Since your file is line oriented, I would go with a safer solition just in case a line contains wonkiness.
Code:
#define BUF_SIZE 255
char *pnt, buffer[BUF_SIZE + 1];
int got;
char cmd[11];
...
for (...) {
if (!fgets(buffer, BUF_SIZE, fh))
break;
if (!(pnt = strchr(buffer, '\n'))) {
printf("No end-of-line detected. Too long for buffer or file terminates prematurely.\n");
exit_slow();
}
*pnt = '\0';
got = sscanf(buffer, "%.10s %d %d %d", cmd, &num1, &num2, &num3);
...
}
I'd have to check whether %.10s is the correct way to limit the number of bytes saved into cmd... But you could do that.
Then you check if got has whatever number of parameters expected... num1, num2, num3 values may be invalid based on that.