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

NAME

     statx - get file status (extended)

SYNOPSIS

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

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

     Note: There is no glibc wrapper for statx(); see NOTES.

DESCRIPTION

     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 path-
            name that is interpreted relative to the process's current work-
            ing 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 direc-
            tory, 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 defini-
            tion.

     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 ker-
     nel 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 informa-
            tion 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 fol-
     lowing 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 the kernel does not reject values  in  mask  other  than  the
     above.   Instead,  it  simply  informs the caller which values are sup-
     ported 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 unrepre-
     sentable 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  com-
     patibility  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.  (Writ-
            ing 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  writ-
            ten 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 filesys-
            tem.

RETURN VALUE

     On success, zero is returned.  On error, -1 is returned, and  errno  is
     set appropriately.

ERRORS

     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.

     ELOOP  Too  many  symbolic links encountered while traversing the path-
            name.

     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

     statx() was added to Linux in kernel 4.11.

CONFORMING TO

     statx() is Linux-specific.

NOTES

     Glibc  does  not  (yet)  provide a wrapper for the statx() system call;
     call it using syscall(2).