Manpage of STAT


Section: Linux Programmer's Manual (2)
Updated: 2016-10-08


stat, fstat, lstat, fstatat - get file status  


#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)):


/* glibc 2.19 and earlier */ _BSD_SOURCE

    || /* Since glibc 2.20 */ _DEFAULT_SOURCE

    || _XOPEN_SOURCE >= 500

    || /* Since glibc 2.10: */ _POSIX_C_SOURCE >= 200112L


Since glibc 2.10:
_POSIX_C_SOURCE >= 200809L
Before glibc 2.10:


These functions return information about a file, in the buffer pointed to by buf. 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 pathnamethat 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 pathnameis 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 information is to be retrieved is specified by the file descriptor fd.

All of these system calls return a statstructure, 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;        /* file type and mode */
    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 statstructure 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 glibc and kernel source code if you need to know the details.

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

The st_devfield 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_rdevfield describes the device that this file (inode) represents.

The st_sizefield 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_blocksfield 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_blksizefield 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_atimefield. (See noatime, nodiratime, and relatimein mount(8), and related information in mount(2).) In addition, st_atimeis not updated if a file is opened with the O_NOATIME; see open(2).

The field st_atimeis 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_mtimeis changed by file modifications, for example, by mknod(2), truncate(2), utime(2), and write(2) (of more than zero bytes). Moreover, st_mtimeof a directory is changed by the creation or deletion of files in that directory. The st_mtimefield is notchanged for changes in owner, group, hard link count, or mode.

The field st_ctimeis changed by writing or by setting inode information (i.e., owner, group, link count, mode, etc.).

POSIX refers to the st_modebits corresponding to the mask S_IFMT(see below) as the file type, the 12 bits corresponding to the mask 07777 as the file mode bitsand the least significant 9 bits (0777) as the file permission bits.

The following mask values are defined for the file type of the st_modefield:

S_IFMT0170000bit mask for the file type bit field

S_IFLNK0120000symbolic link
S_IFREG0100000regular file
S_IFBLK0060000block device
S_IFCHR0020000character device

Thus, to test for a regular file (for example), one could write:

stat(pathname, &sb);
if ((sb.st_mode & S_IFMT) == S_IFREG) {
    /* Handle regular file */

Because tests of the above form are common, additional macros are defined by POSIX to allow the test of the file type in st_modeto be written more concisely:

is it a regular file?
character device?
block device?
FIFO (named pipe)?
symbolic link? (Not in POSIX.1-1996.)
socket? (Not in POSIX.1-1996.)

The preceding code snippet could thus be rewritten as:

stat(pathname, &sb);
if (S_ISREG(sb.st_mode)) {
    /* Handle regular file */

The definitions of most of the above file type test macros are provided if any of the following feature test macros is defined: _BSD_SOURCE(in glibc 2.19 and earlier), _SVID_SOURCE(in glibc 2.19 and earlier), or _DEFAULT_SOURCE(in glibc 2.20 and later). In addition, definitions of all of the above macros except S_IFSOCKand S_ISSOCK() are provided if _XOPEN_SOURCEis defined. The definition of S_IFSOCKcan also be exposed by defining _XOPEN_SOURCEwith a value of 500 or greater.

The definition of S_ISSOCK() is exposed if any of the following feature test macros is defined: _BSD_SOURCE(in glibc 2.19 and earlier), _DEFAULT_SOURCE(in glibc 2.20 and later), _XOPEN_SOURCEwith a value of 500 or greater, or _POSIX_C_SOURCEwith a value of 200112L or greater.

The following mask values are defined for the file mode component of the st_modefield:

S_ISUID 04000set-user-ID bit
S_ISGID 02000set-group-ID bit (see below)
S_ISVTX 01000sticky bit (see below)

S_IRWXU 00700owner has read, write, and execute permission
S_IRUSR 00400owner has read permission
S_IWUSR 00200owner has write permission
S_IXUSR 00100owner has execute permission

S_IRWXG 00070group has read, write, and execute permission
S_IRGRP 00040group has read permission
S_IWGRP 00020group has write permission
S_IXGRP 00010group has execute permission

S_IRWXO 00007others (not in group) have read, write, and execute permission
S_IROTH 00004others have read permission
S_IWOTH 00002others have write permission
S_IXOTH 00001others 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_ISGIDbit 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.  


The fstatat() system call operates in exactly the same way as stat(), except for the differences described here.

If the pathname given in pathnameis 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 pathnameis relative and dirfdis the special value AT_FDCWD, then pathnameis interpreted relative to the current working directory of the calling process (like stat()).

If pathnameis absolute, then dirfdis ignored.

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

AT_EMPTY_PATH (since Linux 2.6.39)
If pathnameis an empty string, operate on the file referred to by dirfd(which may have been obtained using the open(2) O_PATHflag). If dirfdis AT_FDCWD, the call operates on the current working directory. In this case, dirfdcan refer to any type of file, not just a directory. This flag is Linux-specific; define _GNU_SOURCEto obtain its definition.
AT_NO_AUTOMOUNT (since Linux 2.6.38)
Don't automount the terminal ("basename") component of pathnameif 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_AUTOMOUNTflag has no effect if the mount point has already been mounted over. This flag is Linux-specific; define _GNU_SOURCEto obtain its definition.
If pathnameis 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().  


On success, zero is returned. On error, -1 is returned, and errnois set appropriately.  


Search permission is denied for one of the directories in the path prefix of pathname. (See also path_resolution(7).)
fdis not a valid open file descriptor.
Bad address.
Too many symbolic links encountered while traversing the path.
pathnameis too long.
A component of pathnamedoes not exist, or pathnameis an empty string.
Out of memory (i.e., kernel memory).
A component of the path prefix of pathnameis not a directory.
pathnameor fdrefers 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=64calls stat() on a file whose size exceeds (1<<31)-1bytes.

The following additional errors can occur for fstatat():

dirfdis not a valid file descriptor.
Invalid flag specified in flags.
pathnameis relative and dirfdis a file descriptor referring to a file other than a directory.


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


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_sizefield and the file type of the st_modefield of the statstructure. 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_blocksand st_blksizefields 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_tor blksize_ttypes from <sys/stat.h>, then define _XOPEN_SOURCEwith the value 500 or greater (before including anyheader 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_ISVTXconstants, 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:
f000S_IFMT170000mask for file type
0000000000SCO out-of-service inode; BSD unknown type; SVID-v2 and XPG2 have both 0 and 0100000 for ordinary file
1000S_IFIFOp|010000FIFO (named pipe)
2000S_IFCHRc020000character special (V7)
3000S_IFMPC030000multiplexed character special (V7)
4000S_IFDIRd/040000directory (V7)
5000S_IFNAM050000XENIX named special file with two subtypes, distinguished by st_rdev values 1, 2
0001S_INSEMs000001XENIX semaphore subtype of IFNAM
0002S_INSHDm000002XENIX shared data subtype of IFNAM
6000S_IFBLKb060000block special (V7)
7000S_IFMPB070000multiplexed block special (V7)
8000S_IFREG-100000regular (V7)
9000S_IFCMP110000VxFS compressed
9000S_IFNWKn110000network special (HP-UX)
a000S_IFLNKl@120000symbolic link (BSD)
b000S_IFSHAD130000Solaris shadow inode for ACL (not seen by user space)
c000S_IFSOCKs=140000socket (BSD; also "S_IFSOC" on VxFS)
d000S_IFDOORD>150000Solaris door
e000S_IFWHTw%160000BSD whiteout (not used for inode)
0200S_ISVTX001000sticky 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)
0400S_ISGID002000set-group-ID on execution (V7)
for directories: use BSD semantics for propagation of GID
0400S_ENFMT002000System V file locking enforcement (shared with S_ISGID)
0800S_ISUID004000set-user-ID on execution (V7)
0800S_CDF004000directory is a context dependent file (HP-UX)

A sticky command appeared in Version 32V AT&T UNIX.  


On Linux, lstat() will generally not trigger automounter action, whereas stat() will (but see fstatat(2)).

For pseudofiles that are autogenerated by the kernel, stat() does not return an accurate value in the st_sizefield. For example, the value 0 is returned for many files under the /procdirectory, while various files under /sysreport a size of 4096 bytes, even though the file content is smaller. For such files, one should simply try to read as many bytes as possible (and append aq\0aq to the returned buffer if it is to be interpreted as a string).  

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_tthat recorded timestamps with one-second precision.

Since kernel 2.5.48, the statstructure 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 suitable feature test macros are defined. Nanosecond timestamps were standardized in POSIX.1-2008, and, starting with version 2.12, glibc exposes the nanosecond component names if _POSIX_C_SOURCEis defined with the value 200809L or greater, or _XOPEN_SOURCEis defined with the value 700 or greater. Up to and including glibc 2.19, the definitions of the nanoseconds components are also defined if _BSD_SOURCEor _SVID_SOURCEis defined. 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 Reiserfs. On filesystems that do not support subsecond timestamps, the nanosecond fields are returned with the value 0.  

C library/kernel differences

Over time, increases in the size of the statstructure 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 statstructure dealt with by the different versions are, respectively:

The original structure, with rather narrow fields, and no padding.
Larger st_inofield and padding added to various parts of the structure to allow for future expansion.
Even larger st_inofield, larger st_uidand st_gidfields 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 statstructure 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().  


The following program calls stat() and displays selected fields in the returned statstructure.
#include <sys/types.h>
#include <sys/stat.h>
#include <time.h>
#include <stdio.h>
#include <stdlib.h>

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

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

    if (stat(argv[1], &sb) == -1) {

    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));



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



Other systems
Timestamp fields
C library/kernel differences

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