sed: sed command a expects followed by text

在mac osx lion中sed来进行文件内容的替换操作，使用命令为：

sed -i 's/oldstring/newstring/g' full-path-file

执行后提示出错，错误信息为：“sed: 1: command a expects \ followed by text”，但是相同的命令拿到centos下确能执行成功。 使用man查看命令的参数详细说明，两个系统下对参数“i”的要求不一样。
mac osx中为：

-i extension
  Edit files in-place, saving backups with the specified extension.  If a zero-length extension is given, no backup will be saved.
  It is not recommended to give a zero-length extension when in-place editing files, as you risk corruption or partial content in situations where disk space is exhausted, etc.

centos中为：

-i[SUFFIX], --in-place[=SUFFIX]
  edit files in