man2/statx.2

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   2 .\" Copyright (c) 2017 David Howells <dhowells@redhat.com>
   3 .\"
   4 .\" Derived from the stat.2 manual page:
   5 .\"   Copyright (c) 1992 Drew Eckhardt (drew@cs.colorado.edu), March 28, 1992
   6 .\"   Parts Copyright (c) 1995 Nicolai Langfeldt (janl@ifi.uio.no), 1/1/95
   7 .\"   and Copyright (c) 2006, 2007, 2014 Michael Kerrisk <mtk.manpages@gmail.com>
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  31 .TH STATX 2 2019-03-06 "Linux" "Linux Programmer's Manual"
  32 .SH NAME
  33 statx \- get file status (extended)
  34 .SH SYNOPSIS
  35 .nf
  36 .B #include <sys/types.h>
  37 .B #include <sys/stat.h>
  38 .B #include <unistd.h>
  39 .BR "#include <fcntl.h>           " "/* Definition of AT_* constants */"
  40 .PP
  41 .BI "int statx(int " dirfd ", const char *" pathname ", int " flags ","
  42 .BI "          unsigned int " mask ", struct statx *" statxbuf );
  43 .fi
  44 .PP
  45 .SH DESCRIPTION
  46 .PP
  47 This function returns information about a file, storing it in the buffer
  48 pointed to by
  49 .IR statxbuf .
  50 The returned buffer is a structure of the following type:
  51 .PP
  52 .in +4n
  53 .EX
  54 struct statx {
  55     __u32 stx_mask;        /* Mask of bits indicating
  56                               filled fields */
  57     __u32 stx_blksize;     /* Block size for filesystem I/O */
  58     __u64 stx_attributes;  /* Extra file attribute indicators */
  59     __u32 stx_nlink;       /* Number of hard links */
  60     __u32 stx_uid;         /* User ID of owner */
  61     __u32 stx_gid;         /* Group ID of owner */
  62     __u16 stx_mode;        /* File type and mode */
  63     __u64 stx_ino;         /* Inode number */
  64     __u64 stx_size;        /* Total size in bytes */
  65     __u64 stx_blocks;      /* Number of 512B blocks allocated */
  66     __u64 stx_attributes_mask;
  67                            /* Mask to show what's supported
  68                               in stx_attributes */
  69
  70     /* The following fields are file timestamps */
  71     struct statx_timestamp stx_atime;  /* Last access */
  72     struct statx_timestamp stx_btime;  /* Creation */
  73     struct statx_timestamp stx_ctime;  /* Last status change */
  74     struct statx_timestamp stx_mtime;  /* Last modification */
  75
  76     /* If this file represents a device, then the next two
  77        fields contain the ID of the device */
  78     __u32 stx_rdev_major;  /* Major ID */
  79     __u32 stx_rdev_minor;  /* Minor ID */
  80
  81     /* The next two fields contain the ID of the device
  82        containing the filesystem where the file resides */
  83     __u32 stx_dev_major;   /* Major ID */
  84     __u32 stx_dev_minor;   /* Minor ID */
  85 };
  86 .EE
  87 .in
  88 .PP
  89 The file timestamps are structures of the following type:
  90 .PP
  91 .in +4n
  92 .EX
  93 struct statx_timestamp {
  94     __s64 tv_sec;    /* Seconds since the Epoch (UNIX time) */
  95     __u32 tv_nsec;   /* Nanoseconds since tv_sec */
  96 };
  97 .EE
  98 .in
  99 .PP
 100 (Note that reserved space and padding is omitted.)
 101 .SS
 102 Invoking \fBstatx\fR():
 103 .PP
 104 To access a file's status, no permissions are required on the file itself,
 105 but in the case of
 106 .BR statx ()
 107 with a pathname,
 108 execute (search) permission is required on all of the directories in
 109 .I pathname
 110 that lead to the file.
 111 .PP
 112 .BR statx ()
 113 uses
 114 .IR pathname ,
 115 .IR dirfd ,
 116 and
 117 .IR flags
 118 to identify the target file in one of the following ways:
 119 .TP
 120 An absolute pathname
 121 If
 122 .I pathname
 123 begins with a slash,
 124 then it is an absolute pathname that identifies the target file.
 125 In this case,
 126 .I dirfd
 127 is ignored.
 128 .TP
 129 A relative pathname
 130 If
 131 .I pathname
 132 is a string that begins with a character other than a slash and
 133 .IR dirfd
 134 is
 135 .BR AT_FDCWD ,
 136 then
 137 .I pathname
 138 is a relative pathname that is interpreted relative to the process's
 139 current working directory.
 140 .TP
 141 A directory-relative pathname
 142 If
 143 .I pathname
 144 is a string that begins with a character other than a slash and
 145 .I dirfd
 146 is a file descriptor that refers to a directory, then
 147 .I pathname
 148 is a relative pathname that is interpreted relative to the directory
 149 referred to by
 150 .IR dirfd .
 151 .TP
 152 By file descriptor
 153 If
 154 .IR pathname
 155 is an empty string and the
 156 .B AT_EMPTY_PATH
 157 flag is specified in
 158 .IR flags
 159 (see below),
 160 then the target file is the one referred to by the file descriptor
 161 .IR dirfd .
 162 .PP
 163 .I flags
 164 can be used to influence a pathname-based lookup.
 165 A value for
 166 .I flags
 167 is constructed by ORing together zero or more of the following constants:
 168 .TP
 169 .BR AT_EMPTY_PATH
 170 .\" commit 65cfc6722361570bfe255698d9cd4dccaf47570d
 171 If
 172 .I pathname
 173 is an empty string, operate on the file referred to by
 174 .IR dirfd
 175 (which may have been obtained using the
 176 .BR open (2)
 177 .B O_PATH
 178 flag).
 179 In this case,
 180 .I dirfd
 181 can refer to any type of file, not just a directory.
 182 .IP
 183 If
 184 .I dirfd
 185 is
 186 .BR AT_FDCWD ,
 187 the call operates on the current working directory.
 188 .IP
 189 This flag is Linux-specific; define
 190 .B _GNU_SOURCE
 191 .\" Before glibc 2.16, defining _ATFILE_SOURCE sufficed
 192 to obtain its definition.
 193 .TP
 194 .BR AT_NO_AUTOMOUNT
 195 Don't automount the terminal ("basename") component of
 196 .I pathname
 197 if it is a directory that is an automount point.
 198 This allows the caller to gather attributes of an automount point
 199 (rather than the location it would mount).
 200 This flag can be used in tools that scan directories
 201 to prevent mass-automounting of a directory of automount points.
 202 The
 203 .B AT_NO_AUTOMOUNT
 204 flag has no effect if the mount point has already been mounted over.
 205 This flag is Linux-specific; define
 206 .B _GNU_SOURCE
 207 .\" Before glibc 2.16, defining _ATFILE_SOURCE sufficed
 208 to obtain its definition.
 209 .TP
 210 .B AT_SYMLINK_NOFOLLOW
 211 If
 212 .I pathname
 213 is a symbolic link, do not dereference it:
 214 instead return information about the link itself, like
 215 .BR lstat (2).
 216 .PP
 217 .I flags
 218 can also be used to control what sort of synchronization the kernel will do
 219 when querying a file on a remote filesystem.
 220 This is done by ORing in one of the following values:
 221 .TP
 222 .B AT_STATX_SYNC_AS_STAT
 223 Do whatever
 224 .BR stat (2)
 225 does.
 226 This is the default and is very much filesystem-specific.
 227 .TP
 228 .B AT_STATX_FORCE_SYNC
 229 Force the attributes to be synchronized with the server.
 230 This may require that
 231 a network filesystem perform a data writeback to get the timestamps correct.
 232 .TP
 233 .B AT_STATX_DONT_SYNC
 234 Don't synchronize anything, but rather just take whatever
 235 the system has cached if possible.
 236 This may mean that the information returned is approximate, but,
 237 on a network filesystem, it may not involve a round trip to the server - even
 238 if no lease is held.
 239 .PP
 240 The
 241 .I mask
 242 argument to
 243 .BR statx ()
 244 is used to tell the kernel which fields the caller is interested in.
 245 .I mask
 246 is an ORed combination of the following constants:
 247 .PP
 248 .in +4n
 249 .TS
 250 lB l.
 251 STATX_TYPE      Want stx_mode & S_IFMT
 252 STATX_MODE      Want stx_mode & ~S_IFMT
 253 STATX_NLINK     Want stx_nlink
 254 STATX_UID       Want stx_uid
 255 STATX_GID       Want stx_gid
 256 STATX_ATIME     Want stx_atime
 257 STATX_MTIME     Want stx_mtime
 258 STATX_CTIME     Want stx_ctime
 259 STATX_INO       Want stx_ino
 260 STATX_SIZE      Want stx_size
 261 STATX_BLOCKS    Want stx_blocks
 262 STATX_BASIC_STATS       [All of the above]
 263 STATX_BTIME     Want stx_btime
 264 STATX_ALL       [All currently available fields]
 265 .TE
 266 .in
 267 .PP
 268 Note that the kernel does
 269 .I not
 270 reject values in
 271 .I mask
 272 other than the above.
 273 Instead, it simply informs the caller which values are supported
 274 by this kernel and filesystem via the
 275 .I statx.stx_mask
 276 field.
 277 Therefore,
 278 .I "do not"
 279 simply set
 280 .I mask
 281 to
 282 .B UINT_MAX
 283 (all bits set),
 284 as one or more bits may, in the future, be used to specify an
 285 extension to the buffer.
 286 .SS
 287 The returned information
 288 .PP
 289 The status information for the target file is returned in the
 290 .I statx
 291 structure pointed to by
 292 .IR statxbuf .
 293 Included in this is
 294 .I stx_mask
 295 which indicates what other information has been returned.
 296 .I stx_mask
 297 has the same format as the
 298 .I mask
 299 argument and bits are set in it to indicate
 300 which fields have been filled in.
 301 .PP
 302 It should be noted that the kernel may return fields that weren't
 303 requested and may fail to return fields that were requested,
 304 depending on what the backing filesystem supports.
 305 (Fields that are given values despite being unrequested can just be ignored.)
 306 In either case,
 307 .I stx_mask
 308 will not be equal
 309 .IR mask .
 310 .PP
 311 If a filesystem does not support a field or if it has
 312 an unrepresentable value (for instance, a file with an exotic type),
 313 then the mask bit corresponding to that field will be cleared in
 314 .I stx_mask
 315 even if the user asked for it and a dummy value will be filled in for
 316 compatibility purposes if one is available (e.g., a dummy UID and GID may be
 317 specified to mount under some circumstances).
 318 .PP
 319 A filesystem may also fill in fields that the caller didn't ask for if it has
 320 values for them available and the information is available at no extra cost.
 321 If this happens, the corresponding bits will be set in
 322 .IR stx_mask .
 323 .PP
 324 .\" Background: inode attributes are modified with i_mutex held, but
 325 .\" read by stat() without taking the mutex.
 326 .IR Note :
 327 for performance and simplicity reasons, different fields in the
 328 .I statx
 329 structure may contain state information from different moments
 330 during the execution of the system call.
 331 For example, if
 332 .IR stx_mode
 333 or
 334 .IR stx_uid
 335 is changed by another process by calling
 336 .BR chmod (2)
 337 or
 338 .BR chown (2),
 339 .BR stat ()
 340 might return the old
 341 .I stx_mode
 342 together with the new
 343 .IR stx_uid ,
 344 or the old
 345 .I stx_uid
 346 together with the new
 347 .IR stx_mode .
 348 .PP
 349 Apart from
 350 .I stx_mask
 351 (which is described above), the fields in the
 352 .I statx
 353 structure are:
 354 .TP
 355 .I stx_blksize
 356 The "preferred" block size for efficient filesystem I/O.
 357 (Writing to a file in
 358 smaller chunks may cause an inefficient read-modify-rewrite.)
 359 .TP
 360 .I stx_attributes
 361 Further status information about the file (see below for more information).
 362 .TP
 363 .I stx_nlink
 364 The number of hard links on a file.
 365 .TP
 366 .I stx_uid
 367 This field contains the user ID of the owner of the file.
 368 .TP
 369 .I stx_gid
 370 This field contains the ID of the group owner of the file.
 371 .TP
 372 .I stx_mode
 373 The file type and mode.
 374 See
 375 .BR inode (7)
 376 for details.
 377 .TP
 378 .I stx_ino
 379 The inode number of the file.
 380 .TP
 381 .I stx_size
 382 The size of the file (if it is a regular file or a symbolic link) in bytes.
 383 The size of a symbolic link is the length of the pathname it contains,
 384 without a terminating null byte.
 385 .TP
 386 .I stx_blocks
 387 The number of blocks allocated to the file on the medium, in 512-byte units.
 388 (This may be smaller than
 389 .IR stx_size /512
 390 when the file has holes.)
 391 .TP
 392 .I stx_attributes_mask
 393 A mask indicating which bits in
 394 .IR stx_attributes
 395 are supported by the VFS and the filesystem.
 396 .TP
 397 .I stx_atime
 398 The file's last access timestamp.
 399 .TP
 400 .I stx_btime
 401 The file's creation timestamp.
 402 .TP
 403 .I stx_ctime
 404 The file's last status change timestamp.
 405 .TP
 406 .I stx_mtime
 407 The file's last modification timestamp.
 408 .TP
 409 .IR stx_dev_major " and "  stx_dev_minor
 410 The device on which this file (inode) resides.
 411 .TP
 412 .IR stx_rdev_major " and "  stx_rdev_minor
 413 The device that this file (inode) represents if the file is of block or
 414 character device type.
 415 .PP
 416 For further information on the above fields, see
 417 .BR inode (7).
 418 .\"
 419 .SS File attributes
 420 .PP
 421 The
 422 .I stx_attributes
 423 field contains a set of ORed flags that indicate additional attributes
 424 of the file.
 425 Note that any attribute that is not indicated as supported by
 426 .I stx_attributes_mask
 427 has no usable value here.
 428 The bits in
 429 .I stx_attributes_mask
 430 correspond bit-by-bit to
 431 .IR stx_attributes .
 432 .PP
 433 The flags are as follows:
 434 .TP
 435 .B STATX_ATTR_COMPRESSED
 436 The file is compressed by the filesystem and may take extra resources
 437 to access.
 438 .TP
 439 .B STATX_ATTR_IMMUTABLE
 440 The file cannot be modified: it cannot be deleted or renamed,
 441 no hard links can be created to this file and no data can be written to it.
 442 See
 443 .BR chattr (1).
 444 .TP
 445 .B STATX_ATTR_APPEND
 446 The file can only be opened in append mode for writing.
 447 Random access writing
 448 is not permitted.
 449 See
 450 .BR chattr (1).
 451 .TP
 452 .B STATX_ATTR_NODUMP
 453 File is not a candidate for backup when a backup program such as
 454 .BR dump (8)
 455 is run.
 456 See
 457 .BR chattr (1).
 458 .TP
 459 .B STATX_ATTR_ENCRYPTED
 460 A key is required for the file to be encrypted by the filesystem.
 461 .SH RETURN VALUE
 462 On success, zero is returned.
 463 On error, \-1 is returned, and
 464 .I errno
 465 is set appropriately.
 466 .SH ERRORS
 467 .TP
 468 .B EACCES
 469 Search permission is denied for one of the directories
 470 in the path prefix of
 471 .IR pathname .
 472 (See also
 473 .BR path_resolution (7).)
 474 .TP
 475 .B EBADF
 476 .I dirfd
 477 is not a valid open file descriptor.
 478 .TP
 479 .B EFAULT
 480 .I pathname
 481 or
 482 .I statxbuf
 483 is NULL or points to a location outside the process's
 484 accessible address space.
 485 .TP
 486 .B EINVAL
 487 Invalid flag specified in
 488 .IR flags .
 489 .TP
 490 .B EINVAL
 491 Reserved flag specified in
 492 .IR mask .
 493 .TP
 494 .B ELOOP
 495 Too many symbolic links encountered while traversing the pathname.
 496 .TP
 497 .B ENAMETOOLONG
 498 .I pathname
 499 is too long.
 500 .TP
 501 .B ENOENT
 502 A component of
 503 .I pathname
 504 does not exist, or
 505 .I pathname
 506 is an empty string and
 507 .B AT_EMPTY_PATH
 508 was not specified in
 509 .IR flags .
 510 .TP
 511 .B ENOMEM
 512 Out of memory (i.e., kernel memory).
 513 .TP
 514 .B ENOTDIR
 515 A component of the path prefix of
 516 .I pathname
 517 is not a directory or
 518 .I pathname
 519 is relative and
 520 .I dirfd
 521 is a file descriptor referring to a file other than a directory.
 522 .SH VERSIONS
 523 .BR statx ()
 524 was added to Linux in kernel 4.11; library support was added in glibc 2.28.
 525 .SH CONFORMING TO
 526 .BR statx ()
 527 is Linux-specific.
 528 .SH SEE ALSO
 529 .BR ls (1),
 530 .BR stat (1),
 531 .BR access (2),
 532 .BR chmod (2),
 533 .BR chown (2),
 534 .BR readlink (2),
 535 .BR stat (2),
 536 .BR utime (2),
 537 .BR capabilities (7),
 538 .BR inode (7),
 539 .BR symlink (7)