STAT(2)

NAME
stat, lstat, fstat, fstatat - get file status

LIBRARY
libc

SYNOPSIS
#include <sys/stat.h>
int
stat(const char * restrict path, struct stat * restrict sb);
int
lstat(const char * restrict path, struct stat * restrict sb);
int
fstat(int fd, struct stat *sb);
int
fstatat(int fd, const char *path, struct stat *sb, int flag);

DESCRIPTION
The stat() system call 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() system call is like stat() except when 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 known by the file descriptor fd.

The fstatat() system call is equivalent to stat() and lstat() except when the path specifies a relative path. For fstatat() and relative path, the status is retrieved from a file relative to the directory associated with the file descriptor fd instead of the current working directory.

The values for the flag are constructed by a bitwise-inclusive OR of flags from this list, defined in <fcntl.h>:

AT_SYMLINK_NOFOLLOW
    If path names a symbolic link, the status of the symbolic link is returned.

AT_RESOLVE_BENEATH
    Only walk paths below the starting directory. See the description of the O_RESOLVE_BENEATH flag in the open(2) manual page.

AT_EMPTY_PATH
    If the path argument is an empty string, operate on the file or directory referenced by the descriptor fd. If fd is equal to AT_FDCWD, operate on the current working directory.

If fstatat() is passed the special value AT_FDCWD in the fd parameter, the current working directory is used and the behavior is identical to a call to stat() or lstat() respectively, depending on whether or not the AT_SYMLINK_NOFOLLOW bit is set in flag.

When fstatat() is called with an absolute path, it ignores the fd argument.

The sb argument is a pointer to a stat structure as defined by <sys/stat.h> and into which information is placed concerning the file.

The fields of struct stat related to the file system are:

st_dev
    Numeric ID of the device containing the file.

st_ino
    The file's inode number.

st_nlink
    Number of hard links to the file.

st_flags
    Flags enabled for the file. See chflags(2) for the list of flags and their description.

The st_dev and st_ino fields together identify the file uniquely within the system.

The time-related fields of struct stat are:

st_atim
    Time when file data was last accessed. Changed implicitly by syscalls such as read(2) and readv(2), and explicitly by utimes(2).

st_mtim
    Time when file data was last modified. Changed implicitly by syscalls such as truncate(2), write(2), and writev(2), and explicitly by utimes(2). Also, any syscall which modifies directory content changes the st_mtim for the affected directory. For instance, creat(2), mkdir(2), rename(2), link(2), and unlink(2).

st_ctim
    Time when file status was last changed (inode data modification). Changed implicitly by any syscall that affects file metadata, including st_mtim, such as chflags(2), chmod(2), chown(2), truncate(2), utimes(2), and write(2). Also, any syscall which modifies directory content changes the st_ctim for the affected directory. For instance, creat(2), mkdir(2), rename(2), link(2), and unlink(2).

st_birthtim
    Time when the inode was created.

These time-related macros are defined for compatibility:

    #define	st_atime		st_atim.tv_sec
    #define	st_mtime		st_mtim.tv_sec
    #define	st_ctime		st_ctim.tv_sec
    #ifndef _POSIX_SOURCE
    #define	st_birthtime		st_birthtim.tv_sec
    #endif
    #ifndef _POSIX_SOURCE
    #define	st_atimespec		st_atim
    #define	st_mtimespec		st_mtim
    #define	st_ctimespec		st_ctim
    #define	st_birthtimespec	st_birthtim
    #endif

Size-related fields of the struct stat are:

st_size
    File size in bytes.

st_blksize
    Optimal I/O block size for the file.

st_blocks
    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 access-related fields of struct stat are:

st_uid
    User ID of the file's owner.

st_gid
    Group ID of the file.

st_mode
    Status of the file (see below).

The status information word st_mode has these 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_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_IRWXU  0000700  /* RWX mask for owner */
    #define S_IRUSR  0000400  /* read permission, owner */
    #define S_IWUSR  0000200  /* write permission, owner */
    #define S_IXUSR  0000100  /* execute/search permission, owner */
    #define S_IRWXG  0000070  /* RWX mask for group */
    #define S_IRGRP  0000040  /* read permission, group */
    #define S_IWGRP  0000020  /* write permission, group */
    #define S_IXGRP  0000010  /* execute/search permission, group */
    #define S_IRWXO  0000007  /* RWX mask for other */
    #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). These macros are available to test whether a st_mode value passed in the m argument corresponds to a file of the specified type:

S_ISBLK(m)
    Test for a block special file.

S_ISCHR(m)
    Test for a character special file.

S_ISDIR(m)
    Test for a directory.

S_ISFIFO(m)
    Test for a pipe or FIFO special file.

S_ISLNK(m)
    Test for a symbolic link.

S_ISREG(m)
    Test for a regular file.

S_ISSOCK(m)
    Test for a socket.

S_ISWHT(m)
    Test for a whiteout.

The macros evaluate to a non-zero value if the test is true or to the value 0 if the test is false.

RETURN VALUES

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.

ERRORS
The stat() and lstat() system calls will fail if:

[EACCES]
    Search permission is denied for a component of the path prefix.

[EFAULT]
    The sb or path argument points to an invalid address.

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

[EINTEGRITY]
    Corrupted data was detected while reading from the file system.

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

[ENAMETOOLONG]
    A component of a pathname exceeded 255 characters, or an entire path name exceeded 1023 characters.

[ENOENT]
    The named file does not exist.

[ENOTDIR]
    A component of the path prefix is not a directory.

[EOVERFLOW]
    The file size in bytes cannot be represented correctly in the structure pointed to by sb.

The fstat() system call will fail if:

[EBADF]
    The fd argument is not a valid open file descriptor.

[EFAULT]
    The sb argument points to an invalid address.

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

[EINTEGRITY]
    Corrupted data was detected while reading from the file system.

[EOVERFLOW]
    The file size in bytes cannot be represented correctly in the structure pointed to by sb.

In addition to the errors returned by the lstat(), the fstatat() may fail if:

[EBADF]
    The path argument does not specify an absolute path and the fd argument is neither AT_FDCWD nor a valid file descriptor open for searching.

[EINVAL]
    The value of the flag argument is not valid.

[ENOTDIR]
    The path argument is not an absolute path and fd is neither AT_FDCWD nor a file descriptor associated with a directory.

[ENOTCAPABLE]
    path is an absolute path, or contained a ".." component leading to a directory outside of the directory hierarchy specified by fd, and the process is in capability mode or the AT_RESOLVE_BENEATH flag was specified.

SEE ALSO
access(2), chmod(2), chown(2), fhstat(2), statfs(2), utimes(2), sticky(7), symlink(7)

STANDARDS
The stat() and fstat() system calls are expected to conform to p1003.1-90. The fstatat() system call follows The Open Group Extended API Set 2 specification.

HISTORY
The stat() and fstat() system calls appeared in AT&T UNIX. The lstat() system call appeared in 4.2BSD. The fstatat() system call appeared in FreeBSD 8.0.

BUGS
Applying fstat() to a socket returns a zeroed buffer, except for the blocksize field, and a unique device and inode number.