psanford

#!/bin/bash
#
# usdt - trace user statically defined tracepoints. User-level dynamic tracing.
#        Written using Linux ftrace. Experimental.
#
# WARNING: This is a proof of concept for USDT tracing from Linux ftrace, and
# is not safe to use in production environments. In particular, the -i option
# sets memory semaphores by piping the output of printf through dd and then
# to process memory via /proc/PID/mem. Yes, this program pipes the output of
# the shell directly over top of live process memory. If you don't understand

psanford

# Here's the script I'll use to demonstrate - it just loops forever:

$ cat test.rb 
#!/usr/bin/env ruby

loop do
  sleep 1
end

# Now, I'll start the script in the background, and redirect stdout and stderr