errno.2

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· 2 代码 · 共 375 行

.\" SCCSID: @(#)errno.2	8.3	1/28/91
.TH errno 2
.de en
.HP
\\$1  \\$2  \\$3
.br
..
.SH Name
errno \- introduction error numbers
.SH Syntax
#include <errno.h>
.SH Description
.NXR "errno variable"
The
.PN errno
external variable is set when an error occurs in a system
call.  You can use the value stored in errno to obtain a more detailed
description of the error than is given in the system call's return
value.
The
.PN errno
variable is not cleared on successful system calls, so you should check
its value only when an error is reported.
.SH Return Values
Most system calls have one or more return values.
An error condition is indicated by an otherwise impossible return
value.  This value is almost always \-1. All return codes and values
from system call are of type
.I int,
unless otherwise noted.
.PP
When an error occurs, most calls store one of the
following values, as defined in <errno.h>, in the errno variable:
.NXR "errno error list"
.IP "\fR0\fP" 5 
Unused.
.en 1 EPERM "Not owner
This error indicates
an attempt to modify a file in some way forbidden
except to its owner or the superuser.
It is also returned for attempts
by ordinary users to do things
allowed only to the superuser.
.en 2 ENOENT "No such file or directory
This error occurs when a file name is specified
and the file should exist but does not, or when one
of the directories in a pathname does not exist.
.en 3 ESRCH "No such process
The process whose number was given to 
.PN kill 
and 
.PN ptrace 
does not exist or is already dead.
.en 4 EINTR "Interrupted system call
An asynchronous signal (such as interrupt or quit)
that the program catches 
occurred during a system call.
If execution resumes
after the asynchronous signal is processed,
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 a
.PN read
or
.PN write .
This error may occur
on a call following the one to which it actually applies.
.en 6 ENXIO "No such device or address
I/O on a special file refers to a subdevice that does not
exist or to an area beyond the limits of the device.
This error might also occur when 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 10240 bytes
is presented to 
.PN execve .
.en 8 ENOEXEC "Exec format error
A request is made to execute a file
that does not start with a valid magic number,
although it has the appropriate permissions.
For further information, see 
.MS a.out 5 .
.en 9 EBADF "Bad file number
Either a file descriptor refers to no
open file or a read request is made for a file that is open only
for writing. Likewise, a write request made to a file open only for
reading causes this error.
.en 10 ECHILD "No children
The program issued a
.PN wait
call and the process has no
active or unwaited-for children.
.en 11 EAGAIN "No more processes
In a
.I fork,
the system's process table is full
or the user is not allowed to create any more
processes.
.en 12 ENOMEM "Not enough core
During an 
.PN execve 
or 
.PN brk ,
a program asks for more core or swap space than the system is
able to supply.
A lack of swap space is normally a temporary condition.  However,
a lack of core
is not a temporary condition; the maximum size
of the text, data, and stack segments is a system parameter.
.en 13 EACCES "Permission denied
The call attempts to access a file in some way forbidden
by the protection system.
.en 14 EFAULT "Bad address
The system encountered a hardware fault in attempting to
access the arguments of a system call.
.en 15 ENOTBLK "Block device required
The call specifies a plain file where a block device is required.
.en 16 EBUSY "Mount device busy
The call attempts to mount a device that was already mounted
or to unmount a device
on which there was an active file directory, an
open file, current directory, mounted-on file, or active text segment.
Or,
the call attempts to modify a partition table incorrectly.
See the restrictions in 
.MS chpt 8 .
.en 17 EEXIST "File exists
An existing file is mentioned in an inappropriate context.
.en 18 EXDEV "Cross-device link
The call attempts to form a hard link to a file on another device.
.en 19 ENODEV "No such device
The call attempts to perform an invalid operation on a device, such as
write to a read-only device.
.en 20 ENOTDIR "Not a directory
A file that is not a directory is specified where a directory
is required,
for example, in a pathname or
as an argument to 
.PN chdir .
.en 21 EISDIR "Is a directory
The call attempts to write on a directory.
.en 22 EINVAL "Invalid argument
An invalid argument is specified.
For example, the call might specify dismounting a device that is not mounted 
or reading or writing a file for which
.PN seek
has generated a negative pointer.
This error is also set by math functions, as described in the 
.MS intro 3 
reference page.
.en 23 ENFILE "File table overflow
The system's table of open files is full,
and temporarily no more
.PN open
calls can be processed.
.en 24 EMFILE "Too many open files
The process has opened too many files. The customary configuration limit is 64 
files per process.
.en 25 ENOTTY "Not a typewriter
The file named in an 
.PN ioctl 
call is not a terminal or one of the other
devices to which the call applies.
.en 26 ETXTBSY "Text file busy
The call attempts to execute a pure-procedure
program that is currently open for writing
or reading.
Or, the call attempts to open for writing a pure-procedure
program that is being executed.
.en 27 EFBIG "File too large
The size of a file exceeds the maximum (about
.if t 10\u\s-29\s+2\d
.if n 1.0E9
bytes).
.en 28 ENOSPC "No space left on device
A device runs out of space during a write to an ordinary file.
.en 29 ESPIPE "Illegal seek
An 
.PN lseek 
call specifies a pipe or other device that 
.PN lseek
does not support.
.en 30 EROFS "Restricted operation on a file system
The call attempts to access a file or directory
on a mounted file system when that permission has been revoked. 
For example, the call attempts to write a file on a file system mounted 
read only.
.en 31 EMLINK "Too many links
The call attempts to make more than {LINK_MAX} hard links to a file.
.en 32 EPIPE "Broken pipe
The call attempts to write on a pipe or socket for which there is no process
to read the data.
This condition normally generates a signal;
the error is returned if the signal is ignored.
.en 33 EDOM "Argument too large"
The argument of a function in the math package (which is described in
the
.I ULTRIX Reference Pages, Section 3: Subroutines
) is out of the domain of the function.
.en 34 ERANGE "Result too large
The value of a function in the math package (which is described in the
.I ULTRIX Reference Pages, Section 3: Subroutines
) is unrepresentable within machine precision.
.en 35 EWOULDBLOCK "Operation would block"
The call attempts an operation that would cause a process to block 
on an object in nonblocking mode.
For further information, see 
.MS ioctl 2 .
.en 36 EINPROGRESS "Operation now in progress"
The call is performing an operation that takes a long time to complete, such as
a 
.PN connect 
call, on a nonblocking object.
For further information, see 
.MS ioctl 2 .
.en 37 EALREADY "Operation already in progress"
The call attempts an operation on a nonblocking object that already
has an operation in progress.
.en 38 ENOTSOCK "Socket operation on non-socket"
The call attempts to perform a socket-specific operation on an
entity that is not a socket.
.en 39 EDESTADDRREQ "Destination address required"
A required address is omitted from an operation on a socket.
.en 40 EMSGSIZE "Message too long"
A message sent on a socket is larger than the internal message buffer.
.en 41 EPROTOTYPE "Protocol wrong type for socket"
A protocol is specified that does not support the semantics of the
socket type requested. For example, you cannot use the ARPA Internet
UDP protocol with type SOCK_STREAM.
.en 42 ENOPROTOOPT "Protocol not available"
A bad option was specified in a 
.PN getsockopt 
or 
.PN setsockopt 
call.
.en 43 EPROTONOSUPPORT "Protocol not supported"
The protocol has not been configured into the
system or an implementation for it does not exist.
.en 44 ESOCKTNOSUPPORT "Socket type not supported"
The support for the socket type has not been configured into the
system or an implementation for it does not exist.
.en 45 EOPNOTSUPP "Error\-operation not supported"
The call attempts an unsupported operation, such as trying to accept a connection on a datagram socket.
.en 46 EPFNOSUPPORT "Protocol family not supported"
The protocol family has not been configured into the
system or an implementation for it does not exist.
.en 47 EAFNOSUPPORT "Address family not supported by protocol family"
An address incompatible with the requested protocol is specified.
For example, you cannot use PUP
Internet addresses with ARPA Internet protocols.
.en 48 EADDRINUSE "Address already in use"
The call attempts to use an address that is already in use. Each address
can be used only once.  
.en 49 EADDRNOTAVAIL "Cannot assign requested address"
The call attempts to create a socket with an
address not on this machine.
.en 50 ENETDOWN "Network is down"
A socket operation encountered a network that is not operating.
.en 51 ENETUNREACH "Network is unreachable"
A socket operation attempts to reach an unreachable network.
.en 52 ENETRESET "Network dropped connection on reset"
The host to which the program was connected to crashed and rebooted.
.en 53 ECONNABORTED "Software caused connection abort"
A connection abort has occurred internal to your host machine.
.en 54 ECONNRESET "Connection reset by peer"
A connection has been forcibly closed by a peer.  This error usually
results from the peer executing a 
.PN shutdown  
call.
.en 55 ENOBUFS "No buffer space available"
The system lacks sufficient buffer space to perform an operation on a
socket or pipe.
.en 56 EISCONN "Socket is already connected"
A
.PN connect
request names an already connected socket, or
a
.PN sendto
or
.PN sendmsg
request on a connected socket specifies a destination
other than the connected party.
.en 57 ENOTCONN "Socket is not connected"
A request to send or receive data could not complete because
the socket is not connected.
.en 58 ESHUTDOWN "Cannot send after socket shutdown"
A request to send data could not complete because the socket
has already been shut down with a previous 
.PN shutdown  
call.
.en 59 ETOOMANYREFS "Too many references: cannot splice"
.en 60 ETIMEDOUT "Connection timed out"
A
.PN connect
request failed because the connected party did not
properly respond after a period of time.  (The timeout
period is dependent on the communication protocol.)
For example, this error
occurs when an NFS file system is mounted with the ``soft,''
option and the server is not responding to file operation
requests.
.en 61 ECONNREFUSED "Connection refused"
No connection could be made because the target machine actively
refused it.  This error usually results from trying to connect
to a service that is inactive on the remote host.
.en 62 ELOOP "Too many levels of symbolic links"
A pathname lookup involves more than eight symbolic links.
.en 63 ENAMETOOLONG "File name too long"
A component of a path name exceeds 255 characters, or an entire
path name exceeds 1023 characters.
.en 64 EHOSTDOWN "Host is down" 
A socket operation has failed because the destination host is down.
.en 65 EHOSTUNREACH "No route to host"
A socket operation attempts to reach an unreachable host.
.en 66 ENOTEMPTY "Directory not empty"
A directory with entries other than dot (.) and dot-dot (..) is specified 
in a 
.PN rmdir 
or 
.PN rename 
call.
.en 67 EPROCLIM "Too many processes"
Creating the process would cause the user to exceed the number of user 
processes that are
available.  The 
.I maxuprc
option in the configuration file controls this limit.
.en 68 EUSERS "Too many users"
A login process would exceed the
maximum allowable login processes for which the system is
licensed.  
.en 69 EDQUOT "Disk quota exceeded"
A
.PN write
to an ordinary file, the creation of a directory or symbolic
link, or the creation of a directory entry has failed because the
user's quota of disk blocks is exhausted. Or, the allocation
of an inode for a newly created file has failed because the user's
quota of inodes is exhausted.
.en 70 ESTALE "Stale NFS file handle" 
Information used by the operating
system to identify a file in an NFS file system that is no longer  
valid.  This error code results from operating on a remote file
that no longer exists on the server or resides in a file system
that has been moved to a different device on the server.
.en 71 EREMOTE "Too many levels of remote in path"
A remote NFS client has requested an operation on a file
that is remote to the server as well.  An attempt has been 
made to mount an NFS remote file system that is not local to the
specified server.  This error code cannot occur except in response
to a failed 
.PN mount 
call. 
.en 72 ENOMSG "No message of desired type"
An attempt was made to receive a message of a type that does not
exist on the specified message queue.  For further information, see
.MS msgop 2 .
.en 73 EIDRM "Identifier removed"
In semaphores, shared memory, or message queues, the caller
tried to access the identifier after it had been removed
from the system.
.en 74 EALIGN "Alignment error"
Alignment error of some type has occurred, for example, cluster,
page, or block.
.en 75 ENOLCK "No locks available"
A file locking request could not be fulfilled because a system
limit on the number of active locks would have been exceeded.
.en 76 ENOSYS "Function not implemented"
The requested function is not available in ULTRIX.  Included for
POSIX compatibility only.
.SH See Also
.MS perror 3