Apart from post-processing the strace output, there isn’t anything available to ignore failed system calls in strace. It wouldn’t be too hard to add, look at the syscall_exiting_trace function in syscall.c.
If you’d rather pursue the post-processing angle, Ole Tange has already taken care of that for you in a more comprehensive way than you’re likely to get here: the tracefile tool will run strace and filter out the information you’re after in a nicely readable fashion. See List the files accessed by a program for details. Another answer to that question lists other possible approaches, including LoggedFS which I find very useful.
Another option is to use SystemTap; for example
#!/usr/bin/env stapglobal stored_filename, stored_pathprobe syscall.open { stored_filename = filename}probe syscall.open.return { if (execname() == "cat"&& $return >= 0) { printf("opened %s\n", stored_filename) }}probe syscall.openat { stored_filename = filename stored_path = dfd_str}probe syscall.openat.return { if (execname() == "cat"&& $return >= 0) { printf("opened %s in %s\n", stored_filename, stored_path) }}will show the name of any file successfully opened by any cat process.