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The
function obtains information about the file pointed to by 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. is like
except in the case where the named file is a symbolic link, in which case
returns information about the link, while 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 that refer to the symbolic link itself are the file type
(S_IFLNK), size, blocks, and link count (always 1). The obtains the same
information about an open file known by the file descriptor The argument
is a pointer to a structure as defined by (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 are as follows: Time when file data
last accessed. Changed by the and system calls. Time when file data last
modified. Changed by the and system calls. Time when file status was
last changed (inode data modification). Changed by the and system
calls. The size-related fields of the are as follows: The optimal I/O
block size for the file. 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 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_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 and
Upon
successful completion a value of 0 is returned. Otherwise, a value of -1
is returned and is set to indicate the error.
Previous versions
of the system used different types for the and fields.
and
will fail if: A component of the path prefix is not a directory. A component
of a pathname exceeded characters, or an entire path name exceeded
characters. The named file does not exist. Search permission is denied
for a component of the path prefix. Too many symbolic links were encountered
in translating the pathname. or points to an invalid address. An I/O
error occurred while reading from or writing to the file system. will
fail if: is not a valid open file descriptor. points to an invalid address.
An I/O error occurred while reading from or writing to the file system.
The fields in the stat structure currently marked and 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
Applying 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.
The and function calls are expected to conform
to
A function call appeared in
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