class TracePoint

Returns a new TracePoint object, not enabled by default.

Next, in order to activate the trace, you must use TracePoint#enable

trace = TracePoint.new(:call) do |tp|
    p [tp.lineno, tp.defined_class, tp.method_id, tp.event]
end
#=> #<TracePoint:disabled>

trace.enable
#=> false

puts "Hello, TracePoint!"
# ...
# [48, IRB::Notifier::AbstractNotifier, :printf, :call]
# ...

When you want to deactivate the trace, you must use TracePoint#disable

trace.disable

See Events at TracePoint for possible events and more information.

A block must be given, otherwise an ArgumentError is raised.

If the trace method isn’t included in the given events filter, a RuntimeError is raised.

TracePoint.trace(:line) do |tp|
    p tp.raised_exception
end
#=> RuntimeError: 'raised_exception' not supported by this event

If the trace method is called outside block, a RuntimeError is raised.

TracePoint.trace(:line) do |tp|
  $tp = tp
end
$tp.lineno #=> access from outside (RuntimeError)

Access from other threads is also forbidden.

# File ruby_2_7_6/trace_point.rb, line 95
def self.new(*events)
  __builtin_tracepoint_new_s(events)
end

Returns internal information of TracePoint.

The contents of the returned value are implementation specific. It may be changed in future.

This method is only for debugging TracePoint itself.

# File ruby_2_7_6/trace_point.rb, line 117
def self.stat
  __builtin_tracepoint_stat_s
end

Document-method: trace

A convenience method for TracePoint.new, that activates the trace
automatically.

       trace = TracePoint.trace(:call) { |tp| [tp.lineno, tp.event] }
       #=> #<TracePoint:enabled>

       trace.enabled? #=> true

# File ruby_2_7_6/trace_point.rb, line 134
def self.trace(*events)
  __builtin_tracepoint_trace_s(events)
end

Return the generated binding object from event

# File ruby_2_7_6/trace_point.rb, line 313
def binding
  __builtin_tracepoint_attr_binding
end

Return the called name of the method being called

# File ruby_2_7_6/trace_point.rb, line 272
def callee_id
  __builtin_tracepoint_attr_callee_id
end

Return class or module of the method being called.

class C; def foo; end; end
trace = TracePoint.new(:call) do |tp|
  p tp.defined_class #=> C
end.enable do
  C.new.foo
end

If method is defined by a module, then that module is returned.

module M; def foo; end; end
class C; include M; end;
trace = TracePoint.new(:call) do |tp|
  p tp.defined_class #=> M
end.enable do
  C.new.foo
end

Note: defined_class returns singleton class.

6th block parameter of Kernel#set_trace_func passes original class of attached by singleton class.

This is a difference between Kernel#set_trace_func and TracePoint.

class C; def self.foo; end; end
trace = TracePoint.new(:call) do |tp|
  p tp.defined_class #=> #<Class:C>
end.enable do
  C.foo
end

# File ruby_2_7_6/trace_point.rb, line 308
def defined_class
  __builtin_tracepoint_attr_defined_class
end

Deactivates the trace

Return true if trace was enabled. Return false if trace was disabled.

trace.enabled?      #=> true
trace.disable       #=> true (previous status)
trace.enabled?      #=> false
trace.disable       #=> false

If a block is given, the trace will only be disable within the scope of the block.

trace.enabled?
#=> true

trace.disable do
    trace.enabled?
    # only disabled for this block
end

trace.enabled?
#=> true

Note: You cannot access event hooks within the block.

trace.disable { p tp.lineno }
#=> RuntimeError: access from outside

# File ruby_2_7_6/trace_point.rb, line 231
def disable
  __builtin_tracepoint_disable_m
end

Activates the trace.

Returns true if trace was enabled. Returns false if trace was disabled.

trace.enabled?  #=> false
trace.enable    #=> false (previous state)
                #   trace is enabled
trace.enabled?  #=> true
trace.enable    #=> true (previous state)
                #   trace is still enabled

If a block is given, the trace will only be enabled within the scope of the block.

trace.enabled?
#=> false

trace.enable do
  trace.enabled?
  # only enabled for this block
end

trace.enabled?
#=> false

target, target_line and target_thread parameters are used to limit tracing only to specified code objects. target should be a code object for which RubyVM::InstructionSequence.of will return an instruction sequence.

t = TracePoint.new(:line) { |tp| p tp }

def m1
  p 1
end

def m2
  p 2
end

t.enable(target: method(:m1))

m1
# prints #<TracePoint:line@test.rb:5 in `m1'>
m2
# prints nothing

Note: You cannot access event hooks within the enable block.

trace.enable { p tp.lineno }
#=> RuntimeError: access from outside

# File ruby_2_7_6/trace_point.rb, line 195
def enable(target: nil, target_line: nil, target_thread: nil)
  __builtin_tracepoint_enable_m(target, target_line, target_thread)
end

The current status of the trace

# File ruby_2_7_6/trace_point.rb, line 239
def enabled?
  __builtin_tracepoint_enabled_p
end

Compiled source code (String) on *eval methods on the :script_compiled event. If loaded from a file, it will return nil.

# File ruby_2_7_6/trace_point.rb, line 337
def eval_script
  __builtin_tracepoint_attr_eval_script
end

Type of event

See Events at TracePoint for more information.

# File ruby_2_7_6/trace_point.rb, line 246
def event
  __builtin_tracepoint_attr_event
end

Return a string containing a human-readable TracePoint status.

# File ruby_2_7_6/trace_point.rb, line 104
def inspect
  __builtin_tracepoint_inspect
end

Compiled instruction sequence represented by a RubyVM::InstructionSequence instance on the :script_compiled event.

Note that this method is MRI specific.

# File ruby_2_7_6/trace_point.rb, line 345
def instruction_sequence
  __builtin_tracepoint_attr_instruction_sequence
end

Line number of the event

# File ruby_2_7_6/trace_point.rb, line 251
def lineno
  __builtin_tracepoint_attr_lineno
end

Return the name at the definition of the method being called

# File ruby_2_7_6/trace_point.rb, line 267
def method_id
  __builtin_tracepoint_attr_method_id
end

Return the parameters definition of the method or block that the current hook belongs to. Format is the same as for Method#parameters

# File ruby_2_7_6/trace_point.rb, line 262
def parameters
  __builtin_tracepoint_attr_parameters
end

Path of the file being run

# File ruby_2_7_6/trace_point.rb, line 256
def path
  __builtin_tracepoint_attr_path
end

Value from exception raised on the :raise event

# File ruby_2_7_6/trace_point.rb, line 331
def raised_exception
  __builtin_tracepoint_attr_raised_exception
end

Return value from :return, c_return, and b_return event

# File ruby_2_7_6/trace_point.rb, line 326
def return_value
  __builtin_tracepoint_attr_return_value
end

Return the trace object during event

Same as TracePoint#binding:

trace.binding.eval('self')

# File ruby_2_7_6/trace_point.rb, line 321
def self
  __builtin_tracepoint_attr_self
end