Thread: proble with string

Hello everyone. I am having a trouble with storing first and last names into the string, the program stops after it asks to type the first name in.

here is the function

Code:

struct student get_student_number_and_name(struct student X[MAX], int y)
{
	int i, valid, num;
			
	for(i=1; i<=y; ++i)
	{
	
		do{
			valid=0;
			printf("\n\nEnter student %i - #  ", i);
			scanf_s("%i", &num);

				if(X[i].student_num==0)
				{
					X[i].student_num=num;

					printf("First name:  ");
					scanf_s("%s", X[i].first_name); //it stops here.
					printf("Last name:   ");
					scanf_s("%s", X[i].last_name);
				}
				else
				{
					printf("Student Number has been entered! Try agin!");	
					valid=1;
				}
		}while(valid!=0);

	
	
	}
	return X[MAX];
}

I do no see why it stops. I will be very ppriciated if anyone can point where I am wrong.

Thank you.

Code:

    (struct student X[MAX], int y)

is equal to

Code:

    (struct student *X, int y)

write struct student here

and

Code:

    return X[MAX];

change to

Code:

    return X;

X - will be pointer, so define the function as struct student *get_student_number_and_name(

by returning he can control the function (know how it is work), if he return a pointer - it's ok, if he return NULL - something wrong, so he can check the validity of the array or scanf result (there are many moments)

Thanks, finaly it works .

Originally Posted by Salem

> I do no see why it stops. I will be very ppriciated if anyone can point where I am wrong.

> scanf_s("%s", X[i].first_name); //it stops here.
Well you're wrong in that you didn't read the manual for scanf_s before using it.
scanf_s, _scanf_s_l, wscanf_s, _wscanf_s_l (CRT)
%s needs a buffer size, and you're just passing garbage with the non-existant parameter.

And Microsoft was wrong in believing that anyone who used the non-portable and proprietary _s versions of standard library functions would be able to write better code. Especially since they didn't bother to make the compiler diagnose printf/scanf screwups.

scanf_s is no more safe than scanf, if you DON'T read the manual on how to use it properly.

Salem I see that now, I used scanf_s because my compiler giving me a warnings all the time when I am using scanf, guess I just have to ignore it.

> for(i=1; i<=y; ++i)
Lemme guess, you want to fill an array.
Arrays start at 0, not 1.
The typical array subscripting loop is
for( i = 0 ; i < y ; ++i)

That's the way my teacher'd like us to do, and I do not agree with it also, as on my thought everything has to be done in a right way from a very beginning of our learning process, but for now I have to follow her rule.

Thanks for all your replies.

quzah,

Code:

    scanf_s("%s", X[i].first_name);

if he will repair it to right form, what he will get if the function will not save the entered data ?
(it shouldn't return void)
maybe int or pointer to start array, but not void, because if he will lose data he will must check all array for this state (lost or not) after every call of the function

Originally Posted by Salem

> I used scanf_s because my compiler giving me a warnings all the time when I am using scanf
More manual reading perhaps?
Security Enhancements in the CRT

Your sarcasm drove me to read that( mannual ) and think now I do understand those kind of things better , thank you.

quzah,

Code:

        printf( "Enter a number: " );
        fflush( stdout );
        scanf( "%d", &bar[ x ] );

no, push ctrl+z at first element (or send a file to the input of the program with three numbers by command "type file.txt | prog.exe")
you will get output like 1 2 3 at new line every
how do you know how many numbers in the file ?
how do you know there are 1 2 3 and not 1 2 3 0 0 ?

if I would write this function, I would have not only a check for scanf() == 1 (and returning EOF if it is not save the data), but else function would return number of writed elements to the array (and I would know how many elements it has saved)

in your example you can't know what was there (input with zeroes or incorrect input)

why you use fflush( stdout ); I don't know, what wil be without it ? (it is only flushes the buffer, when stdout use buferization of characters before output)

Originally Posted by quzah

There is no guarantee that you will ever see the output of printf if you aren't outputting a newline.

newline is a character, where have you known that ?

Originally Posted by quzah

It was to illustrate the point that the array is going to be changed by my function (or not, I could write it to not change it), and that returning the array would be completely irrelevant.

If I will input letters your array will not change and function will not return info about such situation (and your loop after it will print array)
I would write a function which when get a letter return and loop wouldn't run or it run for only entered data (without printing of empty values)

Originally Posted by quzah

Furthermore, sending EOF to break his error checking still isn't going to make returning something any different. It doesn't matter.

it has very much matter if you have over 10 functions and more (because you can control every step of your program), and if you don't know what happen at every step, you may seed the bug which will be hided for months

Originally Posted by quzah

Sending EOF to the function is completely irrelevant with regards to the function's return value.

Sending EOF to scanf means only when the input is end, your function continues save values, but it must return an info about this situation (with continue or stop of entering)

but your loop has such header

Code:

    for( x = 0; x < baz; x++ )