Thread: Sscanf modifing another value

Hi!, i'm new with c, sorry if it's a newbie question, but i can't find an answer.

I have some Ints declared, and after that I am using a sscanf (with some buffers), but sscanf is modifing the previously declared ints, why that is happening?
Here is my code:

Code:

...
        int xivn=0;  //here i declare the ints (i never modify this values)
	int xivt=0;
	int xiv=0;
	int xivf=0;
	
	if (archivo!= NULL){
		char linea [128];
		char resto0 [20];
		char resto1 [20];
		char resto2 [20];
		while (fgets(linea,sizeof(linea),archivo)!=NULL){
			sscanf(linea,"%s %s %s %s", c0, resto0, resto1, resto2); //if i comment this line i can see the values of the ints unmodified  
		}
		fclose(archivo);
	}else{
		perror(nombrearchivo);
		return 1;
	}
	printf("xivn:%d, xivt:%d, xiv:%d, xivf:%d \n\n",xivn,xivt,xiv,xivf); //it prints xivn:0, xivt:47, xiv:1919221868, xivf:1953326451  :(

I'll really appreciate if someone can help me.
Thank you!

Code:

sscanf(linea,"%s %s %s %s", c0, resto0, resto1, resto2);

Did you forget c0?

Hi Adak, thank you for your response!,
i forgot to paste it here, but it's in my code:

char c0[2];
FILE *archivo = fopen (namefile,"r");

I like using a slightly different syntax for this fgets line of code, but I'm not confident that's the problem here. Give it a try:

Code:

while (fgets(linea,sizeof(linea),archivo)!=NULL){
    sscanf(linea,"%s %s %s %s", c0, resto0, resto1, resto2); //  
}        
//change that to:
while ((fgets(linea,sizeof(linea),archivo))!=NULL){
    sscanf(linea,"%s %s %s %s", c0, resto0, resto1, resto2); //
}

And double check that your string variables are long enough to handle the size of the strings you're handling, including the end of string markere: '\0', which you can't normally see, but have to allow space for.

After that, I'd have to run the code to see what's up.

nop, the same problem

It's a small version but with the problem:

Code:

#include <stdio.h>
#include <string.h>
int main(int argc, char* argv[]){
	char c0[2];
	FILE *archivo = fopen ("teapot_uv.obj","r");
	int xivn=0;
	int xivt=0;
	int xiv=0;
	int xivf=0;	
	if (archivo!= NULL){
		char linea [128];
		char resto0 [20];
		char resto1 [20];
		char resto2 [20];
		while ((fgets(linea,sizeof(linea),archivo))!=NULL){
			sscanf(linea,"%s %s %s %s", c0, resto0, resto1, resto2);
		}
		fclose(archivo);
	}else{
		perror("teapot_uv.obj");
		return 1;
	}
	printf("xivn:%d, xivt:%d, xiv:%d, xivf:%d \n\n",xivn,xivt,xiv,xivf);
	return 0;
}

Thank you for your patience!

Yes, there are comments, my idea is to "pass" that comments using c[0]!='#';

In the data, c[] becomes "vt". Since c is only sized for two char's, it can't fit the end of string char. Also, there are several places in the header where the arrays are running out of bounds.

The program runs on, in that early part, but it's entirely lucky. What I've done in the past is just what you mention - if linea[0] == '#' then don't sscanf() that line.

Do that, and make c[] 3 or 4 char's, and that should help a lot.

I just ran through the data, and c[3] works OK with the file you provided, once you add the

Code:

if(linea[0] != '#') {
  sscanf() all in here

code.

Problem solved, Thank you Adak and Salem!!!!!!!!