stat(2) — Linux manual page

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | STANDARDS | HISTORY | EXAMPLES | SEE ALSO

stat(2)                    System Calls Manual                   stat(2)

NAME         top

       stat, fstat, lstat, fstatat - get file status

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #include <sys/stat.h>

       int stat(const char *restrict pathname,
                struct stat *restrict statbuf);
       int fstat(int fd, struct stat *statbuf);
       int lstat(const char *restrict pathname,
                struct stat *restrict statbuf);

       #include <fcntl.h>           /* Definition of AT_* constants */
       #include <sys/stat.h>

       int fstatat(int dirfd, const char *restrict pathname,
                struct stat *restrict statbuf, int flags);

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

       lstat():
           /* Since glibc 2.20 */ _DEFAULT_SOURCE
               || _XOPEN_SOURCE >= 500
               || /* Since glibc 2.10: */ _POSIX_C_SOURCE >= 200112L
               || /* glibc 2.19 and earlier */ _BSD_SOURCE

       fstatat():
           Since glibc 2.10:
               _POSIX_C_SOURCE >= 200809L
           Before glibc 2.10:
               _ATFILE_SOURCE

DESCRIPTION         top

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

       stat() and fstatat() retrieve information about the file pointed
       to by pathname; the differences for fstatat() are described
       below.

       lstat() is identical to stat(), except that if pathname is a
       symbolic link, then it returns information about the link itself,
       not the file that the link refers to.

       fstat() is identical to stat(), except that the file about which
       information is to be retrieved is specified by the file
       descriptor fd.

   The stat structure
       All of these system calls return a stat structure (see
       stat(3type)).

       Note: for performance and simplicity reasons, different fields in
       the stat structure may contain state information from different
       moments during the execution of the system call.  For example, if
       st_mode or st_uid is changed by another process by calling
       chmod(2) or chown(2), stat() might return the old st_mode
       together with the new st_uid, or the old st_uid together with the
       new st_mode.

   fstatat()
       The fstatat() system call is a more general interface for
       accessing file information which can still provide exactly the
       behavior of each of stat(), lstat(), and fstat().

       If the pathname given in pathname is relative, then it is
       interpreted relative to the directory referred to by the file
       descriptor dirfd (rather than relative to the current working
       directory of the calling process, as is done by stat() and
       lstat() for a relative pathname).

       If pathname is relative and dirfd is the special value AT_FDCWD,
       then pathname is interpreted relative to the current working
       directory of the calling process (like stat() and lstat()).

       If pathname is absolute, then dirfd is ignored.

       flags can either be 0, or include one or more of the following
       flags ORed:

       AT_EMPTY_PATH (since Linux 2.6.39)
              If pathname is an empty string, operate on the file
              referred to by dirfd (which may have been obtained using
              the open(2) O_PATH flag).  In this case, dirfd can refer
              to any type of file, not just a directory, and the
              behavior of fstatat() is similar to that of fstat().  If
              dirfd is AT_FDCWD, the call operates on the current
              working directory.  This flag is Linux-specific; define
              _GNU_SOURCE to obtain its definition.

       AT_NO_AUTOMOUNT (since Linux 2.6.38)
              Don't automount the terminal ("basename") component of
              pathname.  Since Linux 3.1 this flag is ignored.  Since
              Linux 4.11 this flag is implied.

       AT_SYMLINK_NOFOLLOW
              If pathname is a symbolic link, do not dereference it:
              instead return information about the link itself, like
              lstat().  (By default, fstatat() dereferences symbolic
              links, like stat().)

       See openat(2) for an explanation of the need for fstatat().

RETURN VALUE         top

       On success, zero is returned.  On error, -1 is returned, and
       errno is set to indicate the error.

ERRORS         top

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

       EBADF  fd is not a valid open file descriptor.

       EBADF  (fstatat()) pathname is relative but dirfd is neither
              AT_FDCWD nor a valid file descriptor.

       EFAULT Bad address.

       EINVAL (fstatat()) Invalid flag specified in flags.

       ELOOP  Too many symbolic links encountered while traversing the
              path.

       ENAMETOOLONG
              pathname is too long.

       ENOENT A component of pathname does not exist or is a dangling
              symbolic link.

       ENOENT pathname is an empty string and AT_EMPTY_PATH was not
              specified in flags.

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

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

       ENOTDIR
              (fstatat()) pathname is relative and dirfd is a file
              descriptor referring to a file other than a directory.

       EOVERFLOW
              pathname or fd refers to a file whose size, inode number,
              or number of blocks cannot be represented in,
              respectively, the types off_t, ino_t, or blkcnt_t.  This
              error can occur when, for example, an application compiled
              on a 32-bit platform without -D_FILE_OFFSET_BITS=64 calls
              stat() on a file whose size exceeds (1<<31)-1 bytes.

STANDARDS         top

       POSIX.1-2008.

HISTORY         top

       stat()
       fstat()
       lstat()
              SVr4, 4.3BSD, POSIX.1-2001.

       fstatat()
              POSIX.1-2008.  Linux 2.6.16, glibc 2.4.

       According to POSIX.1-2001, lstat() on a symbolic link need return
       valid information only in the st_size field and the file type of
       the st_mode field of the stat structure.  POSIX.1-2008 tightens
       the specification, requiring lstat() to return valid information
       in all fields except the mode bits in st_mode.

       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.)

   C library/kernel differences
       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()
       (slot __NR_stat64) on 32-bit platforms such as i386.  The first
       two versions were already present in Linux 1.0 (albeit with
       different names); the last was added in Linux 2.4.  Similar
       remarks apply for fstat() and lstat().

       The kernel-internal versions of the stat structure dealt with by
       the different versions are, respectively:

       __old_kernel_stat
              The original structure, with rather narrow fields, and no
              padding.

       stat   Larger st_ino field and padding added to various parts of
              the structure to allow for future expansion.

       stat64 Even larger st_ino field, larger st_uid and st_gid fields
              to accommodate the Linux-2.4 expansion of UIDs and GIDs to
              32 bits, and various other enlarged fields and further
              padding in the structure.  (Various padding bytes were
              eventually consumed in Linux 2.6, with the advent of
              32-bit device IDs and nanosecond components for the
              timestamp fields.)

       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.

       On modern 64-bit systems, life is simpler: there is a single
       stat() system call and the kernel deals with a stat structure
       that contains fields of a sufficient size.

       The underlying system call employed by the glibc fstatat()
       wrapper function is actually called fstatat64() or, on some
       architectures, newfstatat().

EXAMPLES         top

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

       #include <stdint.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <sys/stat.h>
       #include <sys/sysmacros.h>
       #include <time.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 (lstat(argv[1], &sb) == -1) {
               perror("lstat");
               exit(EXIT_FAILURE);
           }

           printf("ID of containing device:  [%x,%x]\n",
                  major(sb.st_dev),
                  minor(sb.st_dev));

           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:            %ju\n", (uintmax_t) sb.st_ino);

           printf("Mode:                     %jo (octal)\n",
                  (uintmax_t) sb.st_mode);

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

           printf("Preferred I/O block size: %jd bytes\n",
                  (intmax_t) sb.st_blksize);
           printf("File size:                %jd bytes\n",
                  (intmax_t) sb.st_size);
           printf("Blocks allocated:         %jd\n",
                  (intmax_t) 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         top

       ls(1), stat(1), access(2), chmod(2), chown(2), readlink(2),
       statx(2), utime(2), stat(3type), capabilities(7), inode(7),
       symlink(7)

Linux man-pages (unreleased)     (date)                          stat(2)

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