NAME
stat, lstat, fstat - get file status

SYNOPSIS
#include <sys/types.h>
#include <sys/stat.h>

stat(path, buf)
const char *path;
struct stat *buf;

lstat(path, buf)
const char *path;
struct stat *buf;

fstat(fd, buf)
int fd;
struct stat *buf;

DESCRIPTION
Stat 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.

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.

Fstat obtains the same information about an open file referenced by
the argument descriptor, such as would be obtained by an open call.

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 */
uid_t st_uid; /* user-id of owner */
gid_t 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 accessed. Changed by the
following system calls: mknod(2), utimes(2), and
read(2). 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(2), utimes(2),
write(2).

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(2) chown(2), link(2),
mknod(2), rename(2), unlink(2), utimes(2), write(2).

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_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 (see chmod(2)).

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.

ERRORS
Stat and lstat 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.

[ELOOP] Too many symbolic links were encountered in
translating the pathname.

[EFAULT] Buf 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 one or both of the following are true:

[EBADF] Fildes is not a valid open file descriptor.

[EFAULT] Buf points to an invalid address.

[EIO] An I/O error occurred while reading from or writing
to the file system.

CAVEAT
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 that depend on the time stamps being contiguous (in calls
to utimes(2)).