STAT(2) 							System Calls Manual							   STAT(2)

NAME

       stat, fstat, wstat, fwstat, dirstat, dirfstat, dirwstat, dirfwstat - get and put file status

SYNOPSIS

       #include <u.h>
       #include <libc.h>

       int stat(char *name, char *edir)

       int fstat(int fd, char *edir)

       int wstat(char *name, char *edir)

       int fwstat(int fd, char *edir)

       int dirstat(char *name, Dir *dir)

       int dirfstat(int fd, Dir *dir)

       int dirwstat(char *name, Dir *dir)

       int dirfwstat(int fd, Dir *dir)

DESCRIPTION

       Given  a  file's  name,	or an open file descriptor fd, these routines retrieve or modify file status information.  Stat, fstat, wstat, and
       fwstat are the system calls; they deal with machine-independent directory entries.  Their format is defined by  stat(5).   Stat	and  fstat
       retrieve  information about name or fd into edir, a buffer of length DIRLEN, defined in <libc.h>.  Wstat and fwstat write information back,
       thus changing file attributes according to edir.

       Dirstat, dirfstat, dirwstat, and dirfwstat are the same as their counterparts, except that they operate on Dir structures:

	      typedef
	      struct Dir {
		    char    name[NAMELEN];   /* last element of path */
		    char    uid[NAMELEN];    /* owner name */
		    char    gid[NAMELEN];    /* group name */
		    Qid     qid;	     /* unique id from server */
		    long    mode;	     /* permissions */
		    long    atime;	     /* last read time */
		    long    mtime;	     /* last write time */
		    Length;		     /* file length: see <u.h> */
		    ushort  type;	     /* server type */
		    ushort  dev;	     /* server subtype */
	      } Dir;

       This structure, the Qid structure, NAMELEN, and DIRLEN are defined in <libc.h>.	 The  Length  structure  is  defined  in  </$objtype/u.h>.
       Length  is  an unnamed structure (see 2c(1)), which means that its fields are directly accessible; if the length is known to fit in a long,
       then use length as a field name to retrieve it.	If the file resides on permanent storage and is not a directory, the  length  returned	by
       stat  is  the number of bytes in the file.  For directories, the length returned is zero.  For files that are streams (e.g., pipes and net-
       work connections), the length is the number of bytes that can be read without blocking.

       Each file is the responsibility of some server: it could be a file server, a kernel device, or a user process.  Type identifies the  server
       type,  and  dev says which of a group of servers of the same type is the one responsible for this file.	Qid is a structure containing path
       and vers fields, each an unsigned long: path is guaranteed to be unique among all path names currently on the file server, and vers changes
       each time the file is modified.	Thus, if two files have the same type, dev, and qid they are the same file.

       The bits in mode are defined by

	     0x80000000   directory
	     0x40000000   append only
	     0x20000000   exclusive use (locked)

		   0400   read permission by owner
		   0200   write permission by owner
		   0100   execute permission (search on directory) by owner
		   0070   read, write, execute (search) by group
		   0007   read, write, execute (search) by others

       There  are  constants  defined in <libc.h> for these bits: CHDIR, CHAPPEND, and CHEXCL for the first three; and CHREAD, CHWRITE, and CHEXEC
       for the read, write, and execute bits for others.

       The two time fields are measured in seconds since the epoch (Jan 1 00:00 1970 GMT).  Mtime is the time of the last change of content.  Sim-
       ilarly, atime is set whenever the contents are accessed; also, it is set whenever mtime is set.

       Uid  and gid are the names of the owner and group of the file.  Groups are also users, but each server is free to associate a list of users
       with any user name g, and that list is the set of users in the group g.	When an initial attachment is made to a server, the user string in
       the  process  group is communicated to the server.  Thus, the server knows, for any given file access, whether the accessing process is the
       owner of, or in the group of, the file.	This selects which sets of three bits in mode is used to check permissions.

       Only some of the fields may be changed with the wstat calls.  The name can be changed by anyone with write permission in the parent  direc-
       tory.  The mode and mtime can be changed by the owner or the group leader of the file's current group.  The gid can be changed by the owner
       if he or she is a member of the new group.  The gid can be changed by the group leader of the file's current group if  he  or  she  is  the
       leader of the new group.  (See intro(5) for permission information, and users(6) for user and group information).

SOURCE

       /sys/src/libc/9syscall
	      for the non-dir routines

       /sys/src/libc/9sys
	      for the routines prefixed dir

SEE ALSO

       intro(2), fcall(2), dirread(2), stat(5)

DIAGNOSTICS

       All these functions return 0 on success, -1 on error, and set errstr.

																	   STAT(2)