CODEWITHSUNDEEP
csegmentation-faultfgets
SystemFun
SystemFun

Reputation: 1072

c segmentation fault fgets

int main( int argc, char** argv) {

        FILE *inFilePtr = fopen(*(argv + 1), "r");
        char *rawdata = malloc(sizeof(char) * 100);
        float *ary = malloc(sizeof(float) * 50);
        int counter = 0;
        float averageAns;
        int count = 0;


        while (count < 1 ){
            //fgets(rawdata, 50, inFilePtr); //I have tried both
            fscanf(inFilePtr, "%s", rawdata);
            *(ary + counter) = atof(strtok(rawdata, ","));
             counter++;
            *(ary + counter ) = atof(strtok(rawdata, NULL));
            counter++;
            *(ary + counter) = atof(strtok(rawdata, NULL));
             counter++;
            count++;
        }

I cannot for the life of me figure out why I keep getting a seg fault. It will seg fault even without the loop (the count < 1 was just to see if I could make it through once).

It will not work with fgets(), fscanf(). It seg faults when I change the stream in fgets to (stdin), and I mention this because I assumed the file * was the issue, but now I do not think it is. I have made the delimiter in my data file " " and ",".

If anyone know's what I did wrong, I would appreciate it.

Upvotes: 1

Views: 544

Answers (2)

Rico
Rico

Reputation: 11

Try casting your malloc calls with (char *)

maybe, just maybe: ary[counter++] = atof(strtok(rawdata, ","));

Upvotes: 0

David Morris
David Morris

Reputation: 136

Your call to fscanf is guaranteed to fail, as you have not provided an output argument. It should look like:

fscanf(inFilePtr, "%s", rawdata);

Your calls to strtok are also invalid. To continue tokenising the same string, the first argument of strtok should be NULL; strtok expects the second argument to still be a valid string.

Each of these issues would cause a segfault on their own. To ease your debugging in future, I would suggest either using a debugger and setting a breakpoint after the statement you are debugging, or commenting out other lines which you might expect to segfault (which typically includes anything that does anything with strings, if your code is in a fragile state.

Also, as a matter of style,

*(ary + counter)

Is normally written

ary[counter]

Upvotes: 2

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