stat, fstat, lstat - get file status


SYNOPSIS

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

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


DESCRIPTION

       These  functions  return  information  about the specified
       file.  You do not need any access rights to  the  file  to
       get  this  information  but  you need search rights to all
       directories named in the path leading to the file.

       stat stats the file pointed to by file_name and  fills  in
       buf.

       lstat  is identical to stat, only the link itself is stat-
       ed, not the file that is obtained by tracing the links.

       fstat is identical to stat, only the open file pointed  to
       by  filedes (as returned by open(2)) is stated in place of
       file_name.


       They all return a stat structure, which contains the  fol­
       lowing fields:

              struct stat
              {
                  dev_t         st_dev;      /* device */
                  ino_t         st_ino;      /* inode */
                  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 type (if inode device) */
                  off_t         st_size;     /* total size, in bytes */
                  unsigned long st_blksize;  /* blocksize for filesystem I/O */
                  unsigned long 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 change */
              };

       The value st_blocks gives the size of the file in 512-byte
       blocks.  The value st_blksize gives the "preferred" block­
       size for efficient file system I/O.  (Writing to a file in
       smaller  chunks  may  cause  an  inefficient  read-modify-
       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
       exec(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:

              S_ISLNK(m)  is it a symbolic link?

              S_ISREG(m)  regular file?

              S_ISDIR(m)  directory?

              S_ISCHR(m)  character device?

              S_ISBLK(m)  block device?

              S_ISFIFO(m) fifo?

              S_ISSOCK(m) socket?

       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 GID 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_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 permisson
       S_IXOTH    00001     others have execute permission

       The  set GID 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 gid 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, it 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 root.


RETURN VALUE

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


ERRORS

       EBADF  filedes is bad.

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

       ENOTDIR
              A component of the path is not a directory.

       ELOOP  Too  many symbolic links encountered while travers­
              ing the path.

       EFAULT Bad address.

       EACCES Permission denied.

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

       ENAMETOOLONG
              File name too long.


CONFORMING TO

       The stat and fstat calls conform  to  SVr4,  SVID,  POSIX,
       X/OPEN,  BSD  4.3.   The lstat call conforms to 4.3BSD and
       stat and lstat error conditions EACCES, EINTR,  EMULTIHOP,
       ENOLINK,  and EOVERFLOW.  Use of the st_blocks and st_blk­
       size fields may be less portable. (They were introduced in
       BSD.   Are not specified by POSIX. The interpretation dif­
       fers 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.
       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 w/ 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.

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