fscanf and dynamic array allocation

Question

I am trying to read something from a txt file using fscanf. I am only reading a word in each time. And I am counting how many words I've collected. So that I can create a dynamic array with the count of words. Each element of array will contain a word. But I don't know how. Here is my code

pFile = fopen(inFile, "r");
char *chr;
if(pFile != NULL) // Process if the file is not empty
{
    while(!feof(pFile))
    {
        chr = (char*)malloc(sizeof(char*));
        num++;
        fscanf(pFile, "%s", chr);
    }
    printf("%s",chr);

}

And my example of the txt file is like that: hello world

Please [do not cast](http://stackoverflow.com/q/605845/2173917) the return value of `malloc()`. — Sourav Ghosh, Dec 30 '14 at 10:20
also, usage instruction related to [`feof()`](http://stackoverflow.com/q/5431941/2173917) — Sourav Ghosh, Dec 30 '14 at 10:22
@SouravGhosh we really need a tag that automatically expands to "do not cast the result of malloc" with the suitable link :p — Quentin, Dec 30 '14 at 10:30

Yu Hao · Answer 1 · 2014-12-30T10:18:25.093

1

sizeof is a compile time operator (with the exception of variable length array). In particular, sizeof(char*) is the size of a pointer to char, which is normally 4 in 32-bit machines, or 8 in 64-bit machines. So the size is not as dynamic as you thought.

An alternative is to malloc a small array first, use fgets to get the line, if the size is too small (you can check if a \n is got), realloc to a bigger size. Use sscanf to get the data from the line.

Also, you never free the memory dynamically allocated, so there's memory leak.

edited Dec 30 '14 at 10:18

answered Dec 30 '14 at 10:12

Yu Hao

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Thank you I used free afterwards I know but im not about that one. I want to create an array withthe amount of read words.. – phoeNix Dec 30 '14 at 10:15

fscanf and dynamic array allocation

1 Answers1