intro.2

Unix操作系统minix 2.0源码

.\" Copyright (c) 1980,1983,1986 Regents of the University of California.
.\" All rights reserved.  The Berkeley software License Agreement
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.\"	@(#)intro.2	6.7 (Berkeley) 5/23/86
.\"
.TH INTRO 2 "June 30, 1986"
.UC 4
.de en
.HP
\\$1  \\$2  \\$3
.br
..
.SH NAME
intro, errno \- introduction to system calls and error numbers
.SH SYNOPSIS
.B "#include <errno.h>"
.SH DESCRIPTION
This section describes all of the system calls.  Most
of these calls have one or more error returns.
An error condition is indicated by an otherwise impossible return
value.  This is almost always \-1; the individual descriptions
specify the details.
Note that a number of system calls overload the meanings of these
error numbers, and that the meanings must be interpreted according
to the type and circumstances of the call.
.PP
As with normal arguments, all return codes and values from
functions are of type integer unless otherwise noted.
An error number is also made available in the external
variable \fBerrno\fP, which is not cleared
on successful calls.
Thus \fBerrno\fP should be tested only after an error has occurred.
.PP
The following is a complete list of the errors and their
names as given in
.RI < sys/errno.h >:
.en 0 OK "Error 0
Unused.  (The symbol "OK" is only used inside the kernel source.)
.en 1 EPERM "Not owner
Typically this error indicates
an attempt to modify a file in some way forbidden
except to its owner or super-user.
It is also returned for attempts
by ordinary users to do things
allowed only to the super-user.
.en 2 ENOENT "No such file or directory
This error occurs when a file name is specified
and the file should exist but doesn't, or when one
of the directories in a path name does not exist.
.en 3 ESRCH "No such process
The process or process group whose number was given
does not exist, or any such process is already dead.
.en 4 EINTR "Interrupted system call
An asynchronous signal (such as interrupt or quit)
that the user has elected to catch
occurred during a system call.
If execution is resumed
after processing the signal
and the system call is not restarted,
it will appear as if the interrupted system call
returned this error condition.
.en 5 EIO "I/O error
Some physical I/O error occurred during an I/O operation, usually
.B read
or
.BR write .
Operations on file descriptors that refer to devices that are forcefully
taken away or in a bad state will also provoke this error.
.en 6 ENXIO "No such device or address
I/O on a special file refers to a subdevice that does not
exist,
or beyond the limits of the device.
It may also occur when, for example, an illegal tape drive
unit number is selected 
or a disk pack is not loaded on a drive.
.en 7 E2BIG "Arg list too long
An argument list longer than ARG_MAX bytes is presented to
.BR execve .
ARG_MAX is set to 4096 bytes for 16-bit Minix, 16384 bytes for 32-bit
Minix, and unlimited for Minix-vmd as these systems are released.
.en 8 ENOEXEC "Exec format error
A request is made to execute a file
that, although it has the appropriate permissions,
does not start with a valid magic number, (see
.BR a.out (5)).
.en 9 EBADF "Bad file number
Either a file descriptor refers to no
open file,
or a read (resp. write) request is made to
a file that is open only for writing (resp. reading).
.en 10 ECHILD "No children
.B Wait
and the process has no
living or unwaited-for children.
.en 11 EAGAIN "Resource temporarily unavailable
In a
.B fork,
the system's process table is full or the user is not allowed to create
any more processes, otherwise an operation that would cause a process to
block was attempted on an object in non-blocking mode (see \fBfcntl\fP(2)).
.en 12 ENOMEM "Not enough core
During an
.B execve
or
.B brk,
a program asks for more (virtual) memory than the system is
able to supply,
or a process size limit would be exceeded.
The maximum size
of the data+stack segment is set by the
.BR chmem (1)
program.  For Minix-vmd a small data+stack size is increased to 3 megabytes
when a program is executed.
.en 13 EACCES "Permission denied
An attempt was made to access a file in a way forbidden
by the protection system.  Also an attempt to open a device for writing
that is physically write protected.
.en 14 EFAULT "Bad address
An argument of a system call is outside the address space allocated to a
process.
.en 15 ENOTBLK "Block device required
A plain file was mentioned where a block device was required,
e.g., in
.BR mount .
.en 16 EBUSY "Resource busy
An attempt to mount a device that was already mounted or
an attempt was made to dismount a device
on which there is an active file
(open file, current directory, mounted-on file, or active text segment).
A request was made to an exclusive access device that was already in use.
.en 17 EEXIST "File exists
An existing file was mentioned in an inappropriate context,
e.g.,
.BR link .
.en 18 EXDEV "Cross-device link
A hard link to a file on another device
was attempted.
.en 19 ENODEV "No such device
An attempt was made to access a device that is not configured by the system,
i.e., there is no driver for the device.
.en 20 ENOTDIR "Not a directory
A non-directory was specified where a directory
is required,
for example, in a path name or
as an argument to
.BR chdir .
.en 21 EISDIR "Is a directory
An attempt to write on a directory.
.en 22 EINVAL "Invalid argument
Some invalid argument:
dismounting a non-mounted
device,
mentioning an unknown signal in
.B signal,
or some other argument inappropriate for the call.
Also set by math functions, (see 
.BR math (3)).
.en 23 ENFILE "File table overflow
The system's table of open files is full,
and temporarily no more
.I opens
can be accepted.
.en 24 EMFILE "Too many open files
The limit on the number of open files per process, OPEN_MAX, is reached.
As released, this limit is 20 for Minix, and 30 for Minix-vmd.
.en 25 ENOTTY "Not a typewriter
The file mentioned in an
.B ioctl
is not a terminal or one of the
devices to which this call applies.  (Often seen error from programs with
bugs in their error reporting code.)
.en 26 ETXTBSY "Text file busy
Attempt to execute a program that is open for writing.  Obsolete under Minix.
.en 27 EFBIG "File too large
The size of a file exceeded the maximum (little over 64 megabytes for
the V2 file system).
.en 28 ENOSPC "No space left on device
A
.B write
to an ordinary file, the creation of a
directory or symbolic link, or the creation of a directory
entry failed because no more disk blocks are available
on the file system, or the allocation of an inode for a newly
created file failed because no more inodes are available
on the file system.
.en 29 ESPIPE "Illegal seek
An
.B lseek
was issued to a pipe or TCP/IP channel.
This error may also be issued for
other non-seekable devices.
.en 30 EROFS "Read-only file system
An attempt to modify a file or directory
was made
on a device mounted read-only.
.en 31 EMLINK "Too many links
An attempt to make more than a certain number of hard links to a file.  The
advertized maximum, LINK_MAX, is 127, but Minix-vmd uses a much larger
maximum of 32767 for the V2 file system.
.en 32 EPIPE "Broken pipe
A write on a pipe or TCP/IP channel for which there is no process
to read the data.
This condition normally generates the signal SIGPIPE;
the error is returned if the signal is caught or ignored.
.en 33 EDOM "Math argument
The argument of a function in the math package
is out of the domain of the function.
.en 34 ERANGE "Result too large
The value of a function in the math package
is unrepresentable within machine precision.
.en 35 EDEADLK "Resource deadlock avoided
A process attempts to place a blocking lock on a file that is already
locked by another process and that process is waiting for the first
process to unlock a file that first process already has a lock on.
(The classic "lock A, lock B" by process 1, and "lock B, lock A" by
process 2.)
.en 36 ENAMETOOLONG "File name too long"
The path name exceeds PATH_MAX characters.  PATH_MAX equals 255 as
distributed.
.en 37 ENOLCK "No locks available
The system's table of active locks is full.
.en 38 ENOSYS "Function not implemented
The system call is not supported.  Either an old program uses an obsolete
call, or a program for a more capable system is run on a less capable