stat(2) — Linux manual pages

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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)`;

Note

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 filesystem I/O */

blkcnt_t st_blocks;
/* number of 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 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 filesystems implement all of the time fields. Some file system types allow mounting in such a way that file accesses do not cause an update of the st_atime field. (See "noatime" in mount(8).)

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 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.

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 the path path does not exist, or the path is an empty string.
ENOMEM: Out of memory (i.e., kernel memory).
ENOTDIR: A component of the path is not a directory.

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 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	SysV 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

Linux 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.

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 inode 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);
}

COLOPHON

This page is part of release 2.79 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/.

  t

Copyright (c) 1992 Drew Eckhardt (drewcs.colorado.edu), March 28, 1992
Parts Copyright (c) 1995 Nicolai Langfeldt (janlifi.uio.no), 1/1/95
and Copyright (c) 2007 Michael Kerrisk <mtk.manpagesgmail.com>

Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.

Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the
entire resulting derived work is distributed under the terms of a
permission notice identical to this one.

Since the Linux kernel and libraries are constantly changing, this
manual page may be incorrect or out-of-date.  The author(s) assume no
responsibility for errors or omissions, or for damages resulting from
the use of the information contained herein.  The author(s) may not
have taken the same level of care in the production of this manual,
which is licensed free of charge, as they might when working
professionally.

Formatted or processed versions of this manual, if unaccompanied by
the source, must acknowledge the copyright and authors of this work.

Modified by Michael Haardt <michaelmoria.de>
Modified 1993-07-24 by Rik Faith <faithcs.unc.edu>
Modified 1995-05-18 by Todd Larason <jtlmolehill.org>
Modified 1997-01-31 by Eric S. Raymond <esrthyrsus.com>
Modified 1995-01-09 by Richard Kettlewell <richardgreenend.org.uk>
Modified 1998-05-13 by Michael Haardt <michaelcantor.informatik.rwth-aachen.de>
Modified 1999-07-06 by aeb & Albert Cahalan
Modified 2000-01-07 by aeb
Modified 2004-06-23 by Michael Kerrisk <mtk.manpagesgmail.com>
2007-06-08 mtk: Added example program
2007-07-05 mtk: Added details on underlying system call interfaces

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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 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 */
};

`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