STAT(2) OpenBSD Programmer's Manual STAT(2)NAME
stat, lstat, fstat - get file status
SYNOPSIS
#include <sys/types.h>
#include <sys/stat.h>
int
stat(const char *path, struct stat *sb);
int
lstat(const char *path, struct stat *sb);
int
fstat(int fd, struct stat *sb);
DESCRIPTION
The stat() function obtains information about the file pointed to by
path. Read, write, or execute permission of the named file is not
required, but all directories listed in the path name leading to the file
must be searchable.
The lstat() function is identical to stat() except when the named file is
a symbolic link, in which case lstat() returns information about the link
itself, not the file the link references. Unlike other file system
objects, symbolic links do not have an owner, group, access mode, times,
etc. Instead, these attributes are taken from the directory that
contains the link. The only attributes returned from an lstat() that
refer to the symbolic link itself are the file type (S_IFLNK), size,
blocks, and link count (always 1).
The fstat() function obtains the same information about an open file
known by the file descriptor fd.
The sb argument is a pointer to a stat() structure as defined by
<sys/stat.h> (shown below) and into which information is placed
concerning the file.
struct stat {
dev_t st_dev; /* inode's device */
ino_t st_ino; /* inode's number */
mode_t st_mode; /* inode protection mode */
nlink_t st_nlink; /* number of hard links */
uid_t st_uid; /* user ID of the file's owner */
gid_t st_gid; /* group ID of the file's group */
dev_t st_rdev; /* device type */
struct timespec st_atim; /* time of last access */
struct timespec st_mtim; /* time of last data modification */
struct timespec st_ctim; /* time of last file status change */
off_t st_size; /* file size, in bytes */
int64_t st_blocks; /* blocks allocated for file */
u_int32_t st_blksize;/* optimal blocksize for I/O */
u_int32_t st_flags; /* user defined flags for file */
u_int32_t st_gen; /* file generation number */
};
The time-related fields of struct stat are represented in struct timespec
format, which has nanosecond precision. However, the actual precision is
generally limited by the file system holding the file. The fields are as
follows:
st_atim Time when file data was last accessed. Set when the file
system object was created and updated by the utimes(2) and
read(2) system calls.
st_mtim Time when file data was last modified. Changed by the
truncate(2), utimes(2), and write(2) system calls. For
directories, changed by any system call that alters which
files are in the directory, such as the unlink(2), rename(2),
mkdir(2), and symlink(2) system calls.
st_ctim Time when file status was last changed (inode data
modification). Changed by the chmod(2), chown(2), link(2),
rename(2), unlink(2), utimes(2), and write(2) system calls.
In addition, all the time fields are set to the current time when a file
system object is first created by the mkdir(2), mkfifo(2), mknod(2),
open(2), and symlink(2) system calls.
For compatibility with previous standards, st_atime, st_mtime, and
st_ctime macros are provided that expand to the tv_secs member of their
respective struct timespec member. Deprecated macros are also provided
for some transitional names: st_atimensec, st_mtimensec, st_ctimensec,
st_atimespec, st_mtimespec, and st_ctimespec
The size-related fields of the struct stat are as follows:
st_blksize The optimal I/O block size for the file.
st_blocks The actual number of blocks allocated for the file in 512-
byte units. As short symbolic links are stored in the
inode, this number may be zero.
The status information word st_mode has the following bits:
#define S_IFMT 0170000 /* type of file mask */
#define S_IFIFO 0010000 /* named pipe (fifo) */
#define S_IFCHR 0020000 /* character special */
#define S_IFDIR 0040000 /* directory */
#define S_IFBLK 0060000 /* block special */
#define S_IFREG 0100000 /* regular */
#define S_IFLNK 0120000 /* symbolic link */
#define S_IFSOCK 0140000 /* socket */
#define S_ISUID 0004000 /* set-user-ID on execution */
#define S_ISGID 0002000 /* set-group-ID on execution */
#define S_ISVTX 0001000 /* save swapped text even after use */
#define S_IRWXU 0000700 /* RWX mask for owner */
#define S_IRUSR 0000400 /* R for owner */
#define S_IWUSR 0000200 /* W for owner */
#define S_IXUSR 0000100 /* X for owner */
#define S_IRWXG 0000070 /* RWX mask for group */
#define S_IRGRP 0000040 /* R for group */
#define S_IWGRP 0000020 /* W for group */
#define S_IXGRP 0000010 /* X for group */
#define S_IRWXO 0000007 /* RWX mask for other */
#define S_IROTH 0000004 /* R for other */
#define S_IWOTH 0000002 /* W for other */
#define S_IXOTH 0000001 /* X for other */
The following macros test a file's type. If the file is of that type, a
non-zero value is returned; otherwise, 0 is returned.
S_ISBLK(st_mode m) /* block special */
S_ISCHR(st_mode m) /* char special */
S_ISDIR(st_mode m) /* directory */
S_ISFIFO(st_mode m) /* fifo */
S_ISLNK(st_mode m) /* symbolic link */
S_ISREG(st_mode m) /* regular file */
S_ISSOCK(st_mode m) /* socket */
For a list of access modes, see <sys/stat.h>, access(2), and chmod(2).
RETURN VALUES
Upon successful completion a value of 0 is returned. Otherwise, a value
of -1 is returned and errno is set to indicate the error.
ERRORSstat() and lstat() will fail if:
[ENOTDIR] A component of the path prefix is not a directory.
[ENAMETOOLONG]
A component of a pathname exceeded NAME_MAX characters, or
an entire path name exceeded PATH_MAX characters.
[ENOENT] The named file does not exist.
[EACCES] Search permission is denied for a component of the path
prefix.
[ELOOP] Too many symbolic links were encountered in translating the
pathname.
[EFAULT] sb or name points to an invalid address.
[EIO] An I/O error occurred while reading from or writing to the
file system.
fstat() will fail if:
[EBADF] fd is not a valid open file descriptor.
[EFAULT] sb points to an invalid address.
[EIO] An I/O error occurred while reading from or writing to the
file system.
SEE ALSOchmod(2), chown(2), utimes(2), symlink(7)STANDARDS
Previous versions of the system used different types for the st_dev,
st_uid, st_gid, st_rdev, st_size, st_blksize, and st_blocks fields.
The stat() and fstat() function calls are expected to conform to IEEE Std
1003.1-1988 (``POSIX'').
HISTORY
A stat() function appeared in Version 2 AT&T UNIX. An lstat() function
call appeared in 4.2BSD.
CAVEATS
The file generation number, st_gen, is only available to the superuser.
Certain programs written when the timestamps were just of type time_t
assumed that the members were consecutive (and could therefore be placed
directly to utimes(2)). The transition to timestamps of type struct
timespec broke them irrevocably.
BUGS
Applying fstat() to a socket (and thus to a pipe) returns a zeroed
buffer, except for the blocksize field, and a unique device and inode
number.
OpenBSD 4.9 November 10, 2009 OpenBSD 4.9
