Bash's ulimit currently does not support RLIMIT_RTTIME present in the Linux
kernel. If you think such support could be added, please consider using my
patch (in the attachment).
I had some trouble coming up with a string that shows up when invoking
ulimit -a. In the patch, it's "real-time cpu time" which is misleading,
since it suggests that this option is analogous to -t, (cpu time), which it
isn't. There's also a question which letter should be used to denote this