I am trying to take input from stdin and along with that i would like user an interactive output through fscanf. I used fscanf as given in example but it does not print anything and always returns an error that leads to execution of fprintf().


#include "stdio.h"

int main(int argc, char* argv[])
{
int height, width;
if ( fscanf( stdin, "Height: %i, Width: %i", &height, &width ) != 2 )
{
fprintf( stderr, "###Error with fscanf: bad input data.\a\n" );
return 0;
}

printf("Height %d, Width %d\n", height, width);
return 0;
}


Thanks in advance

1.try using #include <stdio.h> instead of #include "stdio.h"

2.you expect having two int values in stdin, but your stdin is empty...

fscanf( stdin, "Height: %i, Width: %i", &height, &width )

you have no input!

See what fscanf does: http://www.cplusplus.com/reference/cstdio/fscanf/

3. fprintf( stderr, "###Error with fscanf: bad input data.\a\n" ); always executes because your program fails to read a string (char*) from stdin wih format "Height: %i, Width: %i".

-------------

See this example:
(It works because now you have something in stdin, but also, there is no input)

-------------
---------------

the safest way of reading something from keyboard is:
1. declare a char array
char buffer[256];
2. use fgets to copy everything from stdin to buffer (Important: stdin must be empty if you want this function to ask you to type a string. If the stdin is not empty, then it will take what is already in stdin).
fgets(stdin,256,buffer);
3. use sscanf function to read your variables from the char array (in this case buffer)
sscanf(buffer,"%d %d",&height,&width);

---------------

Or you can simply use scanf...

> I used fscanf as given in example but it does not print anything

Nobody stated it would ever print anything. That's what (f)printf does.

And please use &#91;code] and &#91;/code] tags if you paste code.

what example? my example?
fprintf will print, and you will see that if you print on stderr or stdout.
fscanf does not print anything but fprintf does...

------------

Now I see I was wrong...

Just type something like: "Height: %i, Width: %i" and it will work.

fscanf will ask you for an input when you try to read from stdin.

The only mistake OP did was #include <stdio.h>

if fscanf and scanf do not print strings (Height and Width given in code) then what is the use of these strings in fscanf and scanf functions.

Basically nothing, leave them out:
(Except if you had an input file containing lines like this:
Height: 32, Width: 40
Height: 40, Width: 1
...)

the meaning is to parse the input text:
using: fscanf( stdin, "Height: %i, Width: %i", &height, &width ) and typing "this:34 and that: 56" will do nothing, but entering Height: 44, Width: 33 will find two integers.
try to check it

1 members found this post helpful.

Thanks for clearing doubt. It really helped me to understand the exact functionality of fscanf & scanf.