Debugging and Dumping the state of a running Ruby process using GDB.

Ruby GDB tricks

# Connect to ruby process
gdb `which ruby` <pid>

# Run GC
p rb_eval_string("GC.start")

# Count each Object class
p rb_eval_string("$gdb_objs = Hash.new 0")
p rb_eval_string("ObjectSpace.each_object {|o| $gdb_objs[o.class] += 1}")
p rb_eval_string("$stderr.puts($gdb_objs.inspect)")

# Show ObjectSpace.count_objects
p rb_eval_string("$stderr.puts(ObjectSpace.count_objects)")

# Print portion of every String - good if you need to find excessive duplication
p rb_eval_string("ObjectSpace.each_object {|v| $stderr.puts(v[0,132]) if v.is_a?(String)}")