intro.2

Unix操作系统minix 2.0源码

system.
.en 39 ENOTEMPTY "Directory not empty"
A directory with entries other than \*(lq.\*(rq and \*(lq..\*(rq
was supplied to a remove directory or rename call.
.en 40 ELOOP "Too many symbolic links"
A path name lookup involved more than SYMLOOP symbolic links.  SYMLOOP
equals 8 as distributed.
(Minix-vmd)
.en 50 EPACKSIZE "Invalid packet size
.en 51 EOUTOFBUFS "Not enough buffers left
.en 52 EBADIOCTL "Illegal ioctl for device
.en 53 EBADMODE "Bad mode in ioctl
.en 54 EWOULDBLOCK "Would block
.en 55 EBADDEST "Bad destination address
.en 56 EDSTNOTRCH "Destination not reachable
.en 57 EISCONN "Already connected
.en 58 EADDRINUSE "Address in use
.en 59 ECONNREFUSED "Connection refused
.en 60 ECONNRESET "Connection reset
.en 61 ETIMEDOUT "Connection timed out
.en 62 EURG "Urgent data present
.en 63 ENOURG "No urgent data present
.en 64 ENOTCONN "No connection
.en 65 ESHUTDOWN "Already shutdown
.en 66 ENOCONN "No such connection
.en 67 EINPROGRESS "Operation now in progress
.en 68 EALREADY "Operation already in progress
.ig
.en XXX EDQUOT "Disc quota exceeded"
A 
.B write
to an ordinary file, the creation of a
directory or symbolic link, or the creation of a directory
entry failed because the user's quota of disk blocks was
exhausted, or the allocation of an inode for a newly
created file failed because the user's quota of inodes
was exhausted.
.en XXX ESTALE "Stale NFS file handle"
A client referenced a an open file, when the file has been deleted.
.en XXX EREMOTE "Too many levels of remote in path"
An attempt was made to remotely mount a file system into a path which
already has a remotely mounted component.
..
.SH DEFINITIONS
.TP 5
Process ID
.br
Each active process in the system is uniquely identified by a positive
integer called a process ID.  The range of this ID is from 1 to 29999.
The special process with process ID 1 is
.BR init ,
the ancestor of all processes.
.TP 5
Parent process ID
.br
A new process is created by a currently active process; (see
.BR fork (2)).
The parent process ID of a process is the process ID of its creator,
unless the creator dies, then
.B init
becomes the parent of the orphaned process.
.TP 5
Process Group ID
.br
Each active process is a member of a process group that is identified by
a positive integer called the process group ID.  This is the process
ID of the group leader.  This grouping permits the signaling of related
processes (see
.BR kill (2)).
.TP 5
Real User ID and Real Group ID
.br
Each user on the system is identified by a positive integer
termed the real user ID.
.IP
Each user is also a member of one or more groups.
One of these groups is distinguished from others and
used in implementing accounting facilities.  The positive
integer corresponding to this distinguished group is termed 
the real group ID.
(Under standard Minix this is the only group a process can be a member of.)
.IP
All processes have a real user ID and real group ID.
These are initialized from the equivalent attributes
of the process that created it.
.TP 5
Effective User Id, Effective Group Id, and Access Groups
.br
Access to system resources is governed by three values:
the effective user ID, the effective group ID, and the
group access list.
.IP
The effective user ID and effective group ID are initially the
process's real user ID and real group ID respectively.  Either
may be modified through execution of a set-user-ID or set-group-ID
file (possibly by one its ancestors) (see
.BR execve (2)).
.IP
The group access list is an additional set of group ID's
used only in determining resource accessibility.  Access checks
are performed as described below in ``File Access Permissions''.
The maximum number of additional group ID's is NGROUPS_MAX.
For Minix this is 0, but Minix-vmd supports a list of up to 16
additional group ID's.  (Also known as ``supplemental'' group ID's.)
.TP 5
Super-user
.br
A process is recognized as a
.I super-user
process and is granted special privileges if its effective user ID is 0.
.TP 5
Descriptor
.br
An integer assigned by the system when a file or device is referenced
by
.BR open (2),
.BR dup (2)
or
.BR fcntl (2)
which uniquely identifies an access path to that file or device from
a given process or any of its children.
.TP 5
File Descriptor
Older, and often used name for a descriptor.
.TP 5
File Name
.br
Names consisting of up to NAME_MAX characters may be used to name
an ordinary file, special file, or directory.  NAME_MAX is the maximum
of the maximum file name lengths of the supported file systems.
Excess characters are ignored when too long file names are used for
files in a given file system.
The maximum file name length of the V1 and V2 file systems
is 14 characters.  The Minix-vmd "flex" variants of V1 and V2 have a
60 character maximum.
.IP
The characters in a file name may assume any value representable in
eight bits excluding 0 (null) and the ASCII code for / (slash).
.IP
Note that it is generally unwise to use one of \e'"<>();~$^&*|{}[]?
as part of file names because of the special meaning attached to these
characters by the shell.
.TP 5
Path Name
.br
A path name is a null-terminated character string starting with an
optional slash (/), followed by zero or more directory names separated
by slashes, optionally followed by a file name.
The total length of a path name must be less than PATH_MAX characters
(255 as distributed.)
.IP
If a path name begins with a slash, the path search begins at the
.I root
directory.
Otherwise, the search begins from the current working directory.
A slash by itself names the root directory.  A null pathname is
illegal, use "." to refer to the current working directory.
.TP 5
Directory
.br
A directory is a special type of file that contains entries
that are references to other files.
Directory entries are called links.  By convention, a directory
contains at least two links, . and .., referred to as
.I dot
and
.I dot-dot
respectively.  Dot refers to the directory itself and
dot-dot refers to its parent directory.
.TP 5
Root Directory and Current Working Directory
.br
Each process has associated with it a concept of a root directory
and a current working directory for the purpose of resolving path
name searches.  A process's root directory need not be the root
directory of the root file system.
.TP 5
File Access Permissions
.br
Every file in the file system has a set of access permissions.
These permissions are used in determining whether a process
may perform a requested operation on the file (such as opening
a file for writing).  Access permissions are established at the
time a file is created.  They may be changed at some later time
through the 
.BR chmod (2)
call. 
.IP
File access is broken down according to whether a file may be: read,
written, or executed.  Directory files use the execute
permission to control if the directory may be searched. 
.IP
File access permissions are interpreted by the system as
they apply to three different classes of users: the owner
of the file, those users in the file's group, anyone else.
Every file has an independent set of access permissions for
each of these classes.  When an access check is made, the system
decides if permission should be granted by checking the access
information applicable to the caller.
.IP
Read, write, and execute/search permissions on
a file are granted to a process if:
.IP
The process's effective user ID is that of the super-user.
.IP
The process's effective user ID matches the user ID of the owner
of the file and the owner permissions allow the access.
.IP
The process's effective user ID does not match the user ID of the
owner of the file, and either the process's effective
group ID matches the group ID
of the file, or the group ID of the file is in
the process's group access list,
and the group permissions allow the access.
.IP
Neither the effective user ID nor effective group ID
and group access list of the process
match the corresponding user ID and group ID of the file,
but the permissions for ``other users'' allow access.
.IP
Otherwise, permission is denied.
.SH SEE ALSO
.BR intro (3),
.BR strerror (3).