by sscanf is a good idea, because then you can use #defines for your buffer sizes instead of magic numbers.

C doesn't have native regular expression support, so the usual way to specifify at each point what you expect next. How should the program know where the end of the name is? You seem to want to allow having a line with nothing in the name field, instead the age field immediately follows, but how would your program know that the person's first or last name is not "age"?

Originally Posted by bungkai

Well, as I said above, I've already tried fgets() but it does not prompt for an input.

What are you even trying to say here? fgets just takes a block/line of input, you still have to put something like "printf( "Enter a line: ");", that's not built into fgets. Besides, you saying fgets doesn't work tells me nothing - and since I've used fgets successfully in the past, leads me to believe that you don't know what you are talking about. Which is why you should be posting your example of it not working.


Quzah.

Just replace your first scanf() with an fgets statement into a temp buffer. Then store the value into your structure. Take a look at how to get a line of text.


EDIT: You don't need to use a temp buffer btw. Just threw it out there.

Then it is something that you are doing wrong in your code. Here is a short example code:

Code:

#include <stdlib.h>
#include <stdio.h>

typedef struct{
	char name[20];
}myStruct;

int main(void){

	myStruct example;

	printf("Enter your name:");
	fgets(example.name,sizeof(example.name),stdin);

	printf("%s", example.name);
	getchar();
	return (0);
}

It is possible that you have a trailing newline char in your buffer from some previous input operation. Did you ask the user for anything else prior to this?

Originally Posted by bungkai

char buff[20];
fgets(buff, sizeof(buff), stdin);

I don't think there's anything wrong here, but I can't seem to get it working

quzah: sorry for my lack of clarity, I meant take in an input. Not prompt.

I didn't mean just show me how fgets works, I already know how it works. I meant post your actual program that you are having problems with. The whole thing, and your sample file you are trying to read.


Quzah.

Ok, so you have this:

Code:

while((scanf("%s", &c)) != EOF)

Although you declared c to be a character, not a string. This may lead to problems. The newline character is still in the buffer from your scanf call. You need to deal with that before you try to take anymore input using fgets because fgets will stop at the newline character.

You should check the return of malloc, plus there is no need to cast it.

Try to reorganize your code so you you do not need global variables, these will tend to lead to all sorts of bad behavior.

Ok, so the "%s" tells scanf you want a string input. You want the "%c" which means character. The extra newline is in there because the first scanf() call only takes the 'n' (for example) out of the buffer but leaves the '\n' (user hitting enter) in the buffer. So:

Code:

while((scanf("%c", &c)) != EOF)
{
      getchar();
      if(c == .....

Give that a shot.

%s in scanf stops on whitespace, but does not read the whitespace, leaving it waiting for whatever you read next. Therefore, when you call fgets next, it immediately sees the newline, and pulls it off of the input stream, because that's what fgets does. You should generally pick one method for taking input, and use it the whole way through. If you want to use scanf then do so everywhere, and if you want to use fgets then use that everywhere.

The problem is that after you ask it for a letter or a word, they hit enter, and you ignore the fact that they have it enter, and then wonder why it's skipping the next prompt you have. Like I said the first time, you should read up on scanf and fgets, and pick one, and use that. Just randomly throwing different pieces in and hoping they magically fix it isn't usually a good idea. It's best to know why something does or doesn't work.


Quzah.