STAT(2) BSD 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 re-
quired, 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 sym-
bolic link, in which case lstat() returns information about the link,
while stat() returns information about the file the link references. Un-
like other filesystem 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() 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 concern-
ing the file.
struct stat {
dev_t st_dev; /* device inode resides on */
ino_t st_ino; /* inode's number */
mode_t st_mode; /* inode protection mode */
nlink_t st_nlink; /* number or 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 special file inode */
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 */
quad_t st_blocks; /* blocks allocated for file */
u_long st_blksize;/* optimal file sys I/O ops blocksize */
u_long st_flags; /* user defined flags for file */
u_long st_gen; /* file generation number */
};
The time-related fields of struct stat are as follows:
st_atime Time when file data last accessed. Changed by the mknod(2),
utimes(2) and read(2) system calls.
st_mtime Time when file data last modified. Changed by the mknod(2),
utimes(2) and write(2) system calls.
st_ctime Time when file status was last changed (inode data modifica-
tion). Changed by the 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_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 */
See chmod(2) for additional information on file permission masks.
The following macros are available for testing the file type masks:
S_ISBLK(st_mode) /* is a block special */
S_ISCHR(st_mode) /* is a char special */
S_ISDIR(st_mode) /* is a directory */
S_ISFIFO(st_mode) /* is a fifo or socket */
S_ISLNK(st_mode) /* is a symbolic link */
S_ISREG(st_mode) /* is a regular file */
S_ISSOCK(st_mode) /* is a fifo or socket */
S_ISWHT(st_mode) /* is a whiteout */
See dirent(5) for additional information on determining file types.
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.
COMPATIBILITY
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.
ERRORSStat() and lstat() will fail if:
[ENOTDIR] A component of the path prefix is not a directory.
[EINVAL] The pathname contains a character with the high-order bit
set.
[ENAMETOOLONG] A component of a pathname exceeded 255 characters, or an
entire path name exceeded 1023 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 ALSOaccess(2), chmod(2), chown(2), utimes(2), dir(5), symlink(7)BUGS
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 inode number.
STANDARDS
The stat() and fstat() function calls are expected to conform to IEEE Std
1003.1-1988 (``POSIX'').
HISTORY
A lstat function call appeared in 4.2BSD.
4th Berkeley Distribution May 1, 1995 3
