rt allow to run programs in real time under Linux

Download it with: wget -O rt.c http://dwnl.nisu.org/dwnl/rt.c/dwnl

Compile it doing: gcc -s -o /usr/local/sbin/rt rt.c

Usage /usr/local/sbin/rt [ -m msg ][ -s seconds ][ -p pid ][ -q pid ][ -n ][-x program [args] --- ]
 -s causes background and continues after a while
 -p sets RT to pid (pid=0 is last pid)
 -q removes RT to pid
 -x run in RT program with args
 -m set the next message, can contain %d, use -m '' to avoid default messages.
Arguments are processed sequentially and can be repeated, except -n that causes program to exit
rt will only wait for first -x program

Examples:
  /usr/local/sbin/rt -m $'Sleep %d seconds\n' -s 4 -m $'Removing RT to %d\n' -q 333 \
     -m $'Sleep %d more seconds\n' -s 5 -m $'You arent yet in RT\n' -q $$

  /usr/local/sbin/rt -m $'Runing sleep 100\n' -x sleep 100 --- \
     -s 10 -m $'sleep not yet in RT\n' -q 0

  /usr/local/sbin/rt -m '' -s 5 -m $'Setting caller proces %d in RT\n' -p 0

  # sleep 60 in RT during 5 secons, do no wait for sleep 100
  /usr/local/sbin/rt -x sleep 60 --- -s 5 -q 0 -x sleep 100 --- -s 5 -q 0
  # to see better the effect, run:
  /usr/local/sbin/rt -x bash -c 'sleep 60; echo a' --- -s 5 -q 0 -x bash -c 'sleep 100; echo b' --- -s 5 -q 0

  # after 10 seconds 'runload' will not be in RT, BUT 'bash' will be, if you have only a processor your system will crash.
  /usr/local/sbin/rt -x runload -t 1 bash -c 'while true; do true; done' --- -s 10 -q 0

If not called by root, dont process any argument, simply removes RT of the caller process (bash, for example) and exit with status=2

Put your sshd in RT:

/etc/rc.local
/usr/local/sbin/rt -p $(</var/run/sshd.init.pid) # or /var/run/sshd.pid

/etc/profile
[ "$SSH_CLIENT" ] && 
  /usr/local/sbin/rt -m $'\n\n\nDo not start any daemon in the next 30 seconds\n\n\n\n' \
                     -s 30 -m $'\a' -q $$
/etc/bash.bashrc
[ "$SSH_CLIENT" ] &&
  /usr/local/sbin/rt -m '' -s 30 -m '' -q $$

To see who is in RT:
top -n 1 -b | grep RT