balancedFile.c

int paren = 0, brace = 0, brack = 0;
for (int ch = fgetc(fp); ch != EOF; ch = fgetc(fp)) {
  if (ch == '(') paren++; if (ch == ')') paren--;
  if (ch == '{') brace++; if (ch == '}') brace--;
  if (ch == '[') brack++; if (ch == ']') brack--;
}
if (paren != 0 || brace != 0 || brack != 0) {
    fprintf(stderr, "unbalanced: %d %d %d\n", paren, brace, brack);
}