STAT(2)

NAME
stat, fstat, lstat - get file status

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

int stat(const char *file_name, struct stat *buf);
int fstat(int filedes, struct stat *buf);
int lstat(const char *file_name, struct stat *buf);

DESCRIPTION

These functions return information about the specified file. You do not need any access rights to the file to get this information but you need search rights to all directories named in the path leading to the file.

stat stats the file pointed to by file_name and fills in buf. lstat is identical to stat, only the link itself is stated, not the file that is obtained by tracing the links. fstat is identical to stat, only the open file pointed to by filedes (as returned by open(2)) is stated in place of file_name.

They all return a stat structure, which is declared as follows:

    struct stat
    {
        dev_t         st_dev;      /* device */
        ino_t         st_ino;      /* inode */
        umode_t       st_mode;     /* protection */
        nlink_t       st_nlink;    /* number of hard links */
        uid_t         st_uid;      /* user ID of owner */
        gid_t         st_gid;      /* group ID of owner */
        dev_t         st_rdev;     /* device type (if inode device) */
        off_t         st_size;     /* total size, in bytes */
        unsigned long st_blksize;  /* blocksize for filesystem I/O */
        unsigned long st_blocks;   /* number of blocks allocated */
        time_t        st_atime;    /* time of last access */
        time_t        st_mtime;    /* time of last modification */
        time_t        st_ctime;    /* time of last change */
    };

Note that st_blocks may not always be in terms of blocks of size st_blksize, and that st_blksize may instead provide a notion of the "preferred" blocksize for efficient file system I/O.

Not all of the Linux filesystems implement all of the time fields. Traditionally, st_atime is changed by mknod(2), utime(2), read(2), write(2), and truncate(2). Traditionally, st_mtime is changed by mknod(2), utime(2), and write(2). The st_mtime is not changed for changes in owner, group, hard link count, or mode. Traditionally, st_ctime is changed by writing or by setting inode information (i.e., owner, group, link count, mode, etc.).

The following macros are defined to check the file type:

    S_ISLNK(m)
        is it a symbolic link?

    S_ISREG(m)
        regular file?

    S_ISDIR(m)
        directory?

    S_ISCHR(m)
        character device?

    S_ISBLK(m)
        block device?

    S_ISFIFO(m)
        fifo?

    S_ISSOCK(m)
        socket?

The following flags are defined for the st_mode field:

    S_IFMT
        00170000 bitmask for the file type bitfields

    S_IFSOCK
        0140000 socket

    S_IFLNK
        0120000 symbolic link

    S_IFREG
        0100000 regular file

    S_IFBLK
        0060000 block device

    S_IFDIR
        0040000 directory

    S_IFCHR
        0020000 character device

    S_IFIFO
        0010000 fifo

    S_ISUID
        0004000 set UID bit

    S_ISGID
        0002000 set GID bit

    S_ISVTX
        0001000 sticky bit

    S_IRWXU
        00700 user (file owner) has read, write and execute permission

    S_IRUSR (S_IREAD)
        00400 user has read permission

    S_IWUSR (S_IWRITE)
        00200 user has write permission

    S_IXUSR (S_IEXEC)
        00100 user has execute permission

    S_IRWXG
        00070 group has read, write and execute permission

    S_IRGRP
        00040 group has read permission

    S_IWGRP
        00020 group has write permission

    S_IXGRP
        00010 group has execute permission

    S_IRWXO
        00007 others have read, write and execute permission

    S_IROTH
        00004 others have read permission

    S_IWOTH
        00002 others have write permisson

    S_IXOTH
        00001 others have execute permission

RETURN VALUE
On success, zero is returned. On error, -1 is returned, and errno is set appropriately.

ERRORS

EBADF
    filedes is bad.

ENOENT
    File does not exist.

EFAULT
    Bad address.

EACCES
    Permission denied.

ENOMEM
    Out of memory (i.e. kernel memory).

ENAMETOOLONG
    File name too long.

CONFORMING TO
The stat and fstat calls conform to SVr4, SVID, POSIX, X/OPEN, BSD 4.3. The lstat call conforms to 4.3BSD and SVr4. SVr4 documents additional fstat error conditions EFAULT, EINTR, ENOLINK, and EOVERFLOW. SVr4 documents additional stat and lstat error conditions EACCES, EFAULT, EINTR, ELOOP, EMULTIHOP, ENAMETOOLONG, ENOTDIR, ENOLINK, and EOVERFLOW.

SEE ALSO
chmod(2), chown(2), readlink(2), utime(2)