stat.2

Unix操作系统minix 2.0源码

.\" Copyright (c) 1980 Regents of the University of California.
.\" All rights reserved.  The Berkeley software License Agreement
.\" specifies the terms and conditions for redistribution.
.\"
.\"	@(#)stat.2	6.5 (Berkeley) 5/12/86
.\"
.TH STAT 2 "May 12, 1986"
.UC 4
.SH NAME
stat, lstat, fstat \- get file status
.SH SYNOPSIS
.nf
.ft B
#include <sys/types.h>
#include <sys/stat.h>

.ta +54n
int stat(const char *\fIpath\fP, struct stat *\fIbuf\fP)
int lstat(const char *\fIpath\fP, struct stat *\fIbuf\fP)	(Minix-vmd)
int fstat(int \fIfd\fP, struct stat *\fIbuf\fP)
.fi
.ft R
.SH DESCRIPTION
.B Stat
obtains information about the file
.IR 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 reachable.
.PP
.B Lstat
is like \fBstat\fP except in the case where the named file is a symbolic link,
in which case
.B lstat
returns information about the link,
while
.B stat
returns information about the file the link references.
(Minix-vmd)
.PP
.B Fstat
obtains the same information about an open file
referenced by the argument descriptor, such as would
be obtained by an \fBopen\fP call.  Pipe descriptors
look like named pipes with a link count of zero.  The
st_size field of pipes or named pipes shows the amount of
bytes currently buffered in the pipe.
.PP
.I Buf
is a pointer to a
.B stat
structure into which information is placed concerning the file.
The contents of the structure pointed to by
.I buf
is as follows:
.PP
.if t .RS
.nf
.ta +0.4i +0.8i +1i
struct stat {
	dev_t	st_dev;	/* device inode resides on */
	ino_t	st_ino;	/* this inode's number */
	mode_t	st_mode;	/* file mode, protection bits, etc. */
	nlink_t	st_nlink;	/* number or hard links to the file */
	uid_t	st_uid;	/* user-id of the file's owner */
	gid_t	st_gid;	/* group-id of the file's owner */
	dev_t	st_rdev;	/* the device type, for inode that is device */
	off_t	st_size;	/* total size of file */
	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 */
};
.fi
.if t .RE
.DT
.PP
.TP 12
st_atime
Time when file data was last read or modified.  Changed by the following system
calls:
.BR mknod (2),
.BR utime (2),
.BR read (2),
and
.BR write (2).
For reasons of efficiency, 
st_atime is not set when a directory
is searched, although this would be more logical.
.TP 12
st_mtime
Time when data was last modified.
It is not set by changes of owner, group, link count, or mode.
Changed by the following system calls:
.BR mknod (2),
.BR utime (2),
.BR write (2).
.TP 12
st_ctime
Time when file status was last changed.
It is set both both by writing and changing the i-node.
Changed by the following system calls:
.BR chmod (2)
.BR chown (2),
.BR link (2),
.BR mknod (2),
.BR rename (2),
.BR unlink (2),
.BR utime (2),
.BR write (2).
.PP
The file type information in \fBst_mode\fP has bits:
.PP
.nf
.in +5n
.ta 1.6i 2.5i 3i
#define S_IFMT	0170000	/* type of file */
#define\ \ \ \ S_IFIFO	0010000	/* named pipe */
#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 (Minix-vmd) */
.fi
.in -5n
.PP
The mode bits 0007777 encode set-uid/gid bits and
permission bits (see
.BR chmod (2)).
.SH "RETURN VALUE
Upon successful completion a value of 0 is returned.
Otherwise, a value of \-1 is returned and
.B errno
is set to indicate the error.
.SH "ERRORS
.B Stat
and
.B lstat
will fail if one or more of the following are true:
.TP 15
[ENOTDIR]
A component of the path prefix is not a directory.
.TP 15
[ENAMETOOLONG]
The path name exceeds PATH_MAX characters.
.TP 15
[ENOENT]
The named file does not exist.
.TP 15
[EACCES]
Search permission is denied for a component of the path prefix.
.TP 15
[ELOOP]
Too many symbolic links were encountered in translating the pathname.
(Minix-vmd)
.TP 15
[EFAULT]
.I Buf
or
.I name
points to an invalid address.
.TP 15
[EIO]
An I/O error occurred while reading from or writing to the file system.
.PP
.B Fstat
will fail if one or both of the following are true:
.TP 15
[EBADF]
.I Fildes
is not a valid open file descriptor.
.TP 15
[EFAULT]
.I Buf
points to an invalid address.
.TP 15
[EIO]
An I/O error occurred while reading from or writing to the file system.
.SH "SEE ALSO"
.BR chmod (2),
.BR chown (2),
.BR utime (2).