error while trying to tokenizing a string and insert each part in an array

Question

while (fgets(buff, sizeof (char*)*100, file)) {
    if (line == 0) {
        fgets(buff, sizeof (char*)*100, file);
        line++;
    }

    int i = 0;
    char *p = strtok(buff, ",");
    char *array[10];

    while (p != NULL) {
        array[i++] = p;
        p = strtok(NULL, ",");
    }
    if (!strcmp(array[1], "03/04/2020")) {
        *inf += atof(array[i - 2]);
        *dead += atof(array[i - 1]);
        *rec += atof(array[i]);
    }

}

I'm trying to split the line which has the following format:

3245,03/04/2020,Jiangxi,Mainland China,2020-03-04T01:33:07,935.0,1.0,884.0

i tried using strtok with "," delimiter but I kept getting this `

RUN FAILED (exit value -1,073,741,819, total time: 1s

If my code is not clear PLEASE DO NOT HESITATE TO ASK ME ABOUT IT

Post a minimal reproducible example. As is, others can not successfully compile the posted code. — chux
– chux, Commented Mar 15, 2020 at 21:33
-1,073,741,819 is what you get when you print the DWORD 3,221,225,477 as a signed integer. 3,221,225,477 aka 0xC0000005 is what Windows uses to signal a Protection Fault ("SIGSEGV" in unix parlance). It means you are dereferencing a pointer variable that contains NULL or some other bad value. — ikegami
– ikegami, Commented Mar 15, 2020 at 21:41
Make sure i >= 2 after the loop, otherwise array[i-2] will access outside the array. — Barmar
– Barmar, Commented Mar 15, 2020 at 21:45
Errors will happen if there's a blank line in the file, since there won't be any tokens. — Barmar
– Barmar, Commented Mar 15, 2020 at 21:47
Instead of if (line == 0) test every time through the loop, skip the heading line by calling fgets() once before the loop. — Barmar
– Barmar, Commented Mar 15, 2020 at 21:48

Barmar · Accepted Answer · 2020-03-15 21:52:21Z

1

There's probably a blank line in the file. It won't have any tokens, so i will be 0 after the loop. array[i] will be uninitialized, and array[i-1] and array[i-2] will be outside the array, so accessing them causes undefined behavior.

Check that you've gotten enough tokens, and skip the line otherwise.

Also, since you increment i after assigning the token, array[i] is after the elements that you assigned. You should be using i-3, i-2, and i-1 to get the last 3 tokens.

// skip header line
fgets(buff, sizeof (char*)*100, file);

while (fgets(buff, sizeof (char*)*100, file)) {
    int i = 0;
    char *p = strtok(buff, ",");
    char *array[10];

    while (p != NULL) {
        array[i++] = p;
        p = strtok(NULL, ",");
    }
    if (i <= 3) { // skip lines that don't have enough tokens
        continue;
    }
    if (!strcmp(array[1], "03/04/2020")) {
        *inf += atof(array[i - 3]);
        *dead += atof(array[i - 2]);
        *rec += atof(array[i-1]);
    }
}

answered Mar 15, 2020 at 21:52

Barmar

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8 Comments

omar Over a year ago

the problem is i cannot skip any line because i need to extract the last three numbers from each line. Also, im sure that the file does not contain blank lines :(

Barmar Over a year ago

There may be a blank line at the end.

omar Over a year ago

and by the way, some lines may miss some elements such as : 3245,03/04/2020,,Mainland China,2020-03-04T01:33:07,935.0,1.0,884.0

omar Over a year ago

true, i just checked and found that theres a blank line at the end. what would you suggest doing to fix this ?

Barmar Over a year ago

That shouldn't be a problem since you don't use the empty fields. strtok() will store those as empty tokens.

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