class Tracer

Outputs a source level execution trace of a Ruby program.

It does this by registering an event handler with Kernel#set_trace_func for processing incoming events. It also provides methods for filtering unwanted trace output (see ::add_filter, ::on, and ::off).

Example ↑

Consider the following Ruby script

class A
  def square(a)
    return a*a
  end
end

a = A.new
a.square(5)

Running the above script using ruby -r tracer example.rb will output the following trace to STDOUT (Note you can also explicitly require 'tracer')

#0:<internal:lib/rubygems/custom_require>:38:Kernel:<: -
#0:example.rb:3::-: class A
#0:example.rb:3::C: class A
#0:example.rb:4::-:   def square(a)
#0:example.rb:7::E: end
#0:example.rb:9::-: a = A.new
#0:example.rb:10::-: a.square(5)
#0:example.rb:4:A:>:   def square(a)
#0:example.rb:5:A:-:     return a*a
#0:example.rb:6:A:<:   end
 |  |         | |  |
 |  |         | |   ---------------------+ event
 |  |         |  ------------------------+ class
 |  |          --------------------------+ line
 |   ------------------------------------+ filename
  ---------------------------------------+ thread

Symbol table used for displaying incoming events:

+}+

call a C-language routine

+{+

return from a C-language routine

+>+

call a Ruby method

C

start a class or module definition

E

finish a class or module definition

-

execute code on a new line

+^+

raise an exception

+<+

return from a Ruby method

by Keiju ISHITSUKA(keiju@ishitsuka.com)

Constants

EVENT_SYMBOL

Symbol table used for displaying trace information

Single

Reference to singleton instance of Tracer

display_c_call
display_process_id
display_thread_id
stdout
verbose

Attributes

display_c_call[RW]

display C-routine calls in trace output (defaults to false)

display_c_call?[RW]

display C-routine calls in trace output (defaults to false)

display_process_id[RW]

display process id in trace output (defaults to false)

display_process_id?[RW]

display process id in trace output (defaults to false)

display_thread_id[RW]

display thread id in trace output (defaults to true)

display_thread_id?[RW]

display thread id in trace output (defaults to true)

stdout[RW]

output stream used to output trace (defaults to STDOUT)

stdout_mutex[R]

mutex lock used by tracer for displaying trace output

verbose[RW]

display additional debug information (defaults to false)

verbose?[RW]

display additional debug information (defaults to false)

Public Class Methods

add_filter(p = proc) click to toggle source

Used to filter unwanted trace output

Example which only outputs lines of code executed within the Kernel class:

Tracer.add_filter do |event, file, line, id, binding, klass, *rest|
  "Kernel" == klass.to_s
end

# File lib/tracer.rb, line 263
def Tracer.add_filter(p = proc)
  Single.add_filter(p)
end
off() click to toggle source

Disable tracing

# File lib/tracer.rb, line 236
def Tracer.off
  Single.off
end
on() { || ... } click to toggle source

Start tracing

Example ↑

Tracer.on
# code to trace here
Tracer.off

You can also pass a block:

Tracer.on {
  # trace everything in this block
}

# File lib/tracer.rb, line 225
def Tracer.on
  if block_given?
    Single.on{yield}
  else
    Single.on
  end
end
set_get_line_procs(file_name, p = proc) click to toggle source

Register an event handler p which is called everytime a line in file_name is executed.

Example:

Tracer.set_get_line_procs("example.rb", lambda { |line|
  puts "line number executed is #{line}"
})

# File lib/tracer.rb, line 250
def Tracer.set_get_line_procs(file_name, p = proc)
  Single.set_get_line_procs(file_name, p)
end