bsd/man/man2/stat.2

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  34 .\"     @(#)stat.2      8.3 (Berkeley) 4/19/94
  35 .\"
  36 .Dd May 15, 2008
  37 .Dt STAT 2
  38 .Os BSD 4
  39 .Sh NAME
  40 .Nm fstat ,
  41 .Nm fstat64 ,
  42 .Nm lstat ,
  43 .Nm lstat64 ,
  44 .Nm stat ,
  45 .Nm stat64 ,
  46 .Nm fstatat
  47 .Nd get file status
  48 .Sh SYNOPSIS
  49 .Fd #include <sys/stat.h>
  50 .Ft int
  51 .Fo fstat
  52 .Fa "int fildes"
  53 .Fa "struct stat *buf"
  54 .Fc
  55 .Ft int
  56 .Fo lstat
  57 .Fa "const char *restrict path"
  58 .Fa "struct stat *restrict buf"
  59 .Fc
  60 .Ft int
  61 .Fo stat
  62 .Fa "const char *restrict path"
  63 .Fa "struct stat *restrict buf"
  64 .Fc
  65 .Ft int
  66 .Fn fstatat "int fd" "const char *path" "struct stat *buf" "int flag"
  67 .Sh TRANSITIIONAL SYNOPSIS (NOW DEPRECATED)
  68 .Ft int
  69 .br
  70 .Fo fstat64
  71 .Fa "int fildes"
  72 .Fa "struct stat64 *buf"
  73 .Fc ;
  74 .sp
  75 .Ft int
  76 .br
  77 .Fo lstat64
  78 .Fa "const char *restrict path"
  79 .Fa "struct stat64 *restrict buf"
  80 .Fc ;
  81 .sp
  82 .Ft int
  83 .br
  84 .Fo stat64
  85 .Fa "const char *restrict path"
  86 .Fa "struct stat64 *restrict buf"
  87 .Fc ;
  88 .Sh DESCRIPTION
  89 The
  90 .Fn stat
  91 function obtains information about the file pointed to by
  92 .Fa path .
  93 Read, write or execute
  94 permission of the named file is not required, but all directories
  95 listed in the path name leading to the file must be searchable.
  96 .Pp
  97 The
  98 .Fn lstat
  99 function
 100 is like
 101 .Fn stat
 102 except in the case where the named file is a symbolic link;
 103 .Fn lstat
 104 returns information about the link,
 105 while
 106 .Fn stat
 107 returns information about the file the link references.
 108 The attributes cannot be relied on in case of symbolic links.
 109 In this case, the only attributes returned from an
 110 .Fn lstat
 111 that refer to the symbolic link itself are the file type (S_IFLNK),
 112 size, blocks, and link count (always 1).
 113 .Pp
 114 The
 115 .Fn fstat
 116 obtains the same information about an open file
 117 known by the file descriptor
 118 .Fa fildes .
 119 .Pp
 120 The
 121 .Fn fstatat
 122 system call is equivalent to
 123 .Fn stat
 124 and
 125 .Fn lstat
 126 except in the case where the
 127 .Fa path
 128 specifies a relative path.
 129 In this case the status is retrieved from a file relative to
 130 the directory associated with the file descriptor
 131 .Fa fd
 132 instead of the current working directory.
 133 .Pp
 134 The values for the
 135 .Fa flag
 136 are constructed by a bitwise-inclusive OR of flags from the following list,
 137 defined in
 138 .In fcntl.h :
 139 .Bl -tag -width indent
 140 .It Dv AT_SYMLINK_NOFOLLOW
 141 If
 142 .Fa path
 143 names a symbolic link, the status of the symbolic link is returned.
 144 .El
 145 .Pp
 146 If
 147 .Fn fstatat
 148 is passed the special value
 149 .Dv AT_FDCWD
 150 in the
 151 .Fa fd
 152 parameter, the current working directory is used and the behavior is
 153 identical to a call to
 154 .Fn stat
 155 or
 156 .Fn lstat
 157 respectively, depending on whether or not the
 158 .Dv AT_SYMLINK_NOFOLLOW
 159 bit is set in
 160 .Fa flag .
 161 .Pp
 162 The
 163 .Fa buf
 164 argument is a pointer to a
 165 .Fa stat
 166 structure
 167 as defined by
 168 .Aq Pa sys/stat.h
 169 and into which information is placed concerning the file.
 170 When the macro
 171 .Dv _DARWIN_FEATURE_64_BIT_INODE
 172 is not defined (see below for more information about this macro), the
 173 .Fa stat
 174 structure is defined as:
 175 .Bd -literal
 176 struct stat { /* when _DARWIN_FEATURE_64_BIT_INODE is NOT defined */
 177     dev_t    st_dev;    /* device inode resides on */
 178     ino_t    st_ino;    /* inode's number */
 179     mode_t   st_mode;   /* inode protection mode */
 180     nlink_t  st_nlink;  /* number of hard links to the file */
 181     uid_t    st_uid;    /* user-id of owner */
 182     gid_t    st_gid;    /* group-id of owner */
 183     dev_t    st_rdev;   /* device type, for special file inode */
 184     struct timespec st_atimespec;  /* time of last access */
 185     struct timespec st_mtimespec;  /* time of last data modification */
 186     struct timespec st_ctimespec;  /* time of last file status change */
 187     off_t    st_size;   /* file size, in bytes */
 188     quad_t   st_blocks; /* blocks allocated for file */
 189     u_long   st_blksize;/* optimal file sys I/O ops blocksize */
 190     u_long   st_flags;  /* user defined flags for file */
 191     u_long   st_gen;    /* file generation number */
 192 };
 193 .Ed
 194 .Pp
 195 However, when the macro
 196 .Dv _DARWIN_FEATURE_64_BIT_INODE
 197 is defined, the
 198 .Fa stat
 199 structure will now be defined as:
 200 .Bd -literal
 201 struct stat { /* when _DARWIN_FEATURE_64_BIT_INODE is defined */
 202     dev_t           st_dev;           /* ID of device containing file */
 203     mode_t          st_mode;          /* Mode of file (see below) */
 204     nlink_t         st_nlink;         /* Number of hard links */
 205     ino_t           st_ino;           /* File serial number */
 206     uid_t           st_uid;           /* User ID of the file */
 207     gid_t           st_gid;           /* Group ID of the file */
 208     dev_t           st_rdev;          /* Device ID */
 209     struct timespec st_atimespec;     /* time of last access */
 210     struct timespec st_mtimespec;     /* time of last data modification */
 211     struct timespec st_ctimespec;     /* time of last status change */
 212     struct timespec st_birthtimespec; /* time of file creation(birth) */
 213     off_t           st_size;          /* file size, in bytes */
 214     blkcnt_t        st_blocks;        /* blocks allocated for file */
 215     blksize_t       st_blksize;       /* optimal blocksize for I/O */
 216     uint32_t        st_flags;         /* user defined flags for file */
 217     uint32_t        st_gen;           /* file generation number */
 218     int32_t         st_lspare;        /* RESERVED: DO NOT USE! */
 219     int64_t         st_qspare[2];     /* RESERVED: DO NOT USE! */
 220 };
 221 .Ed
 222 .Pp
 223 The time-related fields of
 224 .Fa struct stat
 225 are as follows:
 226 .Bl -tag -width XXXst_birthtime
 227 .It st_atime
 228 Time when file data last accessed.
 229 Changed by the
 230 .Xr mknod 2 ,
 231 .Xr utimes 2
 232 and
 233 .Xr read 2
 234 system calls.
 235 .It st_mtime
 236 Time when file data last modified.
 237 Changed by the
 238 .Xr mknod 2 ,
 239 .Xr utimes 2
 240 and
 241 .Xr write 2
 242 system calls.
 243 .It st_ctime
 244 Time when file status was last changed (inode data modification).
 245 Changed by the
 246 .Xr chmod 2 ,
 247 .Xr chown 2 ,
 248 .Xr link 2 ,
 249 .Xr mknod 2 ,
 250 .Xr rename 2 ,
 251 .Xr unlink 2 ,
 252 .Xr utimes 2
 253 and
 254 .Xr write 2
 255 system calls.
 256 .It st_birthtime
 257 Time of file creation. Only set once when the file is created. This field is
 258 only available in the 64 bit inode variants. On filesystems where birthtime is
 259 not available, this field is set to 0 (i.e. epoch).
 260 .El
 261 .Pp
 262 The size-related fields of the structures are as follows:
 263 .Bl -tag -width XXXst_blksize
 264 .It st_blksize
 265 The optimal I/O block size for the file.
 266 .It st_blocks
 267 The actual number of blocks allocated for the file in 512-byte units.
 268 As short symbolic links are stored in the inode, this number may
 269 be zero.
 270 .El
 271 .Pp
 272 The status information word
 273 .Fa st_mode
 274 has the following bits:
 275 .Bd -literal
 276 #define S_IFMT 0170000           /* type of file */
 277 #define        S_IFIFO  0010000  /* named pipe (fifo) */
 278 #define        S_IFCHR  0020000  /* character special */
 279 #define        S_IFDIR  0040000  /* directory */
 280 #define        S_IFBLK  0060000  /* block special */
 281 #define        S_IFREG  0100000  /* regular */
 282 #define        S_IFLNK  0120000  /* symbolic link */
 283 #define        S_IFSOCK 0140000  /* socket */
 284 #define        S_IFWHT  0160000  /* whiteout */
 285 #define S_ISUID 0004000  /* set user id on execution */
 286 #define S_ISGID 0002000  /* set group id on execution */
 287 #define S_ISVTX 0001000  /* save swapped text even after use */
 288 #define S_IRUSR 0000400  /* read permission, owner */
 289 #define S_IWUSR 0000200  /* write permission, owner */
 290 #define S_IXUSR 0000100  /* execute/search permission, owner */
 291 .Ed
 292 .Pp
 293 For a list of access modes, see
 294 .Aq Pa sys/stat.h ,
 295 .Xr access 2
 296 and
 297 .Xr chmod 2 .
 298 .Pp
 299 For a list of the file flags in the
 300 .Fa st_flags
 301 field, see
 302 .Aq Pa sys/stat.h
 303 and
 304 .Xr chflags 2 .
 305 .Sh _DARWIN_FEATURE_64_BIT_INODE
 306 In order to accommodate advanced capabilities of newer file systems, the
 307 .Fa struct stat ,
 308 .Fa struct statfs ,
 309 and
 310 .Fa struct dirent
 311 data structures were updated in Mac OSX 10.5.
 312 .Pp
 313 The most obvious change is the increased size of
 314 .Fa ino_t
 315 from 32 bits to 64 bits.  As a consequence, storing an ino_t in an int is
 316 no longer safe, and file formats storing ino_t as 32-bit values may need to
 317 be updated.  There are other changes as well, such as the widening of
 318 .Fa f_fstypename ,
 319 .Fa f_mntonname ,
 320 and
 321 .Fa f_mntfromname
 322 in
 323 .Fa struct statfs .
 324 Please refer to
 325 .Xr stat 2
 326 and
 327 .Xr dir 5
 328 for more detail on the specific changes to the other affected data structures.
 329 .Pp
 330 On platforms that existed before these updates were available, ABI
 331 compatibility is achieved by providing two implementations for related
 332 functions: one using the legacy data structures and one using the updated
 333 data structures.  Variants which make use of the newer structures have their
 334 symbols suffixed with $INODE64.  These $INODE64 suffixes are automatically
 335 appended by the compiler tool-chain and should not be used directly.
 336 .Pp
 337 Platforms that were released after these updates only have the newer variants
 338 available to them.  These platforms have the macro
 339 .Dv _DARWIN_FEATURE_ONLY_64_BIT_INODE
 340 defined.
 341 .Pp
 342 The
 343 .Dv _DARWIN_FEATURE_64_BIT_INODE
 344 macro should not be set directly.  Instead, developers should make use of the
 345 .Dv _DARWIN_NO_64_BIT_INODE
 346 or
 347 .Dv _DARWIN_USE_64_BIT_INODE
 348 macros when the default variant is not desired.  The following table details
 349 the effects of defining these macros for different deployment targets.
 350 .Pp
 351 .TS
 352 center;
 353 c s s s
 354 l | c s s
 355 c | c c c
 356 c | c c c
 357 l | c c c.
 358 T{
 359 .Dv _DARWIN_FEATURE_ONLY_64_BIT_INODE Sy not defined
 360 T}
 361 =
 362         Deployment Target
 363 user defines:   < 10.5  10.5    > 10.5
 364 _
 365 T{
 366 .Em (none)
 367 T}      32-bit  32-bit  64-bit
 368 T{
 369 .Dv _DARWIN_NO_64_BIT_INODE
 370 T}      32-bit  32-bit  32-bit
 371 T{
 372 .Dv _DARWIN_USE_64_BIT_INODE
 373 T}      32-bit  64-bit  64-bit
 374 _
 375 .T&
 376 c s s s
 377 c s s s
 378 c | l s s
 379 c | c c c
 380 l | c c c.
 381
 382 T{
 383 .Dv _DARWIN_FEATURE_ONLY_64_BIT_INODE Sy defined
 384 T}
 385 =
 386 user defines:   Any Deployment Target
 387 _
 388 T{
 389 .Em (none)
 390 T}      64-bit-only
 391 T{
 392 .Dv _DARWIN_NO_64_BIT_INODE
 393 T}      T{
 394 .Em (error)
 395 T}
 396 T{
 397 .Dv _DARWIN_USE_64_BIT_INODE
 398 T}      64-bit-only
 399 _
 400 .TE
 401 .Pp
 402 .Bl -tag -width 64-bit-only -offset indent
 403 .It 32-bit
 404 32-bit inode values are enabled, and the legacy structures involving the
 405 .Vt ino_t
 406 type are in use.
 407 The macro
 408 .Dv _DARWIN_FEATURE_64_BIT_INODE
 409 is not defined.
 410 .It 64-bit
 411 64-bit inode values are enabled, and the expanded structures involving the
 412 .Vt ino_t
 413 type are in use.
 414 The macro
 415 .Dv _DARWIN_FEATURE_64_BIT_INODE
 416 is defined, and loader symbols will contain the
 417 .Li $INODE64
 418 suffix.
 419 .It 64-bit-only
 420 Like 64-bit, except loader symbols do not have the
 421 .Li $INODE64
 422 suffix.
 423 .It Em (error)
 424 A compile time error is generated.
 425 .El
 426 .Pp
 427 Due to the increased benefits of the larger structure, it is highly
 428 recommended that developers not define
 429 .Dv _DARWIN_NO_64_BIT_INODE
 430 and make use of
 431 .Dv _DARWIN_USE_64_BIT_INODE
 432 when targeting Mac OSX 10.5.
 433 .Pp
 434 In addition to the $INODE64 suffixed symbols, variants suffixed with 64 are
 435 also available for related functions.  These functions were provided as a way
 436 for developers to use the updated structures in code that also made use of
 437 the legacy structures.  The enlarged stat structures were also prefixed with
 438 64 to distinguish them from their legacy variants.  These functions have been
 439 deprecated and should be avoided.
 440 .Sh RETURN VALUES
 441 Upon successful completion a value of 0 is returned.
 442 Otherwise, a value of -1 is returned and
 443 .Va errno
 444 is set to indicate the error.
 445 .Sh COMPATIBILITY
 446 Previous versions of the system used different types for the
 447 .Li st_dev ,
 448 .Li st_uid ,
 449 .Li st_gid ,
 450 .Li st_rdev ,
 451 .Li st_size ,
 452 .Li st_blksize
 453 and
 454 .Li st_blocks
 455 fields.
 456 .Sh ERRORS
 457 .Bl -tag -width Er
 458 The
 459 .Fn fstat
 460 system call will fail if:
 461 .\" ===========
 462 .It Bq Er EBADF
 463 .Fa fildes
 464 is not a valid open file descriptor.
 465 .\" ===========
 466 .It Bq Er EFAULT
 467 .Fa Sb
 468 points to an invalid address.
 469 .\" ===========
 470 .It Bq Er EIO
 471 An I/O error occurs while reading from or writing to the file system.
 472 .El
 473 .Pp
 474 The
 475 .Fn lstat
 476 and
 477 .Fn stat
 478 system calls will fail if:
 479 .Bl -tag -width Er
 480 .\" ===========
 481 .It Bq Er EACCES
 482 Search permission is denied for a component of the path prefix.
 483 .\" ===========
 484 .It Bq Er EFAULT
 485 .Fa Sb
 486 or
 487 .Em name
 488 points to an invalid address.
 489 .\" ===========
 490 .It Bq Er EIO
 491 An I/O error occurs while reading from or writing to the file system.
 492 .\" ===========
 493 .It Bq Er ELOOP
 494 Too many symbolic links are encountered in translating the pathname.
 495 This is taken to be indicative of a looping symbolic link.
 496 .\" ===========
 497 .It Bq Er ENAMETOOLONG
 498 A component of a pathname exceeds
 499 .Dv {NAME_MAX}
 500 characters, or an entire path name exceeds
 501 .Dv {PATH_MAX}
 502 characters.
 503 .\" ===========
 504 .It Bq Er ENOENT
 505 The named file does not exist.
 506 .\" ===========
 507 .It Bq Er ENOTDIR
 508 A component of the path prefix is not a directory.
 509 .El
 510 .Pp
 511 The
 512 .Fn fstat ,
 513 .Fn lstat ,
 514 and
 515 .Fn stat
 516 system calls will fail if:
 517 .Bl -tag -width Er
 518 .\" ===========
 519 .It Bq Er EOVERFLOW
 520 The file size in bytes
 521 or the number of blocks allocated to the file
 522 or the file serial number cannot be represented correctly
 523 in the structure pointed to by
 524 .Fa buf .
 525 .El
 526 .Pp
 527 In addition to the errors returned by the
 528 .Fn stat
 529 and
 530 .Fn lstat ,
 531 .Fn fstatat
 532 may fail if:
 533 .Bl -tag -width Er
 534 .It Bq Er EBADF
 535 The
 536 .Fa path
 537 argument does not specify an absolute path and the
 538 .Fa fd
 539 argument is neither
 540 .Dv AT_FDCWD
 541 nor a valid file descriptor open for searching.
 542 .It Bq Er EINVAL
 543 The value of the
 544 .Fa flag
 545 argument is not valid.
 546 .It Bq Er ENOTDIR
 547 The
 548 .Fa path
 549 argument is not an absolute path and
 550 .Fa fd
 551 is neither
 552 .Dv AT_FDCWD
 553 nor a file descriptor associated with a directory.
 554 .El
 555 .Sh CAVEATS
 556 The file generation number,
 557 .Fa st_gen ,
 558 is only available to the super-user.
 559 .br
 560 The fields in the stat structure currently marked
 561 .Fa st_spare1 ,
 562 .Fa st_spare2 ,
 563 and
 564 .Fa st_spare3
 565 are present in preparation for inode time stamps expanding
 566 to 64 bits.  This, however, can break certain programs that
 567 depend on the time stamps being contiguous (in calls to
 568 .Xr utimes 2 ) .
 569 .Sh TRANSITIONAL DESCRIPTION (NOW DEPRECATED)
 570 The
 571 .Fa fstat64 ,
 572 .Fa lstat64
 573 and
 574 .Fa stat64
 575 routines are equivalent to their corresponding non-64-suffixed routine,
 576 when 64-bit inodes are in effect.
 577 They were added before there was support for the symbol variants, and so are
 578 now deprecated.
 579 Instead of using these, set the
 580 .Dv _DARWIN_USE_64_BIT_INODE
 581 macro before including header files to force 64-bit inode support.
 582 .Pp
 583 The
 584 .Fa stat64
 585 structure used by these deprecated routines is the same as the
 586 .Fa stat
 587 structure when 64-bit inodes are in effect (see above).
 588 .Sh SEE ALSO
 589 .Xr chflags 2 ,
 590 .Xr chmod 2 ,
 591 .Xr chown 2 ,
 592 .Xr utimes 2 ,
 593 .Xr compat 5 ,
 594 .Xr statfs 2 ,
 595 .Xr symlink 7
 596 .Sh BUGS
 597 Applying
 598 .Xr fstat
 599 to a socket (and thus to a pipe)
 600 returns a zero'd buffer,
 601 except for the blocksize field,
 602 and a unique device and inode number.
 603 .Sh STANDARDS
 604 The
 605 .Fn stat
 606 and
 607 .Fn fstat
 608 function calls are expected to conform to
 609 .St -p1003.1-88 .
 610 The
 611 .Fn fstatat
 612 system call is expected to conform to POSIX.1-2008 .
 613 .Sh HISTORY
 614 An
 615 .Fn lstat
 616 function call appeared in
 617 .Bx 4.2 .
 618 The
 619 .Fn stat64 ,
 620 .Fn fstat64 ,
 621 and
 622 .Fn lstat64
 623 system calls first appeared in Mac OS X 10.5 (Leopard) and are now deprecated
 624 in favor of the corresponding symbol variants.
 625 The
 626 .Fn fstatat
 627 system call appeared in OS X 10.10