title: exec ant replace a value in a .m file
body: <p>how to write an exec task in ant to replace two values in .m file.
  Because I want to replace the version number in iphone app, including my build number which i build using hudson, i remotely access the macos and get the app to be copied on to my windows
  system, so i generated the build using ant exec tasks, but now i want to replace my build number into the concern file before compiling,
  so how can i use exec task to replace certain values in a file.
  I know propertyfile task which replaces the value in a property file, but it doesn't work for
  this.</p>