POSIX says that octal escapes have the format \ddd in the format string,

but \0ddd in a %b argument, with a length restriction of 3 octal digits
in either case. This seems silly, but it needs to be right so it's possible
to write an octal escape followed by an ordinary digit. Solaris printf(1)
and GNU printf(1) also behave this way.

Example: "printf '\0752'" now produces "=2" instead of garbage.

usr.bin/printf/printf.c

@@ -408,7 +408,8 @@ escape(char *fmt, int percent, size_t *len)
 					/* octal constant */
 		case '0': case '1': case '2': case '3':
 		case '4': case '5': case '6': case '7':
-			for (c = *fmt == '0' ? 4 : 3, value = 0;
+			c = (!percent && *fmt == '0') ? 4 : 3;
+			for (value = 0;
 			    c-- && *fmt >= '0' && *fmt <= '7'; ++fmt) {
 				value <<= 3;
 				value += *fmt - '0';