The file is compressed by the filesystem.

The file cannot be modified, as defined by chattr(1).

The file can only be opened in append mode for writing. See chattr(1).

The file is not a candidate for backup when a backup program scans the filesystem.

A key is required for the file to be encrypted by the filesystem.

The file has fs-verity enabled. It cannot be written to, and all reads from it will be verified against a cryptographic hash that covers the entire file.

The file is in the DAX (cpu direct access) state, which minimises page-cache effects for both I/O and memory mappings of this file.

• see https://www.kernel.org/doc/Documentation/filesystems/dax.txt

  Direct Access for Files

• since Linux 5.8

check ?mask attr t will check if t is set in attr.

If mask is not None then it will first check the mask to see if the file attribute is supported and if not raise Invalid_argument.