stat(2)
NAME
stat, lstat, fstat − get file status
SYNTAX
#include <sys/types.h>
#include <sys/stat.h>
stat(path, buf)
char *path;
struct stat *buf;
lstat(path, buf)
char *path;
struct stat *buf;
fstat(fd, buf)
int fd;
struct stat *buf;
DESCRIPTION
The stat system call obtains information about the file 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 reachable.
The lstat system call 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 system call obtains the same information about an open file referenced by the argument descriptor, such as would be obtained by an open call.
The buf is a pointer to a stat structure into which information is placed concerning the file. The contents of the structure pointed to by buf
struct stat {
dev_t st_dev; /* device inode resides on */
ino_t st_ino; /* this inode’s number */
u_short st_mode; /* protection */
short st_nlink; /* number or hard links to the file */
short st_uid; /* user-id of owner */
short st_gid; /* group-id of owner */
dev_t st_rdev; /* the device type, for inode that is device */
off_t st_size; /* total size of file */
time_t st_atime; /* file last access time */
int st_spare1;
time_t st_mtime; /* file last modify time */
int st_spare2;
time_t st_ctime; /* file last status change time */
int st_spare3;
long st_blksize; /* optimal blocksize for file system i/o ops */
long st_blocks; /* actual number of blocks allocated */
long st_spare4[2];
};
st_atime Time when file data was last read or modified. Changed by the following system calls, mknod(,), utimes(,), and read(.). For reasons of efficiency, st_atime is not set when a directory is searched, although this would be more logical.
st_mtime Time when data was last modified. It is not set by changes of owner, group, link count, or mode. Changed by the following system calls, mknod(,), utimes(,), and write(.).
st_ctime Time when file status was last changed. It is set both both by writing and changing the i-node. Changed by the following system calls, chmod(,), chown(,), link(,), mknod(,), unlink(,), utimes(,), and write(.).
The status information word st_mode has bits:
#define S_IFMT 0170000 /* type of file */
#define S_IFDIR 0040000 /* directory */
#define S_IFCHR 0020000 /* character special */
#define S_IFBLK 0060000 /* block special */
#define S_IFREG 0100000 /* regular */
#define S_IFLNK 0120000 /* symbolic link */
#define S_IFSOCK 0140000 /* socket */
#define S_IFIFO 0010000 /* FIFO - named pipe */
#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_IREAD 0000400 /* read permission, owner */
#define S_IWRITE 0000200 /* write permission, owner */
#define S_IEXEC 0000100 /* execute/search permission, owner */
The mode bits 0000070 and 0000007 encode group and others permissions. For further information, see chmod(.).
When fd is associated with a pipe, fstat returns a buffer with only st_blksize set.
RETURN VALUE
Upon successful completion a value of 0 is returned. Otherwise, a value of −1 is returned and errno is set to indicate the error.
RESTRICTIONS
Applying fstat to a socket returns a zeroed buffer and [EOPNOTSUPP].
The fields in the stat structure currently marked st_spare1, st_spare2, and st_spare3 are present in preparation for inode time stamps expanding to 64 bits. This, however, can break certain programs which depend on the time stamps being contiguous, in calls to utimes(.).
ENVIRONMENT
Differs from the System V definition in that ELOOP is a possible error condition.
DIAGNOSTICS
The stat and lstat system calls will fail if one or more of the following are true:
[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.
[EFAULT] The buf or name points to an invalid address.
[ELOOP] Too many symbolic links were encountered in translating the pathname.
[EIO] An I/O error occurred while reading from or writing to the file system.
The fstat system call will fail if one or both of the following are true:
[EBADF] The fildes is not a valid open file descriptor.
[EFAULT] The buf points to an invalid address.
[EIO] An I/O error occurred while reading from or writing to the file system.
[EOPNOTSUPP]
The file descriptor points to a socket.
[ETIMEDOUT] A "connect" request or remote file operation failed because the connected party did not properly respond after a period of time which is dependent on the communications protocol.