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