bsd/man/man2/stat.2

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  34 .\"     @(#)stat.2      8.3 (Berkeley) 4/19/94
  35 .\"
  36 .Dd April 19, 1994
  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 .Nd get file status
  47 .Sh SYNOPSIS
  48 .Fd #include <sys/stat.h>
  49 .Ft int
  50 .Fo fstat
  51 .Fa "int fildes"
  52 .Fa "struct stat *buf"
  53 .Fc
  54 .Ft int
  55 .Fo fstat64
  56 .Fa "int fildes"
  57 .Fa "struct stat64 *buf"
  58 .Fc
  59 .Ft int
  60 .Fo lstat
  61 .Fa "const char *restrict path"
  62 .Fa "struct stat *restrict buf"
  63 .Fc
  64 .Ft int
  65 .Fo lstat64
  66 .Fa "const char *restrict path"
  67 .Fa "struct stat64 *restrict buf"
  68 .Fc
  69 .Ft int
  70 .Fo stat
  71 .Fa "const char *restrict path"
  72 .Fa "struct stat *restrict buf"
  73 .Fc
  74 .Ft int
  75 .Fo stat64
  76 .Fa "const char *restrict path"
  77 .Fa "struct stat64 *restrict buf"
  78 .Fc
  79 .Sh DESCRIPTION
  80 The
  81 .Fn stat
  82 family of functions and their 64 bit variants obtain information about a file. The
  83 .Fn stat
  84 function obtains information about the file pointed to by
  85 .Fa path .
  86 Read, write or execute
  87 permission of the named file is not required, but all directories
  88 listed in the path name leading to the file must be searchable.
  89 .Pp
  90 .Fn Lstat
  91 is like
  92 .Fn stat
  93 except in the case where the named file is a symbolic link,
  94 in which case
  95 .Fn lstat
  96 returns information about the link,
  97 while
  98 .Fn stat
  99 returns information about the file the link references.
 100 Unlike other filesystem objects,
 101 symbolic links do not have an owner, group, access mode, times, etc.
 102 Instead, these attributes are taken from the directory that
 103 contains the link.
 104 The only attributes returned from an
 105 .Fn lstat
 106 that refer to the symbolic link itself are the file type (S_IFLNK),
 107 size, blocks, and link count (always 1).
 108 .Pp
 109 The
 110 .Fn fstat
 111 obtains the same information about an open file
 112 known by the file descriptor
 113 .Fa fildes .
 114 .Pp
 115 The
 116 .Fa buf
 117 argument is a pointer to a
 118 .Fa stat
 119 or
 120 .Fa stat64
 121 structure
 122 as defined by
 123 .Aq Pa sys/stat.h
 124 (both shown below)
 125 and into which information is placed concerning the file.
 126 .Bd -literal
 127 struct stat {
 128     dev_t    st_dev;    /* device inode resides on */
 129     ino_t    st_ino;    /* inode's number */
 130     mode_t   st_mode;   /* inode protection mode */
 131     nlink_t  st_nlink;  /* number or hard links to the file */
 132     uid_t    st_uid;    /* user-id of owner */
 133     gid_t    st_gid;    /* group-id of owner */
 134     dev_t    st_rdev;   /* device type, for special file inode */
 135     struct timespec st_atimespec;  /* time of last access */
 136     struct timespec st_mtimespec;  /* time of last data modification */
 137     struct timespec st_ctimespec;  /* time of last file status change */
 138     off_t    st_size;   /* file size, in bytes */
 139     quad_t   st_blocks; /* blocks allocated for file */
 140     u_long   st_blksize;/* optimal file sys I/O ops blocksize */
 141     u_long   st_flags;  /* user defined flags for file */
 142     u_long   st_gen;    /* file generation number */
 143 };
 144
 145
 146 struct stat64 {
 147     dev_t           st_dev;           /* ID of device containing file */
 148     mode_t          st_mode;          /* Mode of file (see below) */
 149     nlink_t         st_nlink;         /* Number of hard links */
 150     ino64_t         st_ino;          /* File serial number */
 151     uid_t           st_uid;           /* User ID of the file */
 152     gid_t           st_gid;           /* Group ID of the file */
 153     dev_t           st_rdev;          /* Device ID */
 154     struct timespec st_atimespec;     /* time of last access */
 155     struct timespec st_mtimespec;     /* time of last data modification */
 156     struct timespec st_ctimespec;     /* time of last status change */
 157     struct timespec st_birthtimespec; /* time of file creation(birth) */
 158     off_t           st_size;          /* file size, in bytes */
 159     blkcnt_t        st_blocks;        /* blocks allocated for file */
 160     blksize_t       st_blksize;       /* optimal blocksize for I/O */
 161     uint32_t        st_flags;         /* user defined flags for file */
 162     uint32_t        st_gen;           /* file generation number */
 163     int32_t         st_lspare;        /* RESERVED: DO NOT USE! */
 164     int64_t         st_qspare[2];     /* RESERVED: DO NOT USE! */
 165 };
 166
 167
 168 .Ed
 169 .Pp
 170 The time-related fields of
 171 .Fa struct stat
 172 and
 173 .Fa struct stat64
 174 are as follows:
 175 .Bl -tag -width XXXst_birthtime
 176 .It st_atime
 177 Time when file data last accessed.
 178 Changed by the
 179 .Xr mknod 2 ,
 180 .Xr utimes 2
 181 and
 182 .Xr read 2
 183 system calls.
 184 .It st_mtime
 185 Time when file data last modified.
 186 Changed by the
 187 .Xr mknod 2 ,
 188 .Xr utimes 2
 189 and
 190 .Xr write 2
 191 system calls.
 192 .It st_ctime
 193 Time when file status was last changed (inode data modification).
 194 Changed by the
 195 .Xr chmod 2 ,
 196 .Xr chown 2 ,
 197 .Xr link 2 ,
 198 .Xr mknod 2 ,
 199 .Xr rename 2 ,
 200 .Xr unlink 2 ,
 201 .Xr utimes 2
 202 and
 203 .Xr write 2
 204 system calls.
 205 .It st_birthtime
 206 Time of file creation. Only set once when the file is created. This field is
 207 only available in the 64 bit variants. On filesystems where birthtime is
 208 not available, this field holds the
 209 .Fa ctime
 210 instead.
 211 .El
 212 .Pp
 213 The size-related fields of the structures are as follows:
 214 .Bl -tag -width XXXst_blksize
 215 .It st_blksize
 216 The optimal I/O block size for the file.
 217 .It st_blocks
 218 The actual number of blocks allocated for the file in 512-byte units.
 219 As short symbolic links are stored in the inode, this number may
 220 be zero.
 221 .El
 222 .Pp
 223 The status information word
 224 .Fa st_mode
 225 has the following bits:
 226 .Bd -literal
 227 #define S_IFMT 0170000           /* type of file */
 228 #define        S_IFIFO  0010000  /* named pipe (fifo) */
 229 #define        S_IFCHR  0020000  /* character special */
 230 #define        S_IFDIR  0040000  /* directory */
 231 #define        S_IFBLK  0060000  /* block special */
 232 #define        S_IFREG  0100000  /* regular */
 233 #define        S_IFLNK  0120000  /* symbolic link */
 234 #define        S_IFSOCK 0140000  /* socket */
 235 #define        S_IFWHT  0160000  /* whiteout */
 236 #define S_ISUID 0004000  /* set user id on execution */
 237 #define S_ISGID 0002000  /* set group id on execution */
 238 #define S_ISVTX 0001000  /* save swapped text even after use */
 239 #define S_IRUSR 0000400  /* read permission, owner */
 240 #define S_IWUSR 0000200  /* write permission, owner */
 241 #define S_IXUSR 0000100  /* execute/search permission, owner */
 242 .Ed
 243 .Pp
 244 For a list of access modes, see
 245 .Aq Pa sys/stat.h ,
 246 .Xr access 2
 247 and
 248 .Xr chmod 2 .
 249 .Pp
 250 For a list of the file flags in the
 251 .Fa st_flags
 252 field, see
 253 .Aq Pa sys/stat.h
 254 and
 255 .Xr chflags 2 .
 256 .Sh RETURN VALUES
 257 Upon successful completion a value of 0 is returned.
 258 Otherwise, a value of -1 is returned and
 259 .Va errno
 260 is set to indicate the error.
 261 .Sh COMPATIBILITY
 262 Previous versions of the system used different types for the
 263 .Li st_dev ,
 264 .Li st_uid ,
 265 .Li st_gid ,
 266 .Li st_rdev ,
 267 .Li st_size ,
 268 .Li st_blksize
 269 and
 270 .Li st_blocks
 271 fields.
 272 .Sh ERRORS
 273 .Bl -tag -width Er
 274 The
 275 .Fn fstat
 276 system call will fail if:
 277 .\" ===========
 278 .It Bq Er EBADF
 279 .Fa fildes
 280 is not a valid open file descriptor.
 281 .\" ===========
 282 .It Bq Er EFAULT
 283 .Fa Sb
 284 points to an invalid address.
 285 .\" ===========
 286 .It Bq Er EIO
 287 An I/O error occurs while reading from or writing to the file system.
 288 .El
 289 .Pp
 290 The
 291 .Fn lstat
 292 and
 293 .Fn stat
 294 system calls will fail if:
 295 .Bl -tag -width Er
 296 .\" ===========
 297 .It Bq Er EACCES
 298 Search permission is denied for a component of the path prefix.
 299 .\" ===========
 300 .It Bq Er EFAULT
 301 .Fa Sb
 302 or
 303 .Em name
 304 points to an invalid address.
 305 .\" ===========
 306 .It Bq Er EIO
 307 An I/O error occurs while reading from or writing to the file system.
 308 .\" ===========
 309 .It Bq Er ELOOP
 310 Too many symbolic links are encountered in translating the pathname.
 311 This is taken to be indicative of a looping symbolic link.
 312 .\" ===========
 313 .It Bq Er ENAMETOOLONG
 314 A component of a pathname exceeds
 315 .Dv {NAME_MAX}
 316 characters, or an entire path name exceeds
 317 .Dv {PATH_MAX}
 318 characters.
 319 .\" ===========
 320 .It Bq Er ENOENT
 321 The named file does not exist.
 322 .\" ===========
 323 .It Bq Er ENOTDIR
 324 A component of the path prefix is not a directory.
 325 .El
 326 .Pp
 327 The
 328 .Fn fstat ,
 329 .Fn lstat ,
 330 and
 331 .Fn stat
 332 system calls will fail if:
 333 .Bl -tag -width Er
 334 .\" ===========
 335 .It Bq Er EOVERFLOW
 336 The file size in bytes
 337 or the number of blocks allocated to the file
 338 or the file serial number cannot be represented correctly
 339 in the structure pointed to by
 340 .Fa buf .
 341 .El
 342 .Sh CAVEATS
 343 The file generation number,
 344 .Fa st_gen ,
 345 is only available to the super-user.
 346 .br
 347 The fields in the stat structure currently marked
 348 .Fa st_spare1 ,
 349 .Fa st_spare2 ,
 350 and
 351 .Fa st_spare3
 352 are present in preparation for inode time stamps expanding
 353 to 64 bits.  This, however, can break certain programs that
 354 depend on the time stamps being contiguous (in calls to
 355 .Xr utimes 2 ) .
 356 .Sh LEGACY SYNOPSIS
 357 .Fd #include <sys/types.h>
 358 .Fd #include <sys/stat.h>
 359 .Pp
 360 The include file
 361 .In sys/types.h
 362 is necessary.
 363 .Sh SEE ALSO
 364 .Xr chflags 2 ,
 365 .Xr chmod 2 ,
 366 .Xr chown 2 ,
 367 .Xr utimes 2 ,
 368 .Xr compat 5 ,
 369 .Xr symlink 7
 370 .Sh BUGS
 371 Applying
 372 .Xr fstat
 373 to a socket (and thus to a pipe)
 374 returns a zero'd buffer,
 375 except for the blocksize field,
 376 and a unique device and inode number.
 377 .Sh STANDARDS
 378 The
 379 .Fn stat
 380 and
 381 .Fn fstat
 382 function calls are expected to conform to
 383 .St -p1003.1-88 .
 384 .Sh HISTORY
 385 An
 386 .Fn lstat
 387 function call appeared in
 388 .Bx 4.2 .
 389 The
 390 .Fn stat64 ,
 391 .Fn fstat64 ,
 392 and
 393 .Fn lstat64
 394 system calls first appeared in Mac OS X 10.5 (Leopard).