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