文件的模式
fs.chmod() 和 fs.chmodSync() 方法中使用的 mode 参数是使用以下常量的逻辑或创建的数字位掩码：
The mode argument used in both the fs.chmod() and fs.chmodSync()
methods is a numeric bitmask created using a logical OR of the following
constants:
| Constant | Octal | Description |
|---|---|---|
fs.constants.S_IRUSR | 0o400 | read by owner |
fs.constants.S_IWUSR | 0o200 | write by owner |
fs.constants.S_IXUSR | 0o100 | execute/search by owner |
fs.constants.S_IRGRP | 0o40 | read by group |
fs.constants.S_IWGRP | 0o20 | write by group |
fs.constants.S_IXGRP | 0o10 | execute/search by group |
fs.constants.S_IROTH | 0o4 | read by others |
fs.constants.S_IWOTH | 0o2 | write by others |
fs.constants.S_IXOTH | 0o1 | execute/search by others |
An easier method of constructing the mode is to use a sequence of three
octal digits (e.g. 765). The left-most digit (7 in the example), specifies
the permissions for the file owner. The middle digit (6 in the example),
specifies permissions for the group. The right-most digit (5 in the example),
specifies the permissions for others.
| Number | Description |
|---|---|
7 | read, write, and execute |
6 | read and write |
5 | read and execute |
4 | read only |
3 | write and execute |
2 | write only |
1 | execute only |
0 | no permission |
For example, the octal value 0o765 means:
- The owner may read, write, and execute the file.
- The group may read and write the file.
- Others may read and execute the file.
When using raw numbers where file modes are expected, any value larger than
0o777 may result in platform-specific behaviors that are not supported to work
consistently. Therefore constants like S_ISVTX, S_ISGID, or S_ISUID are
not exposed in fs.constants.
Caveats: on Windows only the write permission can be changed, and the distinction among the permissions of group, owner, or others is not implemented.
