STAT(2)                    System calls                   STAT(2)



NAME

       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, except in the case of a sym-
       bolic link, where the link itself is stat-ed, not the file
       that it refers to.

       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_size gives the size of the file (if it  is  a
       regular file or a symlink) in bytes. The size of a symlink
       is the length of the pathname it contains, without  trail-
       ing NUL.




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STAT(2)                    System calls                   STAT(2)


       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-
       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
       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_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?

              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:

       l l l.  S_IFMT    0170000   bitmask for the file type bit-
       fields S_IFSOCK  0140000   socket S_IFLNK   0120000   sym-
       bolic      link      S_IFREG   0100000   regular      file
       S_IFBLK   0060000   block                           device
       S_IFDIR   0040000   directory  S_IFCHR   0020000   charac-
       ter            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



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STAT(2)                    System calls                   STAT(2)


       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    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,



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STAT(2)                    System calls                   STAT(2)


       X/OPEN, BSD 4.3.  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 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.
       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:

       l   l   l   l   l.    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  spe-
       cial   (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



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STAT(2)                    System calls                   STAT(2)


       cache  this  file  (SunOS)                     On directo-
       ries:     restricted     deletion     flag     (SVID-v4.2)
       0400 S_ISGID        002000    set  group  ID  on execution
       (V7)                     for directories: use  BSD  seman-
       tics         for         propagation         of        gid
       0400 S_ENFMT        002000    SysV file  locking  enforce-
       ment (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.



SEE ALSO

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









































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