SUMMARY
When an error occurs in some library routines, the errno
variable is set to a value that can be used to indicate the nature of the
error. These error codes are defined in the file ERRNO.H. The codes were
originally set up for use with UNIX to conform to errors occurring under that
operating system. Because of this, and the differences between the various
operating systems, many of the codes have no relevance to the MS-DOS and
Windows NT environments.
To maintain compatibility with UNIX and
XENIX, all the codes, whether meaningful or not, are defined in ERRNO.H.
However, in the description of the global variable errno, the CRT documentation
included with each of the above products lists only those codes (and their
meanings) applicable to the corresponding operating system, either MS-DOS or
Windows NT. To output the associated the error messages of these codes, use the
perror() function.
If a returned errno value is not one of the
listed codes, it can be assumed that the error code was generated incorrectly
and is not indicative of the true problem. The documentation for the specific
function used denotes which errno values, if any, may be set by an error in
that function. The following is a listing of all the errno values defined in
ERRNO.H along with brief descriptions of their meanings. Only the values marked
with an asterisk (*) are considered valid under MS-DOS. Those marked with a
plus sign (+) are considered valid under Windows NT.
For more
information on the values not marked with an asterisk or a plus sign, see a
UNIX or XENIX system manual.
Value Define Description
----- ------ -----------
EPERM 1 Not owner
ENOENT 2 *+No such file or directory
ESRCH 3 No such process
EINTR 4 Interrupted system call
EIO 5 I/O error
ENXIO 6 No such device or address
E2BIG 7 *+Argument list too long
ENOEXEC 8 *+Exec format error
EBADF 9 *+Bad file number
ECHILD 10 +No spawned processes
EAGAIN 11 +No more processes; not enough memory;
maximum nesting level reached
ENOMEM 12 *+Not enough memory
EACCES 13 *+Permission denied
EFAULT 14 Bad address
ENOTBLK 15 Block device required
EBUSY 16 Mount device busy
EEXIST 17 *+File exists
EXDEV 18 *+Cross-device link
ENODEV 19 No such device
ENOTDIR 20 Not a directory
EISDIR 21 Is a directory
EINVAL 22 *+Invalid argument
ENFILE 23 File table overflow
EMFILE 24 *+Too many open files
ENOTTY 25 Not a teletype
ETXTBSY 26 Text file busy
EFBIG 27 File too large
ENOSPC 28 *+No space left on device
ESPIPE 29 Illegal seek
EROFS 30 Read-only file system
EMLINK 31 Too many links
EPIPE 32 Broken pipe
EDOM 33 *+Math argument
ERANGE 34 *+Result too large
EUCLEAN 35 File system needs cleaning
EDEADLK 36 +Resource deadlock would occur
EDEADLOCK 36 *Resource deadlock would occur
ENAMETOOLONG 38
ENOLCK 39
ENOSYS 40
ENOTEMPTY 41
EILSEQ 42
* Used under both MS-DOS
+ Used under Windows NT
Note With Visual C++ 32-bit Edition, EDEADLK is the
preferred manifest constant for "resource deadlock." However, EDEADLOCK is
supported for compatibility with older MS-C versions.
For more
information on errno and its possible values, please consult the Visual C++
Book Online.