statx(2) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | CONFORMING TO | SEE ALSO | COLOPHON

STATX(2)                Linux Programmer's Manual               STATX(2)

NAME         top

       statx - get file status (extended)

SYNOPSIS         top

       #include <fcntl.h>           /* Definition of AT_* constants */
       #include <sys/stat.h>

       int statx(int dirfd, const char *restrict pathname, int flags,
                 unsigned int mask, struct statx *restrict statxbuf);

DESCRIPTION         top

       This function returns information about a file, storing it in the
       buffer pointed to by statxbuf.  The returned buffer is a
       structure of the following type:

           struct statx {
               __u32 stx_mask;        /* Mask of bits indicating
                                         filled fields */
               __u32 stx_blksize;     /* Block size for filesystem I/O */
               __u64 stx_attributes;  /* Extra file attribute indicators */
               __u32 stx_nlink;       /* Number of hard links */
               __u32 stx_uid;         /* User ID of owner */
               __u32 stx_gid;         /* Group ID of owner */
               __u16 stx_mode;        /* File type and mode */
               __u64 stx_ino;         /* Inode number */
               __u64 stx_size;        /* Total size in bytes */
               __u64 stx_blocks;      /* Number of 512B blocks allocated */
               __u64 stx_attributes_mask;
                                      /* Mask to show what's supported
                                         in stx_attributes */

               /* The following fields are file timestamps */
               struct statx_timestamp stx_atime;  /* Last access */
               struct statx_timestamp stx_btime;  /* Creation */
               struct statx_timestamp stx_ctime;  /* Last status change */
               struct statx_timestamp stx_mtime;  /* Last modification */

               /* If this file represents a device, then the next two
                  fields contain the ID of the device */
               __u32 stx_rdev_major;  /* Major ID */
               __u32 stx_rdev_minor;  /* Minor ID */

               /* The next two fields contain the ID of the device
                  containing the filesystem where the file resides */
               __u32 stx_dev_major;   /* Major ID */
               __u32 stx_dev_minor;   /* Minor ID */
           };

       The file timestamps are structures of the following type:

           struct statx_timestamp {
               __s64 tv_sec;    /* Seconds since the Epoch (UNIX time) */
               __u32 tv_nsec;   /* Nanoseconds since tv_sec */
           };

       (Note that reserved space and padding is omitted.)

   Invoking statx():
       To access a file's status, no permissions are required on the
       file itself, but in the case of statx() with a pathname, execute
       (search) permission is required on all of the directories in
       pathname that lead to the file.

       statx() uses pathname, dirfd, and flags to identify the target
       file in one of the following ways:

       An absolute pathname
              If pathname begins with a slash, then it is an absolute
              pathname that identifies the target file.  In this case,
              dirfd is ignored.

       A relative pathname
              If pathname is a string that begins with a character other
              than a slash and dirfd is AT_FDCWD, then pathname is a
              relative pathname that is interpreted relative to the
              process's current working directory.

       A directory-relative pathname
              If pathname is a string that begins with a character other
              than a slash and dirfd is a file descriptor that refers to
              a directory, then pathname is a relative pathname that is
              interpreted relative to the directory referred to by
              dirfd.

       By file descriptor
              If pathname is an empty string and the AT_EMPTY_PATH flag
              is specified in flags (see below), then the target file is
              the one referred to by the file descriptor dirfd.

       flags can be used to influence a pathname-based lookup.  A value
       for flags is constructed by ORing together zero or more of the
       following constants:

       AT_EMPTY_PATH
              If pathname is an empty string, operate on the file
              referred to by dirfd (which may have been obtained using
              the open(2) O_PATH flag).  In this case, dirfd can refer
              to any type of file, not just a directory.

              If dirfd is AT_FDCWD, the call operates on the current
              working directory.

              This flag is Linux-specific; define _GNU_SOURCE to obtain
              its definition.

       AT_NO_AUTOMOUNT
              Don't automount the terminal ("basename") component of
              pathname if it is a directory that is an automount point.
              This allows the caller to gather attributes of an
              automount point (rather than the location it would mount).
              This flag can be used in tools that scan directories to
              prevent mass-automounting of a directory of automount
              points.  The AT_NO_AUTOMOUNT flag has no effect if the
              mount point has already been mounted over.  This flag is
              Linux-specific; define _GNU_SOURCE to obtain its
              definition.

       AT_SYMLINK_NOFOLLOW
              If pathname is a symbolic link, do not dereference it:
              instead return information about the link itself, like
              lstat(2).

       flags can also be used to control what sort of synchronization
       the kernel will do when querying a file on a remote filesystem.
       This is done by ORing in one of the following values:

       AT_STATX_SYNC_AS_STAT
              Do whatever stat(2) does.  This is the default and is very
              much filesystem-specific.

       AT_STATX_FORCE_SYNC
              Force the attributes to be synchronized with the server.
              This may require that a network filesystem perform a data
              writeback to get the timestamps correct.

       AT_STATX_DONT_SYNC
              Don't synchronize anything, but rather just take whatever
              the system has cached if possible.  This may mean that the
              information returned is approximate, but, on a network
              filesystem, it may not involve a round trip to the server
              - even if no lease is held.

       The mask argument to statx() is used to tell the kernel which
       fields the caller is interested in.  mask is an ORed combination
       of the following constants:

           STATX_TYPE          Want stx_mode & S_IFMT
           STATX_MODE          Want stx_mode & ~S_IFMT
           STATX_NLINK         Want stx_nlink
           STATX_UID           Want stx_uid
           STATX_GID           Want stx_gid
           STATX_ATIME         Want stx_atime
           STATX_MTIME         Want stx_mtime
           STATX_CTIME         Want stx_ctime
           STATX_INO           Want stx_ino
           STATX_SIZE          Want stx_size
           STATX_BLOCKS        Want stx_blocks
           STATX_BASIC_STATS   [All of the above]
           STATX_BTIME         Want stx_btime
           STATX_ALL           [All currently available fields]

       Note that, in general, the kernel does not reject values in mask
       other than the above.  (For an exception, see EINVAL in errors.)
       Instead, it simply informs the caller which values are supported
       by this kernel and filesystem via the statx.stx_mask field.
       Therefore, do not simply set mask to UINT_MAX (all bits set), as
       one or more bits may, in the future, be used to specify an
       extension to the buffer.

   The returned information
       The status information for the target file is returned in the
       statx structure pointed to by statxbuf.  Included in this is
       stx_mask which indicates what other information has been
       returned.  stx_mask has the same format as the mask argument and
       bits are set in it to indicate which fields have been filled in.

       It should be noted that the kernel may return fields that weren't
       requested and may fail to return fields that were requested,
       depending on what the backing filesystem supports.  (Fields that
       are given values despite being unrequested can just be ignored.)
       In either case, stx_mask will not be equal mask.

       If a filesystem does not support a field or if it has an
       unrepresentable value (for instance, a file with an exotic type),
       then the mask bit corresponding to that field will be cleared in
       stx_mask even if the user asked for it and a dummy value will be
       filled in for compatibility purposes if one is available (e.g., a
       dummy UID and GID may be specified to mount under some
       circumstances).

       A filesystem may also fill in fields that the caller didn't ask
       for if it has values for them available and the information is
       available at no extra cost.  If this happens, the corresponding
       bits will be set in stx_mask.

       Note: for performance and simplicity reasons, different fields in
       the statx structure may contain state information from different
       moments during the execution of the system call.  For example, if
       stx_mode or stx_uid is changed by another process by calling
       chmod(2) or chown(2), stat() might return the old stx_mode
       together with the new stx_uid, or the old stx_uid together with
       the new stx_mode.

       Apart from stx_mask (which is described above), the fields in the
       statx structure are:

       stx_blksize
              The "preferred" block size for efficient filesystem I/O.
              (Writing to a file in smaller chunks may cause an
              inefficient read-modify-rewrite.)

       stx_attributes
              Further status information about the file (see below for
              more information).

       stx_nlink
              The number of hard links on a file.

       stx_uid
              This field contains the user ID of the owner of the file.

       stx_gid
              This field contains the ID of the group owner of the file.

       stx_mode
              The file type and mode.  See inode(7) for details.

       stx_ino
              The inode number of the file.

       stx_size
              The size of the file (if it is a regular file or a
              symbolic link) in bytes.  The size of a symbolic link is
              the length of the pathname it contains, without a
              terminating null byte.

       stx_blocks
              The number of blocks allocated to the file on the medium,
              in 512-byte units.  (This may be smaller than stx_size/512
              when the file has holes.)

       stx_attributes_mask
              A mask indicating which bits in stx_attributes are
              supported by the VFS and the filesystem.

       stx_atime
              The file's last access timestamp.

       stx_btime
              The file's creation timestamp.

       stx_ctime
              The file's last status change timestamp.

       stx_mtime
              The file's last modification timestamp.

       stx_dev_major and stx_dev_minor
              The device on which this file (inode) resides.

       stx_rdev_major and stx_rdev_minor
              The device that this file (inode) represents if the file
              is of block or character device type.

       For further information on the above fields, see inode(7).

   File attributes
       The stx_attributes field contains a set of ORed flags that
       indicate additional attributes of the file.  Note that any
       attribute that is not indicated as supported by
       stx_attributes_mask has no usable value here.  The bits in
       stx_attributes_mask correspond bit-by-bit to stx_attributes.

       The flags are as follows:

       STATX_ATTR_COMPRESSED
              The file is compressed by the filesystem and may take
              extra resources to access.

       STATX_ATTR_IMMUTABLE
              The file cannot be modified: it cannot be deleted or
              renamed, no hard links can be created to this file and no
              data can be written to it.  See chattr(1).

       STATX_ATTR_APPEND
              The file can only be opened in append mode for writing.
              Random access writing is not permitted.  See chattr(1).

       STATX_ATTR_NODUMP
              File is not a candidate for backup when a backup program
              such as dump(8) is run.  See chattr(1).

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

       STATX_ATTR_VERITY (since Linux 5.5)
              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 (e.g., via
              a Merkle tree).

       STATX_ATTR_DAX (since Linux 5.8)
              The file is in the DAX (cpu direct access) state.  DAX
              state attempts to minimize software cache effects for both
              I/O and memory mappings of this file.  It requires a file
              system which has been configured to support DAX.

              DAX generally assumes all accesses are via CPU load /
              store instructions which can minimize overhead for small
              accesses, but may adversely affect CPU utilization for
              large transfers.

              File I/O is done directly to/from user-space buffers and
              memory mapped I/O may be performed with direct memory
              mappings that bypass the kernel page cache.

              While the DAX property tends to result in data being
              transferred synchronously, it does not give the same
              guarantees as the O_SYNC flag (see open(2)), where data
              and the necessary metadata are transferred together.

              A DAX file may support being mapped with the MAP_SYNC
              flag, which enables a program to use CPU cache flush
              instructions to persist CPU store operations without an
              explicit fsync(2).  See mmap(2) for more information.

RETURN VALUE         top

       On success, zero is returned.  On error, -1 is returned, and
       errno is set to indicate the error.

ERRORS         top

       EACCES Search permission is denied for one of the directories in
              the path prefix of pathname.  (See also
              path_resolution(7).)

       EBADF  dirfd is not a valid open file descriptor.

       EFAULT pathname or statxbuf is NULL or points to a location
              outside the process's accessible address space.

       EINVAL Invalid flag specified in flags.

       EINVAL Reserved flag specified in mask.  (Currently, there is one
              such flag, designated by the constant STATX__RESERVED,
              with the value 0x80000000U.)

       ELOOP  Too many symbolic links encountered while traversing the
              pathname.

       ENAMETOOLONG
              pathname is too long.

       ENOENT A component of pathname does not exist, or pathname is an
              empty string and AT_EMPTY_PATH was not specified in flags.

       ENOMEM Out of memory (i.e., kernel memory).

       ENOTDIR
              A component of the path prefix of pathname is not a
              directory or pathname is relative and dirfd is a file
              descriptor referring to a file other than a directory.

VERSIONS         top

       statx() was added to Linux in kernel 4.11; library support was
       added in glibc 2.28.

CONFORMING TO         top

       statx() is Linux-specific.

SEE ALSO         top

       ls(1), stat(1), access(2), chmod(2), chown(2), readlink(2),
       stat(2), utime(2), capabilities(7), inode(7), symlink(7)

COLOPHON         top

       This page is part of release 5.12 of the Linux man-pages project.
       A description of the project, information about reporting bugs,
       and the latest version of this page, can be found at
       https://www.kernel.org/doc/man-pages/.

Linux                          2021-03-22                       STATX(2)

Pages that refer to this page: stat(1)open(2)stat(2)syscalls(2)tmpfiles.d(5)inode(7)