instance method

Kernel#set_trace_func

set_trace_func(proc) → proc

set_trace_func(nil) → nil

static VALUE
set_trace_func(VALUE obj, VALUE trace)
{
    rb_remove_event_hook(call_trace_func);

    if (NIL_P(trace)) {
        return Qnil;
    }

    if (!rb_obj_is_proc(trace)) {
        rb_raise(rb_eTypeError, "trace_func needs to be Proc");
    }

    rb_add_event_hook(call_trace_func, RUBY_EVENT_ALL, trace);
    return trace;
}

Establishes proc as the handler for tracing, or disables tracing if the parameter is nil.

Note: this method is obsolete, please use TracePoint instead.

proc takes up to six parameters:

an event name string
a filename string
a line number
a method name symbol, or nil
a binding, or nil
the class, module, or nil

proc is invoked whenever an event occurs.

Events are:

"c-call": call a C-language routine
"c-return": return from a C-language routine
"call": call a Ruby method
"class": start a class or module definition
"end": finish a class or module definition
"line": execute code on a new line
"raise": raise an exception
"return": return from a Ruby method

Tracing is disabled within the context of proc.

Example

class Test
  def test
    a = 1
    b = 2
  end
end

set_trace_func proc { |event, file, line, id, binding, class_or_module|
  printf "%8s %s:%-2d %16p %14p\n", event, file, line, id, class_or_module
}
t = Test.new
t.test

Produces:

c-return prog.rb:8   :set_trace_func         Kernel
    line prog.rb:11              nil            nil
  c-call prog.rb:11             :new          Class
  c-call prog.rb:11      :initialize    BasicObject
c-return prog.rb:11      :initialize    BasicObject
c-return prog.rb:11             :new          Class
    line prog.rb:12              nil            nil
    call prog.rb:2             :test           Test
    line prog.rb:3             :test           Test
    line prog.rb:4             :test           Test
  return prog.rb:5             :test           Test

See also #select #sleep #require_relative #spawn also in 4.1 · 3.4 · 3.3 · 3.2 · 3.1 · 3.0

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