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STAT(2) | Linux Programmer's Manual | STAT(2) |
NAME¶
stat, fstat, lstat, fstatat - get file statusSYNOPSIS¶
#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 ||
_XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
|| /* Since glibc 2.10: */ _POSIX_C_SOURCE >= 200112L
- 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.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 };
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 |
Thus, to test for a regular file (for example), one could write:
Because tests of the above form are common, additional macros are defined by POSIX to allow the test of the file type in st_mode to be written more concisely:
stat(pathname, &sb); if ((sb.st_mode & S_IFMT) == S_IFREG) { /* Handle regular file */ }
- 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 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_IFSOCK and S_ISSOCK() are provided if _XOPEN_SOURCE is defined. The definition of S_IFSOCK can also be exposed by defining _XOPEN_SOURCE with a value of 500 or greater.
stat(pathname, &sb); if (S_ISREG(sb.st_mode)) { /* Handle regular file */ }
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.- 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). If dirfd is AT_FDCWD, the call operates on the current working directory. 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().)
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.
- 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.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) |
NOTES¶
On Linux, lstat() will generally not trigger automounter action, whereas stat() will (but see fstatat(2)).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.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_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 3.74 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at http://www.kernel.org/doc/man-pages/.2014-08-19 | Linux |