ant使用exec执行shell

<target name="versioncode">
        <exec executable="sh" outputproperty="v_code">
            <arg value="-c" />
            <arg value="svnversion | sed -e 's/^[^:]*://;s/[A-Za-z]//'" />
        </exec>
        <echo>Revision (app): ${v_code}</echo>
        <replaceregexp file="AndroidManifest.xml" match='android:versionCode="0"' replace='android:versionCode="${v_code}"' />
    </target>