STAT(2)

NAME
stat, fstat, lstat, fstatat - get file status

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

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

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

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

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

lstat():
    _BSD_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
    || /* Since glibc 2.10: */ _POSIX_C_SOURCE >= 200112L

fstatat():
    Since glibc 2.10:
        _XOPEN_SOURCE >= 700 || _POSIX_C_SOURCE >= 200809L
    Before glibc 2.10:
        _ATFILE_SOURCE

DESCRIPTION

These functions return information about a file, in the buffer pointed to by stat. 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 it refers to. fstat() is identical to stat(), except that the file about which informat is to be retrieved 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 filesystem I/O */
    blkcnt_t  st_blocks;      /* number of 512B blocks allocated */
    /* Since Linux 2.6, the kernel supports nanosecond
       precision for the following timestamp fields.
       For the details before Linux 2.6, see NOTES. */
    struct timespec st_atim;  /* time of last access */
    struct timespec st_mtim;  /* time of last modification */
    struct timespec st_ctim;  /* time of last status change */
#define st_atime st_atim.tv_sec      /* Backward compatibility */
#define st_mtime st_mtim.tv_sec
#define st_ctime st_ctim.tv_sec
};
Note: the order of fields in the stat structure varies somewhat across architectures. In addition, the definition above does not show the padding bytes that may be present between some fields on various architectures. Consult the the glibc and kernel source code if you need to know the details. 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 symbolic link is the length of the pathname it contains, without a terminating 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 filesystem 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 filesystem 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-user-ID 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 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 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.

  fstatat()
The fstatat() system call operates in exactly the same way as stat(), except for the differences described here. 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() 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()). 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. 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 if it is a directory that is an automount point. This allows the caller to gather attributes of an automount point (rather than the location it would mount). This flag can be used in tools that scan directories to prevent mass-automounting of a directory of automount points. The AT_NO_AUTOMOUNT flag has no effect if the mount point has already been mounted over. This flag is Linux-specific; define _GNU_SOURCE to obtain its definition.

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
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 pathname. (See also path_resolution(7).)

EBADF
    fd is bad.

EFAULT
    Bad address.

ELOOP
    Too many symbolic links encountered while traversing the path.

ENAMETOOLONG
    pathname is too long.

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

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

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

The following additional errors can occur for fstatat():

EBADF
    dirfd is not a valid file descriptor.

EINVAL
    Invalid flag specified in flags.

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

VERSIONS
fstatat() was added to Linux in kernel 2.6.16; library support was added to glibc in version 2.4.

CONFORMING TO
stat(), fstat(), lstat(): SVr4, 4.3BSD, POSIX.1-2001, POSIX.1.2008. fstatat(): POSIX.1-2008. According to POSIX.1-2001, lstat() on a symbolic link need return valid information only in the st_size field and the file-type component of the st_mode field of the stat structure. POSIX.-2008 tightens the specification, requiring lstat() to return valid information in all fields except the permission 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.) If you need to obtain the definition of the blkcnt_t or blksize_t types from <sys/stat.h>, then define _XOPEN_SOURCE with the value 500 or greater (before including any header files).

POSIX.1-1990 did not describe the S_IFMT, S_IFSOCK, S_IFLNK, S_IFREG, S_IFBLK, S_IFDIR, S_IFCHR, S_IFIFO, S_ISVTX constants, but instead demanded the use of the macros S_ISDIR(), and so on. The S_IF* constants are present in POSIX.1-2001 and later. 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 user space)
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 nondirectories: 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
On Linux, lstat() will generally not trigger automounter action, whereas stat() will (but see fstatat(2)). 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.

  Timestamp fields
Older kernels and older standards did not support nanosecond timestamp fields. Instead, there were three timestamp fields—st_atime, st_mtime, and st_ctime—typed as time_t that recorded timestamps with one-second precision. Since kernel 2.5.48, the stat structure supports nanosecond resolution for the three file timestamp fields. The nanosecond components of each timestamp are available via names of the form st_atim.tv_nsec if the _BSD_SOURCE or _SVID_SOURCE feature test macro is defined. Nanosecond timestamps are nowadays standardized, starting with POSIX.1-2008, and, starting with version 2.12, glibc also exposes the nanosecond component names if _POSIX_C_SOURCE is defined with the value 200809L or greater, or _XOPEN_SOURCE is defined with the value 700 or greater. If none of the aforementioned macros are defined, then the nanosecond values are exposed with names of the form st_atimensec. Nanosecond timestamps are supported on XFS, JFS, Btrfs, and ext4 (since Linux 2.6.23). Nanosecond timestamps are not supported in ext2, ext3, and Resierfs. On filesystems that do not support subsecond timestamps, the nanosecond fields are 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(). The underlying system call employed by the glibc fstatat() wrapper function is actually called fstatat64().

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_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));
    exit(EXIT_SUCCESS);
}

SEE ALSO
ls(1), stat(1), access(2), chmod(2), chown(2), readlink(2), utime(2), capabilities(7), symlink(7)

COLOPHON
This page is part of release 3.63 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.