'\" t .\" Copyright (c) 2017 David Howells .\" .\" Derived from the stat.2 manual page: .\" Copyright (c) 1992 Drew Eckhardt (drew@cs.colorado.edu), March 28, 1992 .\" Parts Copyright (c) 1995 Nicolai Langfeldt (janl@ifi.uio.no), 1/1/95 .\" and Copyright (c) 2006, 2007, 2014 Michael Kerrisk .\" .\" %%%LICENSE_START(VERBATIM) .\" Permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" Permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" Since the Linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. The author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. The author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" Formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%LICENSE_END .\" .TH STATX 2 2017-03-07 "Linux" "Linux Programmer's Manual" .SH NAME statx \- Get file status (extended) .SH SYNOPSIS .nf .B #include .br .B #include .br .B #include .br .BR "#include " "/* Definition of AT_* constants */" .sp .BI "int statx(int " dirfd ", const char *" pathname ", int " flags "," .BI " unsigned int " mask ", struct statx *" buf ); .fi .sp .in -4n Feature Test Macro Requirements for glibc (see .BR feature_test_macros (7)): .in .ad l .PD 0 .sp .RS 4 .RE .PD .ad .SH DESCRIPTION .PP This function returns information about a file, storing it in the buffer pointed to by .IR buf . The buffer is filled in according to the following type: .PP .in +4n .nf 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 */ /* 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 device, then the next two feilds 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 contain the filesystem where the file resides */ __u32 stx_dev_major; /* Major ID */ __u32 stx_dev_minor; /* Minor ID */ }; .fi .in .PP The file timestamps are structures of the following type: .PP .in +4n .nf struct statx_timestamp { __s64 tv_sec; /* Seconds since the Epoch (UNIX time) */ __s32 tv_nsec; /* Nanoseconds before or since tv_sec */ }; .fi .in .PP (Note that reserved space and padding is omitted) .SS Invoking \fBstatx\fR(): .PP To access a file's status, no permissions are required on the file itself, but in the case of .BR statx () with a path, execute (search) permission is required on all of the directories in .I pathname that lead to the file. .PP .BR statx () uses .IR pathname , .IR dirfd , and .IR flags to locate the target file in one of a variety of ways: .TP [*] By absolute path. .I pathname points to an absolute path and .I dirfd is ignored. The file is looked up by name, starting from the root of the filesystem as seen by the calling process. .TP [*] By cwd-relative path. .I pathname points to a relative path and .IR dirfd is .BR AT_FDCWD . The file is looked up by name, starting from the current working directory. .TP [*] By dir-relative path. .I pathname points to relative path and .I dirfd indicates a file descriptor pointing to a directory. The file is looked up by name, starting from the directory specified by .IR dirfd . .TP [*] By file descriptor. .IR pathname " is " NULL " and " dirfd indicates a file descriptor. The file attached to the file descriptor is queried directly. The file descriptor may point to any type of file, not just a directory. .PP .I flags can be used to influence a path-based lookup. A value for .I flags is constructed by OR'ing together zero or more of the following constants: .TP .BR AT_EMPTY_PATH .\" commit 65cfc6722361570bfe255698d9cd4dccaf47570d If .I pathname is an empty string, operate on the file referred to by .IR dirfd (which may have been obtained using the .BR open (2) .B O_PATH flag). If .I dirfd is .BR AT_FDCWD , the call operates on the current working directory. In this case, .I dirfd can refer to any type of file, not just a directory. This flag is Linux-specific; define .B _GNU_SOURCE .\" Before glibc 2.16, defining _ATFILE_SOURCE sufficed to obtain its definition. .TP .BR AT_NO_AUTOMOUNT Don't automount the terminal ("basename") component of .I 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 .B AT_NO_AUTOMOUNT flag has no effect if the mount point has already been mounted over. This flag is Linux-specific; define .B _GNU_SOURCE .\" Before glibc 2.16, defining _ATFILE_SOURCE sufficed to obtain its definition. .TP .B AT_SYMLINK_NOFOLLOW If .I pathname is a symbolic link, do not dereference it: instead return information about the link itself, like .BR lstat (2). .PP .I 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 OR'ing in one of the following values: .TP .B AT_STATX_SYNC_AS_STAT Do whatever .BR stat (2) does. This is the default and is very much filesystem specific. .TP .B AT_STATX_FORCE_SYNC Force the attributes to be synchronised with the server. This may require that a network filesystem perform a data writeback to get the timestamps correct. .TP .B AT_STATX_DONT_SYNC Don't synchronise 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. .PP The .I mask argument to .BR statx () is used to tell the kernel which fields the caller is interested in. .I mask is an OR'ed combination of the following constants: .PP .in +4n .TS lB l. 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{,_ns} STATX_MTIME Want stx_mtime{,_ns} STATX_CTIME Want stx_ctime{,_ns} 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{,_ns} STATX_ALL [All currently available fields] .TE .in .PP .B "Do not" simply set .I mask to .B UINT_MAX as one or more bits may, in the future, be used to specify an extension to the buffer. .SS The returned information .PP The status information for the target file is returned in the .I statx structure pointed to by .IR buf . Included in this is .I stx_mask which indicates what other information has been returned. .I stx_mask has the same format as the mask argument and bits are set in it to indicate which fields have been filled in. .PP 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. In either case, .I stx_mask will not be equal .IR mask . .PP 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 .I 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). .PP A filesystem may also fill in fields that the caller didn't ask for if it has values for them available at no extra cost. If this happens, the corresponding bits will be set in .IR stx_mask . .PP .\" Background: inode attributes are modified with i_mutex held, but .\" read by stat() without taking the mutex. .I Note: For performance and simplicity reasons, different fields in the .I statx structure may contain state information from different moments during the execution of the system call. For example, if .IR stx_mode or .IR stx_uid is changed by another process by calling .BR chmod (2) or .BR chown (2), .BR stat () might return the old .I stx_mode together with the new .IR stx_uid , or the old .I stx_uid together with the new .IR stx_mode . .PP Apart from stx_mask (which is described above), the fields in the .I statx structure are: .TP .I stx_mode The file type and mode. This is described in more detail below. .TP .I 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. .TP .I stx_blocks The number of blocks allocated to the file on the medium, in 512-byte units. (This may be smaller than .IR stx_size /512 when the file has holes.) .TP .I stx_blksize The "preferred" blocksize for efficient filesystem I/O. (Writing to a file in smaller chunks may cause an inefficient read-modify-rewrite.) .TP .I stx_nlink The number of hard links on a file. .TP .I stx_uid The user ID of the file's owner. .TP .I stx_gid The ID of the group that may access the file. .TP .IR stx_dev_major " and " stx_dev_minor The device on which this file (inode) resides. .TP .IR stx_rdev_major " and " stx_rdev_minor The device that this file (inode) represents if the file is of block or character device type. .TP .I stx_attributes Further status information about the file (see below for more information). .TP .I stx_atime The file's last access timestamp. This field is changed by file accesses, for example, by .BR execve (2), .BR mknod (2), .BR pipe (2), .BR utime (2), and .BR read (2) (of more than zero bytes). Other routines, such as .BR mmap (2), may or may not update it. .TP .I stx_btime The file's creation timestamp. This is set on file creation and not changed subsequently. .TP .I stx_ctime The file's last status change timestamp. This field is changed by writing or by setting inode information (i.e., owner, group, link count, mode, etc.). .TP .I stx_mtime The file's last modification timestamp. This is changed by file modifications, for example, by .BR mknod (2), .BR truncate (2), .BR utime (2), and .BR write (2) (of more than zero bytes). Moreover, the modification time of a directory is changed by the creation or deletion of files in that directory. This field is .I not changed for changes in owner, group, hard link count, or mode. .PP Not all of the Linux filesystems implement all of the timestamp fields. Some filesystems allow mounting in such a way that file and/or directory accesses do not cause an update of the .I stx_atime field. (See .IR noatime , .IR nodiratime , and .I relatime in .BR mount (8), and related information in .BR mount (2).) In addition, .I stx_atime is not updated if a file is opened with the .BR O_NOATIME ; see .BR open (2). .\" .SS File attributes .PP The .I stx_attributes field contains a set of OR'ed flags that indicate additional attributes of the file: .TP STATX_ATTR_COMPRESSED The file is compressed by the fs and may take extra resources to access. .TP 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 .BR chattr (1). .TP STATX_ATTR_APPEND The file can only be opened in append mode for writing. Random access writing is not permitted. See .BR chattr (1). .TP STATX_ATTR_NODUMP File is not a candidate for backup when a backup program such as .BR dump (8) is run. See .BR chattr (1). .TP STATX_ATTR_ENCRYPTED A key is required for the file to be encrypted by the filesystem. .SS File type and mode .PP The .I stx_mode field contains the combined file type and mode. POSIX refers to the bits in this field corresponding to the mask .B S_IFMT (see below) as the .IR "file type" , the 12 bits corresponding to the mask 07777 as the .IR "file mode bits" and the least significant 9 bits (0777) as the .IR "file permission bits" . .IP The following mask values are defined for the file type of the .I stx_mode field: .in +4n .TS lB l l. S_IFMT 0170000 bit mask for the file type bit field S_IFSOCK 0140000 socket S_IFLNK 0120000 symbolic link S_IFREG 0100000 regular file S_IFBLK 0060000 block device S_IFDIR 0040000 directory S_IFCHR 0020000 character device S_IFIFO 0010000 FIFO .TE .in .IP Note that .I stx_mode has two mask flags covering it: one for the type and one for the mode bits. .PP To test for a regular file (for example), one could write: .nf .in +4n statx(AT_FDCWD, pathname, 0, STATX_TYPE, &sb); if ((sb.stx_mask & STATX_TYPE) && (sb.stx_mode & S_IFMT) == S_IFREG) { /* Handle regular file */ } .in .fi .PP Because tests of the above form are common, additional macros are defined by POSIX to allow the test of the file type in .I stx_mode to be written more concisely: .RS 4 .TS lB l. \fBS_ISREG\fR(m) Is it a regular file? \fBS_ISDIR\fR(m) Is it a directory? \fBS_ISCHR\fR(m) Is it a character device? \fBS_ISBLK\fR(m) Is it a block device? \fBS_ISFIFO\fR(m) Is it a FIFO (named pipe)? \fBS_ISLNK\fR(m) Is it a symbolic link? (Not in POSIX.1-1996.) \fBS_ISSOCK\fR(m) Is it a socket? (Not in POSIX.1-1996.) .TE .RE .PP The preceding code snippet could thus be rewritten as: .nf .in +4n statx(AT_FDCWD, pathname, 0, STATX_TYPE, &sb); if ((sb.stx_mask & STATX_TYPE) && S_ISREG(sb.stx_mode)) { /* Handle regular file */ } .in .fi .PP The definitions of most of the above file type test macros are provided if any of the following feature test macros is defined: .BR _BSD_SOURCE (in glibc 2.19 and earlier), .BR _SVID_SOURCE (in glibc 2.19 and earlier), or .BR _DEFAULT_SOURCE (in glibc 2.20 and later). In addition, definitions of all of the above macros except .BR S_IFSOCK and .BR S_ISSOCK () are provided if .BR _XOPEN_SOURCE is defined. The definition of .BR S_IFSOCK can also be exposed by defining .BR _XOPEN_SOURCE with a value of 500 or greater. The definition of .BR S_ISSOCK () is exposed if any of the following feature test macros is defined: .BR _BSD_SOURCE (in glibc 2.19 and earlier), .BR _DEFAULT_SOURCE (in glibc 2.20 and later), .BR _XOPEN_SOURCE with a value of 500 or greater, or .BR _POSIX_C_SOURCE with a value of 200112L or greater. .PP The following mask values are defined for the file mode component of the .I stx_mode field: .in +4n .TS lB l l. S_ISUID 04000 set-user-ID bit S_ISGID 02000 set-group-ID bit (see below) S_ISVTX 01000 sticky bit (see below) S_IRWXU 00700 owner has read, write, and execute permission S_IRUSR 00400 owner has read permission S_IWUSR 00200 owner has write permission S_IXUSR 00100 owner has execute permission S_IRWXG 00070 group has read, write, and execute permission S_IRGRP 00040 group has read permission S_IWGRP 00020 group has write permission S_IXGRP 00010 group has execute permission S_IRWXO 00007 T{ others (not in group) have read, write, and execute permission T} S_IROTH 00004 others have read permission S_IWOTH 00002 others have write permission S_IXOTH 00001 others have execute permission .TE .in .P The set-group-ID bit .RB ( S_ISGID ) has several special uses. For a directory, it indicates that BSD semantics is to be used for that directory: files created there inherit their group ID from the directory, not from the effective group ID of the creating process, and directories created there will also get the .B S_ISGID bit set. For a file that does not have the group execution bit .RB ( S_IXGRP ) set, the set-group-ID bit indicates mandatory file/record locking. .P The sticky bit .RB ( S_ISVTX ) on a directory means that a file in that directory can be renamed or deleted only by the owner of the file, by the owner of the directory, and by a privileged process. .SH RETURN VALUE On success, zero is returned. On error, \-1 is returned, and .I errno is set appropriately. .SH ERRORS .TP .B EINVAL Invalid flag specified in .IR flags . .TP .B EACCES Search permission is denied for one of the directories in the path prefix of .IR pathname . (See also .BR path_resolution (7).) .TP .B EBADF .I dirfd is not a valid open file descriptor. .TP .B EFAULT Bad address. .TP .B ELOOP Too many symbolic links encountered while traversing the path. .TP .B ENAMETOOLONG .I pathname is too long. .TP .B ENOENT A component of .I pathname does not exist, or .I pathname is an empty string and AT_EMPTY_PATH was not specified. .TP .B ENOMEM Out of memory (i.e., kernel memory). .TP .B ENOTDIR A component of the path prefix of .I pathname is not a directory or .I pathname is relative and .I dirfd is a file descriptor referring to a file other than a directory. .SH VERSIONS .BR statx () was added to Linux in kernel 4.11; library support is not yet added to glibc. .SH SEE ALSO .BR ls (1), .BR stat (1), .BR access (2), .BR chmod (2), .BR chown (2), .BR stat (2), .BR readlink (2), .BR utime (2), .BR capabilities (7), .BR symlink (7)