statx

Statx is a Linux system call introduced with the 4.11 kernel to fetch file status information and metadata. It is designed to augment and, where appropriate, replace the older stat family (stat, lstat, fstatat) by offering more flexible querying, finer control over returned data, and nanosecond-level timestamps. The interface allows callers to request only the metadata they need, reducing overhead in some scenarios.

The statx API takes a directory file descriptor, a pathname, a set of flags, a mask indicating which fields to return, and a pointer to a struct statx that will be filled. A pathname can be resolved relative to the directory descriptor, and the AT_EMPTY_PATH flag enables querying the file associated with the directory file descriptor itself. Flags such as AT_SYMLINK_NOFOLLOW can be used to control linkage behavior. The mask selects which fields are to be populated, enabling efficient queries of only the relevant metadata.

The statx structure provides extended information beyond what stat offers. Returned fields can include file size, block count, block size, inode, device identifiers, ownership (UID, GID), mode bits, and timestamps for access, modification, and change, all with nanosecond resolution where supported. In addition, a set of capability and attribute flags can be reported, and a mask field indicates which fields were actually filled. This design supports more precise and potentially faster metadata retrieval, particularly on modern filesystems or network-backed storage.

Statx requires kernel support and compatible C library interfaces. It is widely supported in current distributions, but older software may rely on the traditional stat family. Use of statx can improve accuracy and efficiency in file system tooling, monitoring, and backup utilities.

See also: stat, lstat, fstatat, fstat.