The co command's -l option locks the file so that you (and only you) can edit it.
co 命令的 -l 选项可以锁定该文件，以便您（并且只有您）可以对其进行编辑。
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Modify control: control the outgoing file is allowed to co - operate the file for the two edit. Unauthorized, the file can only be read can not be modified.