Module: Strace

Defined in:
lib/strace.rb

Overview

Simple wrapper of strace(1) for targetted tracing.

Constant Summary collapse

VERSION =

The version of strace_me you’re using

'1.0'

Class Method Summary collapse

Class Method Details

.me ⇒ Object

Runs strace(1) during the code in the block and returns an IO containing the strace output and the exception raised by the block (if any).

Simple example (it doesn’t matter if you have a /COPYRIGHT):

trace, err = Strace.me do
  open '/COPYRIGHT' do |io|
    io.read 1024
  end
end

puts "error: #{err.message} (#{err.class})\n\n" if err
puts "trace:\n\n#{trace.read}"

Tracing an existing library call:

alias old_connect connect

def connect host, user, password
  connection = nil

  trace, err = Strace.me do
    connection = old_connect host, user, password
  end

  $stderr.puts "connect trace:\n\n#{trace.read}"

  raise err if err
  connection
end



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# File 'lib/strace.rb', line 45

def self.me
  pid, i, o, e = Open4.open4 'strace', '-p', $$.to_s

  i.close
  e.gets # consumes "attached" message, but we know strace is ready

  begin
    yield
  ensure
    Process.kill 'INT', pid
    Process.waitpid pid

    return [e, $!]
  end
end