Ant OS specific value

<condition property="os.dep.value" value="value for MacOSX">
  <os family="mac" />
</condition>

<condition property="os.dep.value" value="value for Windows">
  <os family="windows" />
</condition>

<condition property="os.dep.value" value="value for Unix" >
  <os family="unix" />
</condition>

Use as "${os.dep.value}"

Creadit: Can I make the Ant copy task OS-specific? - Stack Overflow, How to make a conditional decision in an Ant build script based on operating system | java ant | devdaily.com