stat, lstat, fstat - get file status
Standard C Library (libc, -lc)
#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);
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.
lstat() is like stat() except in the case where the named file is a symbolic
link, in which case lstat() returns information about the link,
while stat() returns information about the file the link references.
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; /* device containing the file */
ino_t st_ino; /* file's serial number */
mode_t st_mode; /* file's mode (protection and type) */
nlink_t st_nlink; /* number of hard links to the file */
uid_t st_uid; /* user-id of owner */
gid_t st_gid; /* group-id of owner */
dev_t st_rdev; /* device type, for device special file */
struct timespec st_atimespec; /* time of last access */
struct timespec st_mtimespec; /* time of last data modification */
struct timespec st_ctimespec; /* 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 file sys I/O ops blocksize */
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 as follows:
st_atime Time when file data was last accessed. Changed by the
mknod(2), utimes(2) and read(2) system calls.
st_mtime Time when file data was last modified. Changed by the
mknod(2), utimes(2) and write(2) system calls.
st_ctime Time when file status was last changed (file metadata modification).
Changed by the chflags(2), chmod(2), chown(2),
link(2), mknod(2), rename(2), unlink(2), utimes(2) and
write(2) system calls.
The size-related fields of the struct stat are as follows:
st_size The size of the file in bytes. A directory will be a multiple
of the size of the dirent(5) structure.
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 */
#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_IFWHT 0160000 /* whiteout */
#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_IRUSR 0000400 /* read permission, owner */
#define S_IWUSR 0000200 /* write permission, owner */
#define S_IXUSR 0000100 /* execute/search permission, owner */
#define S_IRGRP 0000040 /* read permission, group */
#define S_IWGRP 0000020 /* write permission, group */
#define S_IXGRP 0000010 /* execute/search permission, group */
#define S_IROTH 0000004 /* read permission, other */
#define S_IWOTH 0000002 /* write permission, other */
#define S_IXOTH 0000001 /* execute/search permission, other */
For a list of access modes, see <sys/stat.h>, access(2) and chmod(2).
The status information word st_flags has the following bits:
#define UF_NODUMP 0x00000001 /* do not dump file */
#define UF_IMMUTABLE 0x00000002 /* file may not be changed */
#define UF_APPEND 0x00000004 /* writes to file may only append */
#define UF_OPAQUE 0x00000008 /* directory is opaque wrt. union */
#define SF_ARCHIVED 0x00010000 /* file is archived */
#define SF_IMMUTABLE 0x00020000 /* file may not be changed */
#define SF_APPEND 0x00040000 /* writes to file may only append */
For a description of the flags, see chflags(2).
Upon successful completion a value of 0 is returned. Otherwise, a value
of -1 is returned and errno is set to indicate the error.
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.
stat() 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.
[EBADF] A badly formed v-node was encountered. This can happen
if a file system information node is incorrect.
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.
chflags(2), chmod(2), chown(2), utimes(2), dir(5), symlink(7)
The stat() and fstat() functions conform to ISO/IEC 9945-1:1990
(``POSIX.1'').
A lstat() function call appeared in 4.2BSD.
Applying fstat() to a socket (and thus to a pipe) returns a zero'd
buffer, except for the blocksize field, and a unique device and file
serial number.
BSD May 1, 1995 BSD
[ Back ] |
