linux中umask系统变量

在linux中umask是一个系统变量，它的作用是：当文件被创建时，为文件的访问权限设定一个掩码。

执行umask命令可以修改这个变量的值。它是一个由3个八进制数字组成的值。每个数字都是八进制

值1、2、4的OR的结果。他们的具体含义如下表：

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数字                                                 取值                                                 含义                          

1                                                       0                                                      允许属主的任何权限

                                                         4                                                      禁止属主的读权限

                                                         2                                                      禁止属主的写权限

                                                         1                                                      禁止属主的执行权限

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2                                                       0                                                      允许组任何权限

                                                         4                                                      禁止组的读权限

                                                         2                                                      禁止组的写权限

                                                         1                                                      禁止组的执行权限

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3                                                       0                                                      允许其他人的任何权限

                                                         4                                                      禁止其他人的读权限

                                                         2                                                      禁止其他人的写权限

                                                         1                                                      禁止其他人的执行权限

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例如，如果要禁止组的写权限和执行权限，同时禁止其他用户的写权限，那么umask值应该如下表所示：

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数字                                                                                                 含义

1                                                                                                        0

2                                                                                                        2

                                                                                                          1

3                                                                                                        2

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每个数字的取值OR在一起，因此第2个数字的值是 2 | 1，结果为3。最终的umask值为032.