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 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. Unlike 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 concerning 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 modification). 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 */

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

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.

ERRORS
Stat() and lstat() will fail if:

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

[ENAMETOOLONG]
    A component of a pathname exceeded {NAME_MAX} characters, or an entire path name exceeded {PATH_MAX} 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.

CAVEATS
The file generation number, st_gen, is only available to the super-user.
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)).

SEE ALSO
chmod(2), chown(2), utimes(2) 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 p1003.1-88.

HISTORY
An lstat() function call appeared in 4.2BSD.