STAT(5)
NAME
stat, wstat − inquire or change file attributes
SYNOPSIS
Tstat tag[2] fid[2]
Rstat tag[2] fid[2] stat[116]
Twstat tag[2] fid[2] stat[116]
Rwstat tag[2] fid[2]
DESCRIPTION
The stat transaction inquires about the file identified by fid. The reply will contain a 116-byte (DIRLEN in <lib9.h>) machine-independent directory entry laid out as follows:
name[28] file name; must be / if the file is the root directory of the server
uid[28] owner name
gid[28] group name
qid.path[4] the file server’s identification for the file
qid.vers[4] version number for given path
mode[4] permissions and flags
atime[4] last access time
mtime[4] last modification time
length[8] length of file in bytes
type[2] for kernel use
dev[2] for kernel use
Integers in this encoding are in little-endian order (least significant byte first). The convM2D and convD2M routines (see styx(10.2)) convert between directory entries and C structs.
This encoding may be turned into a machine dependent Dir structure (see <lib9.h>) using routines defined in styx(10.2).
The mode contains permission bits as described in intro(5) and 16r80000000 if this file is a directory.
The two time fields are measured in seconds since the epoch (Jan 1 00:00 1970 GMT). The mtime field reflects the time of the last change of content. For a plain file, mtime is the time of the most recent create, open with truncation, or write; for a directory it is the time of the most recent remove, create, or wstat of a file in the directory. Similarly, the atime field records the last read of the contents; also it is set whenever mtime is set. In addition, for a directory, it is set by an attach, walk, or create, all whether successful or not.
The length records the number of bytes in the file. Directories and most files representing devices have a conventional length of 0.
The stat request requires no special permissions.
The wstat request can change some of the file status information. The name can be changed by anyone with write permission in the parent directory; it is an error to change the name to that of an existing file. The mode and mtime can be changed by the owner of the file or the group leader of the file’s current group. The directory bit cannot be changed by a wstat; the other defined permission and mode bits can. The gid can be changed: by the owner if also a member of the new group; or by the group leader of the file’s current group if also leader of the new group (see intro(5) for more information about permissions). None of the other data can be altered by a wstat. In particular, there is no way to change the owner of a file.
A read of a directory yields an integral number of directory entries in the machine independent encoding given above (see read(5)).
ENTRY POINTS
Stat messages are generated by the fstat and stat calls (see sys-stat(2)).
Wstat messages are generated by the fwstat and wstat calls (see sys-stat(2)).