stat, fstat, lstat, fstatat - get file status

#include <sys/stat.h>
int stat(const char *restrict pathname,
 struct stat *restrict statbuf);
int fstat(int fd, struct stat *statbuf);
int lstat(const char *restrict pathname,
 struct stat *restrict statbuf);
#include <fcntl.h> /* Definition of AT_* constants */
#include <sys/stat.h>
int fstatat(int dirfd, const char *restrict pathname,
 struct stat *restrict statbuf, int flags);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

    /* Since glibc 2.20 */ _DEFAULT_SOURCE
        || _XOPEN_SOURCE >= 500
        || /* Since glibc 2.10: */ _POSIX_C_SOURCE >= 200112L
        || /* glibc 2.19 and earlier */ _BSD_SOURCE

    Since glibc 2.10:
        _POSIX_C_SOURCE >= 200809L
    Before glibc 2.10:
        _ATFILE_SOURCE

These functions return information about a file, in the buffer pointed to by statbuf. No permissions are required on the file itself, but—in the case of stat(), fstatat(), and lstat()—execute (search) permission is required on all of the directories in pathname that lead to the file.

stat() and fstatat() retrieve information about the file pointed to by pathname; the differences for fstatat() are described below.

lstat() is identical to stat(), except that if pathname is a symbolic link, then it returns information about the link itself, not the file that the link refers to.

fstat() is identical to stat(), except that the file about which information is to be retrieved is specified by the file descriptor fd.

The stat structure

All of these system calls return a stat structure (see stat(3type)).

Note: for performance and simplicity reasons, different fields in the stat structure may contain state information from different moments during the execution of the system call. For example, if st_mode or st_uid is changed by another process by calling chmod(2) or chown(2), stat() might return the old st_mode together with the new st_uid, or the old st_uid together with the new st_mode.

fstatat()

The fstatat() system call is a more general interface for accessing file information which can still provide exactly the behavior of each of stat(), lstat(), and fstat().

If the pathname given in pathname is relative, then it is interpreted relative to the directory referred to by the file descriptor dirfd (rather than relative to the current working directory of the calling process, as is done by stat() and lstat() for a relative pathname).

If pathname is relative and dirfd is the special value AT_FDCWD, then pathname is interpreted relative to the current working directory of the calling process (like stat() and lstat()).

If pathname is absolute, then dirfd is ignored.

flags can either be 0, or include one or more of the following flags ORed:

AT_EMPTY_PATH (since Linux 2.6.39)

If pathname is an empty string, operate on the file referred to by dirfd (which may have been obtained using the open(2) O_PATH flag). In this case, dirfd can refer to any type of file, not just a directory, and the behavior of fstatat() is similar to that of fstat(). If dirfd is AT_FDCWD, the call operates on the current working directory. This flag is Linux-specific; define _GNU_SOURCE to obtain its definition.

AT_NO_AUTOMOUNT (since Linux 2.6.38)

Don't automount the terminal ("basename") component of pathname. Since Linux 3.1 this flag is ignored. Since Linux 4.11 this flag is implied.

AT_SYMLINK_NOFOLLOW

If pathname is a symbolic link, do not dereference it: instead return information about the link itself, like lstat(). (By default, fstatat() dereferences symbolic links, like stat().)

See openat(2) for an explanation of the need for fstatat().

On success, zero is returned. On error, -1 is returned, and errno is set to indicate the error.

The following program calls lstat() and displays selected fields in the returned stat structure.

#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <sys/sysmacros.h>
#include <time.h>
int
main(int argc, char *argv[])
{
    struct stat sb;
    if (argc != 2) {
        fprintf(stderr, "Usage: %s <pathname>\n", argv[0]);
        exit(EXIT_FAILURE);
    }
    if (lstat(argv[1], &sb) == -1) {
        perror("lstat");
        exit(EXIT_FAILURE);
    }
    printf("ID of containing device:  [%x,%x]\n",
           major(sb.st_dev),
           minor(sb.st_dev));
    printf("File type:                ");
    switch (sb.st_mode & S_IFMT) {
    case S_IFBLK:  printf("block device\n");            break;
    case S_IFCHR:  printf("character device\n");        break;
    case S_IFDIR:  printf("directory\n");               break;
    case S_IFIFO:  printf("FIFO/pipe\n");               break;
    case S_IFLNK:  printf("symlink\n");                 break;
    case S_IFREG:  printf("regular file\n");            break;
    case S_IFSOCK: printf("socket\n");                  break;
    default:       printf("unknown?\n");                break;
    }
    printf("I-node number:            %ju\n", (uintmax_t) sb.st_ino);
    printf("Mode:                     %jo (octal)\n",
           (uintmax_t) sb.st_mode);
    printf("Link count:               %ju\n", (uintmax_t) sb.st_nlink);
    printf("Ownership:                UID=%ju   GID=%ju\n",
           (uintmax_t) sb.st_uid, (uintmax_t) sb.st_gid);
    printf("Preferred I/O block size: %jd bytes\n",
           (intmax_t) sb.st_blksize);
    printf("File size:                %jd bytes\n",
           (intmax_t) sb.st_size);
    printf("Blocks allocated:         %jd\n",
           (intmax_t) sb.st_blocks);
    printf("Last status change:       %s", ctime(&sb.st_ctime));
    printf("Last file access:         %s", ctime(&sb.st_atime));
    printf("Last file modification:   %s", ctime(&sb.st_mtime));
    exit(EXIT_SUCCESS);
}

ls(1), stat(1), access(2), chmod(2), chown(2), readlink(2), statx(2), utime(2), stat(3type), capabilities(7), inode(7), symlink(7)