STAT(2)

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

LIBRARY
libc

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);
int
fstatat(int fd, const char *path, struct stat *buf, 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.

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() 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 in the case where the path specifies a relative path. In this case 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 the following list, defined in <fcntl.h>:

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

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.

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 {
        ino_t     st_ino;               /* inode's number */
        nlink_t   st_nlink;             /* number of hard links */
        dev_t     st_dev;               /* inode's device */
        mode_t    st_mode;              /* inode protection mode */
        uint16_t  st_padding1;
        uid_t     st_uid;               /* user ID of the file's owner */
        gid_t     st_gid;               /* group ID of the file's group */
        dev_t     st_rdev;              /* device type */
        struct timespec st_atim;        /* time of last access */
        struct timespec st_mtim;        /* time of last data modification */
        struct timespec st_ctim;        /* time of last file status change */
        off_t     st_size;              /* file size, in bytes */
        blkcnt_t  st_blocks;            /* blocks allocated for file */
        u_int32_t __old_st_blksize;     /* (for old ABI compat only, do not use) */
        u_int32_t st_flags;             /* user defined flags for file */
        u_int32_t st_gen;               /* file generation number */
        int32_t   st_lspare;
        blksize_t st_blksize;	    /* optimal blocksize for I/O */
        int64_t   st_qspare2;           /* (placeholder for future, do not use) */
    };

The time-related fields of struct stat are as follows:

st_atim
    Time when file data last accessed. Changed by the execve(2), mknod(2), mmap(2), read(2) and utimes(2) system calls.

st_mtim
    Time when file data last modified. Changed by the mknod(2), utimes(2) and write(2) system calls.

st_ctim
    Time when file status was last changed (inode data modification). Changed by the chmod(2), chown(2), link(2), mknod(2), rename(2), unlink(2), utimes(2) and write(2) system calls.

For compatibility with earlier versions of the POSIX standard, the following macros are defined:

    #define st_atime st_atim.tv_sec
    #define st_mtime st_mtim.tv_sec
    #define st_ctime st_ctim.tv_sec

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 */

For a list of access modes, see <sys/stat.h>, access(2) and chmod(2).

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
Stat() and lstat() will fail if:

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

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

[EFAULT]
    sb or name points to an invalid address.

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 ALSO
access(2), chmod(2), chown(2), statfs(2), statvfs(2), utimes(2), symlink(7)

STANDARDS
The stat() and fstat() system calls are expected to conform to p1003.1-90.

HISTORY
A stat() and a fstat() system call appeared in AT&T UNIX. A lstat() system call appeared in 4.2BSD. The fstatat() system call appeared in DragonFly 2.3.

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