====== Replace a string in a file with nant ======

File content:
<file cpp version.cpp>
  #include "stdio.h"
  #define VERSION "x.x.x.x"
  void main() {
  }
</file>

Create replace.build file to replace version with $BuildNumber:
 <file xml replace.build>
<version="1.0" encoding="utf-8" ?>
<project name="replace.line" default="replace">
  <target name="replace" descripton="replaces a line">
    
<loadfile file="${version.file}" property="version.file.content" />
  <regex
      input="${version.file.content}"
      pattern="(?'BEFORE'[\w\s\W]*)#define\sVERSION\s*&quot;[x][\.][x][\.][x][\.][x]&quot;(?'AFTER'[\w\s\W]*)" />
   <echo
      file="${version.file}"
      message="${BEFORE}#define VERSION &quot;${BuildNumber}&quot;${AFTER}"
      append="false" />

</target>

</project>
 </file>


Run it with: 
  nant -buildfile:replace.build -D:version.file=version.cpp -D:BuildNumber=9.1.0.1