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STAT(2)                    Linux Programmer's Manual                   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 *path, struct stat *buf);
       int fstat(int fd, struct stat *buf);
       int lstat(const char *path, struct stat *buf);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       lstat(): _BSD_SOURCE || _XOPEN_SOURCE >= 500

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) permis-
       sion 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 fd.

       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 file system I/O */
               blkcnt_t  st_blocks;  /* number of 512B 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  major(3)
       and minor(3) macros may be useful to decompose the device ID in this field.)

       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 a trailing null byte.

       The  st_blocks field indicates the number of blocks allocated to the file, 512-byte
       units.  (This may be smaller than st_size/512 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 file systems implement all of the time fields.  Some file sys-
       tem  types  allow mounting in such a way that file and/or directory accesses do not
       cause an update of the st_atime field.  (See noatime, nodiratime, and  relatime  in
       mount(8),  and  related  information  in  mount(2).)   In addition, st_atime is not
       updated if a file is opened with the O_NOATIME; see open(2).

       The field st_atime  is  changed  by  file  accesses,  for  example,  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,  for  example,  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   bit mask for the file type bit fields
           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  indi-
       cates  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.

RETURN VALUE
       On success, zero is returned.  On error, -1 is returned, and errno is set appropri-
       ately.

ERRORS
       EACCES Search permission is denied for one of the directories in the path prefix of
              path.  (See also path_resolution(7).)

       EBADF  fd is bad.

       EFAULT Bad address.

       ELOOP  Too many symbolic links encountered while traversing the path.

       ENAMETOOLONG
              File name too long.

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

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

       ENOTDIR
              A component of the path prefix of path is not a directory.

       EOVERFLOW
              (stat())  path  refers  to  a  file  whose size cannot be represented in the
              type       off_t.  This can occur when an application compiled on  a  32-bit
              platform  without  -D_FILE_OFFSET_BITS=64  calls stat() on a file whose size
              exceeds (2<<31)-1 bits.

CONFORMING TO
       These system calls conform to SVr4, 4.3BSD, POSIX.1-2001.

       Use of the st_blocks and st_blksize fields may be less portable.  (They were intro-
       duced in BSD.  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 are present in POSIX.1-2001; the former is from SVID 4, 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   System V 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.

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.

       On Linux, lstat() will generally not trigger  automounter  action,  whereas  stat()
       will.

       For  most  files under the /proc directory, stat() does not return the file size in
       the st_size field; instead the field is returned with the value 0.

   Underlying kernel interface
       Over time, increases in the size of the stat structure have led to three successive
       versions of stat(): sys_stat() (slot __NR_oldstat), sys_newstat() (slot __NR_stat),
       and sys_stat64() (new in kernel 2.4; slot __NR_stat64).  The glibc  stat()  wrapper
       function hides these details from applications, invoking the most recent version of
       the system call provided by the kernel, and repacking the returned  information  if
       required for old binaries.  Similar remarks apply for fstat() and lstat().

EXAMPLE
       The  following  program  calls  stat() and displays selected fields in the returned
       stat structure.

       #include <sys/types.h>
       #include <sys/stat.h>
       #include <time.h>
       #include <stdio.h>
       #include <stdlib.h>

       int
       main(int argc, char *argv[])
       {
           struct stat sb;

           if (argc != 2) {
               fprintf(stderr, "Usage: %s <pathname>\n", argv[0]);
               exit(EXIT_FAILURE);
           }

           if (stat(argv[1], &sb) == -1) {
               perror("stat");
               exit(EXIT_SUCCESS);
           }

           printf("File type:                ");

           switch (sb.st_mode & S_IFMT) {
           case S_IFBLK:  printf("block device\n");            break;
           case S_IFCHR:  printf("character device\n");        break;
           case S_IFDIR:  printf("directory\n");               break;
           case S_IFIFO:  printf("FIFO/pipe\n");               break;
           case S_IFLNK:  printf("symlink\n");                 break;
           case S_IFREG:  printf("regular file\n");            break;
           case S_IFSOCK: printf("socket\n");                  break;
           default:       printf("unknown?\n");                break;
           }

           printf("I-node number:            %ld\n", (long) sb.st_ino);

           printf("Mode:                     %lo (octal)\n",
                   (unsigned long) sb.st_mode);

           printf("Link count:               %ld\n", (long) sb.st_nlink);
           printf("Ownership:                UID=%ld   GID=%ld\n",
                   (long) sb.st_uid, (long) sb.st_gid);

           printf("Preferred I/O block size: %ld bytes\n",
                   (long) sb.st_blksize);
           printf("File size:                %lld bytes\n",
                   (long long) sb.st_size);
           printf("Blocks allocated:         %lld\n",
                   (long long) sb.st_blocks);

           printf("Last status change:       %s", ctime(&sb.st_ctime));
           printf("Last file access:         %s", ctime(&sb.st_atime));
           printf("Last file modification:   %s", ctime(&sb.st_mtime));

           exit(EXIT_SUCCESS);
       }

SEE ALSO
       access(2), chmod(2), chown(2), fstatat(2), readlink(2), utime(2),  capabilities(7),
       symlink(7)

COLOPHON
       This page is part of release 3.22 of the Linux man-pages project.  A description of
       the project, and information about reporting bugs, can be found at  http://www.ker-
       nel.org/doc/man-pages/.



Linux                             2009-04-21                           STAT(2)

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