How to make fscanf function skip a line?

How to make fscanf function skip a line?

I think you could:

void skip_nl(FILE *f) {
    char c[2];
    fscanf(f, "%1[\n]", c) == 1 || fscanf(f, "%*[^\n]%*1[\n]");
}

Note that scanning %*[^\n] will fail when there will be an empty line ("fail", as in scanf will stop scanning). So if there is an empty line, %*[^\n] will scan nothing and scanf will just return. So an empty line has to be handled specially, and fscanf return value is used to detect if the scan was succesfull or not. Note that %* discarded scanning does not increment scanf return value. So first scanf("%1[\n]" with a temporary unused buffer just "detects" (and discards) an empty line. If the line is not an empty line, then %*[^\n] scans and discards one or more non-newline characters and after that %*1[\n] discards a single newline character. If you are sure that the input will not be just a newline, then %*[^\n]%*1[\n] is fine. Tested on godbolt.

But really writing the following is really not that hard...:

for (int c; (c = getc(f)) != EOF && c != '\n'; ) {}