My C code is acting strange

[aldreneo]

What I want the code to output(red is stuff I typed blue is stuff the computer outputted):
>test
test
>test with spaces
test with spaces
>

code:

#include<stdio.h> main( ) {  int loop;  while(loop>=0)  {   char i;    printf( ">" );    scanf( "%s", &i );    printf( "%s \n", &i );  } }

But this is what I get as an output (Stuff in red is what I typed stuff in blue is what the computer outputted):
>test
test
>test with spaces
test
>with
>spaces
>


Gcc latest

[Tony]

is this a joke? how familiar are you with C?

[aldreneo]

Not much....more used to c++ why? is it something stupid?

[Tony]

I don't think you know C++ well ether..

#include<stdio.h>

main( )
{
int loop; <- uninitialized variable, no assigned value
while(loop>=0) <- comparing random memory location against 0.

// how about while(true) for an infinite loop?

{
char i; <- declaring a character
printf( ">" );
scanf( "%s", &i ); <- reading a character string into character
printf( "%s \n", &i );
}
}


%s ends by whitespace (space, newline, etc)

you're probably looking for gets()

[aldreneo]

That was stupid of me...
Updated source works...

code:

#include<stdio.h> main( ) {  int loop;  while(loop>=0)  {    char i;    printf( ">" );    gets( &i );    printf( "%s \n",&i );  } }

[/code]

[rizzix]

That code is not safe.

[aldreneo]

How?

[Tony]

let me try to explain it to you again

Tony wrote:

char i; <- declaring a character

scanf( "%s", &i ); <- reading a character string into character

Now you're reading an entire line.

Guess what - a line is much bigger than a character, so

- you locate 2 empty bytes of space in your memory
- you fill those 2 bytes, and up to 254 bytes after (is there a limit on gets?). All but the first 2 bytes are not neccessarely free, so you end up writing over abstract memory location.

Oh, and it's an infinite loop, so you're doing this over and over and over again. Do it enough, and watch your system start acting up funny and die.

[md]

You are still using an unitialized int for running through your loop (int loop); nad your reading a string in and and trying to store it in a character. I would sugest reading some more about C (and C++ for that matter), as these are serious errors.

[Martin]

Guys, can we be a little less hostile and a little more friendly please?

[md]

Ok, here is your Code

C:

#include<stdio.h> main( ) {     int loop;     while(loop>=0)     {         char i;         printf( ">" );         gets( &i );         printf( "%s \n",&i );     } }

Here is one possible way of writing it would be (that is proper)

C:

#include<stdio.h> main( ) {     int loop = 0;     while(loop>=0)     {         char buffer[256];         printf( ">" );         gets( &buffer );         printf( "%s \n",&buffer );     } }

Notice how the variable loop is initialized to be 0 before it's used? If you don't initialize a varaible then it's value is undefined (it could be anything). Also note that buffer is an array of characters. In C char is a single character, whereas strings are stored as a null-terminated array of characters.

[rizzix]

That too, is not safe. What happens if the user enters 256 or more characters?

Simply put: gets is unsafe by design. Don't use it in this manner (i.e. to get strings).