如下是UNIX系统中目录权限和文件权限的含义：

　　　　　　　　TABLE 1. UNIX DIRECTORY Permissions

WHO	WHAT THE PERMISSIONS ALLOW
USER	Read (r)	The account owner can list the files in the directory.
	Write (w)	The account owner can create or delete files in the directory.
	Execute (x)	access files in that directory by name (such as Web page files).
GROUP	Read (r)	Everyone in the designated group can list the files in the directory.
	Write (w)	Everyone in the group can create or delete files in the directory.
	Execute (x)	Everyone in the group can change (cd) into the directory and access files in that directory by name (such as Web page files).
OTHER	Read (r)	Anyone can list the files in the directory.
	Write (w)	Anyone can create or delete files in the directory.
	Execute (x)	Anyone can change (cd) into the directory and access files in that directory by name (such as Web page files).

　　　　　　　　TABLE 2. UNIX FILE Permissions

WHO	WHAT THE PERMISSIONS ALLOW
USER	Read (r)	The account owner can read the file.
	Write (w)	The account owner can modify or delete the file.
	Execute (x)	The account owner can run the file as a program.
GROUP	Read (r)	Everyone in the designated group can read the file.
	Write (w)	Everyone in the group can modify or delete the file.
	Execute (x)	Everyone in the group can can run the file as a program.
OTHER	Read (r)	Anyone can read the file.
	Write (w)	Anyone can modify or delete the file.
	Execute (x)	Anyone can run the file as a program.

对于文件的权限，实际上并不象表2中所示那样简单。因为考虑一个文件的权限时，还需要考虑文件所在的各级目录的权限问题(root用户除外)。

1. 用户对文件的读权限

　需要满足条件：

　(1) 对于文件本身，用户有读权限，即表2中所列的读(r)权限。

　(2) 对于文件所在的各级目录(从根目录一直到文件所在目录)，用户均需有执行(x)权限。

2. 用户对文件的删除权限

　文件本身的权限中并没有对“删除”权限的限制，实际上对文件的“删除”权限，是通过目录的写(w)权限来限制的。

需要满足条件：

　　　用户在文件所在各级目录上都有执行(x)权限，同时需要在文件所在目录(注意不是各级目录)具有写(w)权限。

3. 用户对文件的写权限 (与读权限类似)

　需要满足条件：

　(1) 对于文件本身，用户有写权限，即表2中所列的写(w)权限。

　(2) 对于文件所在的各级目录(从根目录一直到文件所在目录)，用户均需有执行(x)权限。

4. 用户对文件的创建权限 (与删除权限类似)

文件本身的权限中并没有对“创建”权限的限制，对文件的“创建”权限，是通过目录的写(w)权限来限制的。

　需要满足条件：

　　　用户在各级目录上都有执行(x)权限，同时需要在创建文件的目录上具有写(w)权限。

5. 列出目录中文件权限

需要满足条件：

用户在各级目录上都有执行(x)权限，同时需要在最后一级目录上具有读(r)权限。

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UNIX中文件权限与目录权限