stat


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) 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 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) repre-
       sents.

       Not all of the Linux file systems implement all  of  the  time  fields.
       Some  file  system  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 dele-
       tion 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 informa-
       tion (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

       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 appropriately.

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  introduced  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
       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 com-
       ponent 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

       #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_FAILURE);
           }

           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));



Linux                             2009-09-30                           STAT(2)
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