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文件或目录的存取权限 快速理解Linux文件的权限，查看 Permissions, important and tricky! Unix permissions concern who can read a file or directory, write to it, and execute it. Permissions are granted or withheld with a magic 3-digit number. The three digits correspond to the owner (you); the group (?); and the world (everyone else). Think of each digit as a sum: execute permission = 1 write permission = 2 write and execute (1+2) = 3 read permission = 4 read and execute (4+1) = 5 read and write (4+2) = 6 read, write and execute (4+2+1) = 7 Add the number value of the permissions you want to grant each group to make a three digit number, one digit each for the owner, the group, and the world. Here are some useful combinations. Try to figure them out! 修改方式1：以绝对方式改变权限 chmod 600 {filespec}You can read and write; the world cant. Good for files. chmod 700 {filespec}You can read, write, and execute; the world cant. Good for scripts. chmod 644 {filespec}You can read and write; the world can only read. Good for web pages. chmod 755 {filespec}You can read, write, and execute; the world can read and execute. Good for programs you want to share, and your public_html directory. Permissions, another way(修改方式2：以符号模式改变权限(在原来基础上增加添加定义的权限)) You can also change file permissions with letters: u = user (yourself) g = group a = everyone r = read w = write x = execute chmod u+rw {filespec}Give yourself read and write permission chmod u+x {filespec}Give yourself execute permission. chmod a+rw {filespec}Give read and write permission to everyone. 使用文件命令对文件进行操作的前提是拥有相应的权限。下面我们介绍如何控制这些权限。 (1)用户和权限 Linux为每个文件都分配了一个文件所有者，称为文件主，并赋予文件主惟一的注册名。对文件的控制取决于文件主或超级用户（root）。文件或目录的创建者对创建的文件或目录拥有特别使用权。 文件的所有关系是可以改变的，可以将文件或目录的所有权转让给其它用户，但只有文件主或root用户才有权改变文件的所有关系。文件的所有权的标志是用户ID(UID)。 利用chown 命令可以更改某个文件或目录的所有权。例如，超级用户把自己的一个文件myfile拷贝给用户xu。为了让用户xu能够存取这个文件，超级用户（root）应该把这个文件的属主设为xu，否则，用户xu无法存取这个