原来cp 还有个--backup选项啊 真好

[lovelotus]

这个选项应该是check了timestamp吧，如果没有更新就不会copy了。很贴心啊

[eexpress]

--backup[=CONTROL]
make a backup of each existing destination file
-u, --update
copy only when the SOURCE file is newer than the destination
file or when the destination file is missing

仔细看。