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NAME

       stat, fstat, lstat - get file status

SYNOPSIS

       #include <sys/types.h>
       #include <sys/stat.h>
       #include <unistd.h>

       int stat(const char *path, struct stat *buf);
       int fstat(int filedes, struct stat *buf);
       int lstat(const char *path, struct stat *buf);

DESCRIPTION

       These  functions  return  information about a file.  No permissions are
       required on the file itself, but — in the case of stat() and lstat()  —
       execute  (search)  permission  is required on all of the directories in
       path that lead to the file.

       stat() stats the file pointed to by path and fills in buf.

       lstat() is identical to stat(), except that if path is a symbolic link,
       then the link itself is stat-ed, not the file that it refers to.

       fstat()  is  identical to stat(), except that the file to be stat-ed is
       specified by the file descriptor filedes.

       All of these system calls return a stat structure, which  contains  the
       following fields:

          struct stat {
              dev_t     st_dev;     /* ID of device containing file */
              ino_t     st_ino;     /* inode number */
              mode_t    st_mode;    /* protection */
              nlink_t   st_nlink;   /* number of hard links */
              uid_t     st_uid;     /* user ID of owner */
              gid_t     st_gid;     /* group ID of owner */
              dev_t     st_rdev;    /* device ID (if special file) */
              off_t     st_size;    /* total size, in bytes */
              blksize_t st_blksize; /* blocksize for filesystem I/O */
              blkcnt_t  st_blocks;  /* number of blocks allocated */
              time_t    st_atime;   /* time of last access */
              time_t    st_mtime;   /* time of last modification */
              time_t    st_ctime;   /* time of last status change */
          };

       The st_dev field describes the device on which this file resides.

       The   st_rdev  field  describes  the  device  that  this  file  (inode)
       represents.

       The st_size field gives the size of the file (if it is a  regular  file
       or  a  symbolic link) in bytes.  The size of a symlink is the length of
       the pathname it contains, without trailing NUL.

       The st_blocks field indicates the number of  blocks  allocated  to  the
       file,  512-byte  units.   (This  may  be  smaller than st_size/512, for
       example, when the file has holes.)

       The st_blksize field gives the "preferred" blocksize for efficient file
       system  I/O.   (Writing  to  a  file  in  smaller  chunks  may cause an
       inefficient read-modify-rewrite.)

       Not all of the Linux filesystems implement  all  of  the  time  fields.
       Some  file system types allow mounting in such a way that file accesses
       do not cause an  update  of  the  st_atime  field.  (See  ‘noatime’  in
       mount(8).)

       The  field  st_atime  is  changed  by file accesses, e.g. by execve(2),
       mknod(2), pipe(2), utime(2) and read(2)  (of  more  than  zero  bytes).
       Other routines, like mmap(2), may or may not update st_atime.

       The  field st_mtime is changed by file modifications, e.g. by mknod(2),
       truncate(2),  utime(2)  and  write(2)  (of  more  than   zero   bytes).
       Moreover,  st_mtime  of  a  directory  is  changed  by  the creation or
       deletion of files in that directory.  The st_mtime field is not changed
       for changes in owner, group, hard link count, or mode.

       The   field  st_ctime  is  changed  by  writing  or  by  setting  inode
       information (i.e., owner, group, link count, mode, etc.).

       The following POSIX macros are defined to check the file type using the
       st_mode field:

              S_ISREG(m)  is it a regular file?

              S_ISDIR(m)  directory?

              S_ISCHR(m)  character device?

              S_ISBLK(m)  block device?

              S_ISFIFO(m) FIFO (named pipe)?

              S_ISLNK(m)  symbolic link? (Not in POSIX.1-1996.)

              S_ISSOCK(m) socket? (Not in POSIX.1-1996.)

       The following flags are defined for the st_mode field:

       S_IFMT     0170000   bitmask for the file type bitfields
       S_IFSOCK   0140000   socket
       S_IFLNK    0120000   symbolic link
       S_IFREG    0100000   regular file
       S_IFBLK    0060000   block device
       S_IFDIR    0040000   directory
       S_IFCHR    0020000   character device
       S_IFIFO    0010000   FIFO
       S_ISUID    0004000   set UID bit
       S_ISGID    0002000   set-group-ID bit (see below)
       S_ISVTX    0001000   sticky bit (see below)
       S_IRWXU    00700     mask for file owner permissions
       S_IRUSR    00400     owner has read permission
       S_IWUSR    00200     owner has write permission
       S_IXUSR    00100     owner has execute permission
       S_IRWXG    00070     mask for group permissions
       S_IRGRP    00040     group has read permission
       S_IWGRP    00020     group has write permission
       S_IXGRP    00010     group has execute permission
       S_IRWXO    00007     mask for permissions for others (not in group)
       S_IROTH    00004     others have read permission
       S_IWOTH    00002     others have write permission
       S_IXOTH    00001     others have execute permission

       The  set-group-ID  bit  (S_ISGID)  has  several  special  uses.   For a
       directory it indicates that BSD  semantics  is  to  be  used  for  that
       directory:  files  created  there  inherit  their  group  ID  from  the
       directory, not from the effective group ID of the creating process, and
       directories  created  there  will  also get the S_ISGID bit set.  For a
       file that does not have the group execution bit (S_IXGRP) set, the set-
       group-ID bit indicates mandatory file/record locking.

       The  ‘sticky’  bit  (S_ISVTX)  on a directory means that a file in that
       directory can be renamed or deleted only by the owner of the  file,  by
       the owner of the directory, and by a privileged process.

LINUX NOTES

       Since  kernel 2.5.48, the stat structure supports nanosecond resolution
       for the three file timestamp  fields.   Glibc  exposes  the  nanosecond
       component of each field using names either of the form st_atim.tv_nsec,
       if the _BSD_SOURCE or _SVID_SOURCE feature test macro is defined, or of
       the  form st_atimensec, if neither of these macros is defined.  On file
       systems that do not support  sub-second  timestamps,  these  nanosecond
       fields are returned with the value 0.

RETURN VALUE

       On  success,  zero is returned.  On error, -1 is returned, and errno is
       set appropriately.

ERRORS

       EACCES Search permission is denied for one of the  directories  in  the
              path prefix of path.  (See also path_resolution(2).)

       EBADF  filedes is bad.

       EFAULT Bad address.

       ELOOP  Too many symbolic links encountered while traversing the path.

       ENAMETOOLONG
              File name too long.

       ENOENT A  component  of the path path does not exist, or the path is an
              empty string.

       ENOMEM Out of memory (i.e. kernel memory).

       ENOTDIR
              A component of the path is not a directory.

CONFORMING TO

       The stat() and fstat() calls conform  to  SVr4,  SVID,  POSIX,  X/OPEN,
       4.3BSD.   The lstat() call conforms to 4.3BSD and SVr4.  SVr4 documents
       additional fstat() error  conditions  EINTR,  ENOLINK,  and  EOVERFLOW.
       SVr4  documents  additional  stat() and lstat() error conditions EINTR,
       EMULTIHOP, ENOLINK, and EOVERFLOW.  Use of the st_blocks and st_blksize
       fields  may  be  less  portable. (They were introduced in BSD.  Are not
       specified by POSIX. The interpretation  differs  between  systems,  and
       possibly on a single system when NFS mounts are involved.)

       POSIX  does  not  describe  the  S_IFMT,  S_IFSOCK,  S_IFLNK,  S_IFREG,
       S_IFBLK, S_IFDIR, S_IFCHR, S_IFIFO, S_ISVTX bits, but  instead  demands
       the  use  of the macros S_ISDIR(), etc. The S_ISLNK and S_ISSOCK macros
       are not in POSIX.1-1996, but both will be in the next  POSIX  standard;
       the former is from SVID 4v2, the latter from SUSv2.

       Unix V7 (and later systems) had S_IREAD, S_IWRITE, S_IEXEC, where POSIX
       prescribes the synonyms S_IRUSR, S_IWUSR, S_IXUSR.

OTHER SYSTEMS

       Values that have been (or are) in use on various systems:

       hex    name       ls   octal    description

       f000   S_IFMT          170000   mask for file type
       0000                   000000   SCO out-of-service inode, BSD unknown type
                                       SVID-v2 and XPG2 have both 0 and 0100000 for ordinary file
       1000   S_IFIFO    p|   010000   FIFO (named pipe)
       2000   S_IFCHR    c    020000   character special (V7)
       3000   S_IFMPC         030000   multiplexed character special (V7)
       4000   S_IFDIR    d/   040000   directory (V7)
       5000   S_IFNAM         050000   XENIX named special file
                                       with two subtypes, distinguished by st_rdev values 1, 2:
       0001   S_INSEM    s    000001   XENIX semaphore subtype of IFNAM
       0002   S_INSHD    m    000002   XENIX shared data subtype of IFNAM
       6000   S_IFBLK    b    060000   block special (V7)
       7000   S_IFMPB         070000   multiplexed block special (V7)
       8000   S_IFREG    -    100000   regular (V7)
       9000   S_IFCMP         110000   VxFS compressed
       9000   S_IFNWK    n    110000   network special (HP-UX)
       a000   S_IFLNK    l@   120000   symbolic link (BSD)
       b000   S_IFSHAD        130000   Solaris shadow inode for ACL (not seen by userspace)
       c000   S_IFSOCK   s=   140000   socket (BSD; also "S_IFSOC" on VxFS)
       d000   S_IFDOOR   D>   150000   Solaris door
       e000   S_IFWHT    w%   160000   BSD whiteout (not used for inode)

       0200   S_ISVTX         001000   ‘sticky bit’: save swapped text even after use (V7)
                                       reserved (SVID-v2)
                                       On non-directories: don’t cache this file (SunOS)
                                       On directories: restricted deletion flag (SVID-v4.2)
       0400   S_ISGID         002000   set-group-ID on execution (V7)
                                       for directories: use BSD semantics for propagation of GID
       0400   S_ENFMT         002000   SysV file locking enforcement (shared with S_ISGID)
       0800   S_ISUID         004000   set-user-ID on execution (V7)
       0800   S_CDF           004000   directory is a context dependent file (HP-UX)

       A sticky command appeared in Version 32V AT&T UNIX.

SEE ALSO

       chmod(2), chown(2), readlink(2), utime(2), capabilities(7)