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fstatat (2)

>> fstatat (2) ( Solaris man: Системные вызовы )

fstatat (2) ( Linux man: Системные вызовы )

NAME

stat, lstat, fstat, fstatat - get file status

SYNOPSIS

#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>

int stat(const char *restrict path, struct stat *restrict buf);

int lstat(const char *restrict path, struct stat *restrict buf);

int fstat(int fildes, struct stat *buf);

int fstatat(int fildes, const char *path, struct stat *buf,
    int flag);

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.

The lstat() function obtains file attributes similar to stat(), except when the named file is a symbolic link; in that case lstat() returns information about the link, while stat() returns information about the file the link references.

The fstat() function obtains information about an open file known by the file descriptor fildes, obtained from a successful open(2), creat(2), dup(2), fcntl(2), or pipe(2) function. If fildes references a shared memory object, the system updates in the stat structure pointed to by the buf argument only the st_uid, st_gid, st_size, and st_mode fields, and only the S_IRUSR, S_IWUSR, S_IRGRP, S_IWGRP, S_IROTH, and S_IWOTH file permission bits need be valid. The system can update other fields and flags. The fstat() function updates any pending time-related fields before writing to the stat structure.

The fstatat() function obtains file attributes similar to the stat(), lstat(), and fstat() functions. If the path argument is a relative path, it is resolved relative to the fildes argument rather than the current working directory. If path is absolute, the fildes argument is unused. If the fildes argument has the special value AT_FDCWD, relative paths are resolved from the current working directory. If AT_SYMLINK_NOFOLLOW is set in the flag argument, the function behaves like lstat() and does not automatically follow symbolic links. See fsattr(5). If _ATTR_TRIGGER is set in the flag argument and the vnode is a trigger mount point, the mount is performed and the function returns the attributes of the root of the mounted filesystem.

The buf argument is a pointer to a stat structure into which information is placed concerning the file. A stat structure includes the following members:

mode_t   st_mode;          /* File mode (see mknod(2)) */
ino_t    st_ino;           /* Inode number */
dev_t    st_dev;           /* ID of device containing */
                          /* a directory entry for this file */
dev_t    st_rdev;          /* ID of device */
                          /* This entry is defined only for */
                          /* char special or block special files */
nlink_t  st_nlink;         /* Number of links */
uid_t    st_uid;           /* User ID of the file's owner */
gid_t    st_gid;           /* Group ID of the file's group */
off_t    st_size;          /* File size in bytes */
time_t   st_atime;         /* Time of last access */
time_t   st_mtime;         /* Time of last data modification */
time_t   st_ctime;         /* Time of last file status change */
                          /* Times measured in seconds since */
                          /* 00:00:00 UTC, Jan. 1, 1970 */
long     st_blksize;       /* Preferred I/O block size */
blkcnt_t st_blocks;        /* Number of 512 byte blocks allocated*/
char     st_fstype[_ST_FSTYPSZ];
                          /* Null-terminated type of filesystem */

Descriptions of structure members are as follows:

st_mode

: The mode of the file as described for the mknod() function. In addition to the modes described on the mknod(2) manual page, the mode of a file can also be S_IFSOCK if the file is a socket, S_IFDOOR if the file is a door, S_IFPORT if the file is an event port, or S_IFLNK if the file is a symbolic link. S_IFLNK can be returned either by lstat() or by fstat() when the AT_SYMLINK_NOFOLLOW flag is set.

st_ino

: This field uniquely identifies the file in a given file system. The pair st_ino and st_dev uniquely identifies regular files.

st_dev

: This field uniquely identifies the file system that contains the file. Its value may be used as input to the ustat() function to determine more information about this file system. No other meaning is associated with this value.

st_rdev

: This field should be used only by administrative commands. It is valid only for block special or character special files and only has meaning on the system where the file was configured.

st_nlink

: This field should be used only by administrative commands.

st_uid

: The user ID of the file's owner.

st_gid

: The group ID of the file's group.

st_size

: For regular files, this is the address of the end of the file. For block special or character special, this is not defined. See also pipe(2).

st_atime

: Time when file data was last accessed. Some of the functions that change this member are: creat(), mknod(), pipe(), utime(2), and read(2).

st_mtime

: Time when data was last modified. Some of the functions that change this member are: creat(), mknod(), pipe(), utime(), and write(2).

st_ctime

: Time when file status was last changed. Some of the functions that change this member are: chmod(2), chown(2), creat(2), link(2), mknod(2), pipe(2), rename(2), unlink(2), utime(2), and write(2).

st_blksize

: A hint as to the "best" unit size for I/O operations. This field is not defined for block special or character special files.

st_blocks

: The total number of physical blocks of size 512 bytes actually allocated on disk. This field is not defined for block special or character special files.

st_fstype

: A null-teminated string that uniquely identifies the type of the filesystem that contains the file.

RETURN VALUES

Upon successful completion, 0 is returned. Otherwise, -1 is returned and errno is set to indicate the error.

ERRORS

The stat(), fstat(), lstat(), and fstatat() functions will fail if:

EIO

: An error occurred while reading from the file system.

EOVERFLOW

: The file size in bytes or the number of blocks allocated to the file or the file serial number cannot be represented correctly in the structure pointed to by buf.

The stat(), lstat(), and fstatat() functions will fail if:

EACCES

: Search permission is denied for a component of the path prefix.

EFAULT

: The buf or path argument points to an illegal address.

EINTR

: A signal was caught during the execution of the stat() or lstat() function.

ELOOP

: A loop exists in symbolic links encountered during the resolution of the path argument.

ENAMETOOLONG

: The length of the path argument exceeds {PATH_MAX}, or the length of a path component exceeds {NAME_MAX} while _POSIX_NO_TRUNC is in effect.

ENOENT

: A component of path does not name an existing file or path is an empty string.

ENOLINK

: The path argument points to a remote machine and the link to that machine is no longer active.

ENOTDIR

: A component of the path prefix is not a directory, or the fildes argument does not refer to a valid directory when given a non-null relative path.

The fstat() and fstatat() functions will fail if:

EBADF

: The fildes argument is not a valid open file descriptor. The fildes argument to fstatat() can also have the valid value of AT_FDCWD.

EFAULT

: The buf argument points to an illegal address.

EINTR

: A signal was caught during the execution of the fstat() function.

ENOLINK

: The fildes argument points to a remote machine and the link to that machine is no longer active.

The stat(), fstat(), and lstat() functions may fail if:

EOVERFLOW

: One of the members is too large to store in the stat structure pointed to by buf.

The stat() and lstat() functions may fail if:

ELOOP

: More than {SYMLOOP_MAX} symbolic links were encountered during the resolution of the path argument.

ENAMETOOLONG

: As a result of encountering a symbolic link in resolution of thepath argument, the length of the substituted pathname strings exceeds {PATH_MAX}.

The stat() and fstatat() functions may fail if:

ENXIO

: The path argument names a character or block device special file and the corresponding I/O device has been retired by the fault management framework.

EXAMPLES

Example 1 Use stat() to obtain file status information.

The following example shows how to obtain file status information for a file named /home/cnd/mod1. The structure variable buffer is defined for the stat structure.

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
struct stat buffer;
int         status;
...
status = stat("/home/cnd/mod1", &buffer);

Example 2 Use stat() to get directory information.

The following example fragment gets status information for each entry in a directory. The call to the stat() function stores file information in the stat structure pointed to by statbuf. The lines that follow the stat() call format the fields in the stat structure for presentation to the user of the program.

#include <sys/types.h>
#include <sys/stat.h>
#include <dirent.h>
#include <pwd.h>
#include <grp.h>
#include <time.h>
#include <locale.h>
#include <langinfo.h>
#include <stdio.h>
#include <stdint.h>
struct dirent *dp;
struct stat   statbuf;
struct passwd *pwd;
struct group  *grp;
struct tm     *tm;
char          datestring[256];
...
/* Loop through directory entries */
while ((dp = readdir(dir)) != NULL) {
   /* Get entry's information. */
   if (stat(dp->d_name, &statbuf) == -1)
   continue;

    /* Print out type, permissions, and number of links. */
    printf("%10.10s", sperm (statbuf.st_mode));
    printf("%4d", statbuf.st_nlink);

    /* Print out owners name if it is found using getpwuid(). */
    if ((pwd = getpwuid(statbuf.st_uid)) != NULL)
       printf(" %-8.8s", pwd->pw_name);
    else
       printf(" %-8d", statbuf.st_uid);

    /* Print out group name if it's found using getgrgid(). */
    if ((grp = getgrgid(statbuf.st_gid)) != NULL)
       printf(" %-8.8s", grp->gr_name);
    else
       printf(" %-8d", statbuf.st_gid);

    /* Print size of file. */
    printf(" %9jd", (intmax_t)statbuf.st_size);
    tm = localtime(&statbuf.st_mtime);

    /* Get localized date string. */
    strftime(datestring, sizeof(datestring), nl_langinfo(D_T_FMT), tm);

    printf(" %s %s\n", datestring, dp->d_name);
}

Example 3 Use fstat() to obtain file status information.

The following example shows how to obtain file status information for a file named /home/cnd/mod1. The structure variable buffer is defined for the stat structure. The /home/cnd/mod1 file is opened with read/write privileges and is passed to the open file descriptor fildes.

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
struct stat buffer;
int         status;
...
fildes = open("/home/cnd/mod1", O_RDWR);
status = fstat(fildes, &buffer);

Example 4 Use lstat() to obtain symbolic link status information.

The following example shows how to obtain status information for a symbolic link named /modules/pass1. The structure variable buffer is defined for the stat structure. If the path argument specified the filename for the file pointed to by the symbolic link (/home/cnd/mod1), the results of calling the function would be the same as those returned by a call to the stat() function.

#include <sys/stat.h>
struct stat buffer;
int         status;
...
status = lstat("/modules/pass1", &buffer);

USAGE

If chmod() or fchmod() is used to change the file group owner permissions on a file with non-trivial ACL entries, only the ACL mask is set to the new permissions and the group owner permission bits in the file's mode field (defined in mknod(2)) are unchanged. A non-trivial ACL entry is one whose meaning cannot be represented in the file's mode field alone. The new ACL mask permissions might change the effective permissions for additional users and groups that have ACL entries on the file.

The stat(), fstat(), and lstat() functions have transitional interfaces for 64-bit file offsets. See lf64(5).