docs, src: updates usage text for utilities

src/dj.c

@@ -313,9 +313,9 @@ parse(char *s){
 static int
 usage(void){
 
-	fprintf(stderr, "Usage: %s (-AdfHqQ) (-a [byte]) (-c [count])\n"
-		"\t(-i [input file]) (-b [input block size]) (-s [input offset])\n"
-		"\t(-o [output file]) (-B [output block size]) (-S [output offset])\n",
+	fprintf(stderr, "Usage: %s [-AdfHqQ] [-a byte] [-c count]\n"
+		"\t[-i input_file] [-b input_block_size] [-s input_offset]\n"
+		"\t[-o output_file] [-B output_block_size] [-S output_offset]\n",
 		program_name);
 
 	return EX_USAGE;