errno constants

Syntax

#include <errno.h>

Remarks

The errno constants are values assigned to errno for various error conditions.

ERRNO.H contains the definitions of the errno values. However, not all the definitions given in ERRNO.H are used in 32-bit Windows operating systems. Some of the values in ERRNO.H are present to maintain compatibility with the UNIX family of operating systems. The errno values in a 32-bit Windows operating system are a subset of the values for errno in UNIX systems.

The errno value isn't necessarily the same as the actual error code returned by a system call from the Windows operating system. To access the actual operating system error code, use the _doserrno variable, which contains this value.

The following errno values are supported:

Constant	Description	Value
E2BIG	Argument list too long.	7
EACCES	Permission denied. The file's permission setting doesn't allow the specified access. An attempt was made to access a file (or, in some cases, a directory) in a way that's incompatible with the file's attributes. For example, the error can occur when an attempt is made to read from a file that isn't open. Or, on an attempt to open an existing read-only file for writing, or to open a directory instead of a file. Under MS-DOS operating system versions 3.0 and later, EACCES may also indicate a locking or sharing violation. The error can also occur in an attempt to rename a file or directory or to remove an existing directory.	13
EAGAIN	No more processes or not enough memory or maximum nesting level reached. An attempt to create a new process failed because there are no more process slots, or there isn't enough memory, or the maximum nesting level has been reached.	11
EBADF	Bad file number. There are two possible causes: 1) The specified file descriptor isn't a valid value or doesn't refer to an open file. 2) An attempt was made to write to a file or device opened for read-only access.	9
EBUSY	Device or resource busy.	16
ECHILD	No spawned processes.	10
EDEADLK	Resource deadlock would occur.	36
EDEADLOCK	Same as EDEADLK for compatibility with older Microsoft C versions.	36
EDOM	Math argument. The argument to a math function isn't in the domain of the function.	33
EEXIST	Files exists. An attempt has been made to create a file that already exists. For example, the _O_CREAT and _O_EXCL flags are specified in an _open call, but the named file already exists.	17
EFAULT	Bad address.	14
EFBIG	File too large.	27
EILSEQ	Illegal sequence of bytes (for example, in an MBCS string).	42
EINTR	Interrupted function.	4
EINVAL	Invalid argument. An invalid value was given for one of the arguments to a function. For example, the value given for the origin when positioning a file pointer (by a call to fseek) is before the beginning of the file.	22
EIO	I/O error.	5
EISDIR	Is a directory.	21
EMFILE	Too many open files. No more file descriptors are available, so no more files can be opened.	24
EMLINK	Too many links.	31
ENAMETOOLONG	Filename too long.	38
ENFILE	Too many files open in system.	23
ENODEV	No such device.	19
ENOENT	No such file or directory. The specified file or directory doesn't exist or can't be found. This message can occur whenever a specified file doesn't exist or a component of a path doesn't specify an existing directory.	2
ENOEXEC	Exec format error. An attempt was made to execute a file that isn't executable or that has an invalid executable-file format.	8
ENOLCK	No locks available.	39
ENOMEM	Not enough memory is available for the attempted operator. For example, this message can occur when insufficient memory is available to execute a child process, or when the allocation request in a _getcwd call can't be satisfied.	12
ENOSPC	No space left on device. No more space for writing is available on the device (for example, when the disk is full).	28
ENOSYS	Function not supported.	40
ENOTDIR	Not a directory.	20
ENOTEMPTY	Directory not empty.	41
ENOTTY	Inappropriate I/O control operation.	25
ENXIO	No such device or address.	6
EPERM	Operation not permitted.	1
EPIPE	Broken pipe.	32
ERANGE	Result too large. An argument to a math function is too large, resulting in partial or total loss of significance in the result. This error can also occur in other functions when an argument is larger than expected (for example, when the buffer argument to _getcwd is longer than expected).	34
EROFS	Read only file system.	30
ESPIPE	Invalid seek.	29
ESRCH	No such process.	3
EXDEV	Cross-device link. An attempt was made to move a file to a different device (using the rename function).	18
STRUNCATE	A string copy or concatenation resulted in a truncated string. See _TRUNCATE.	80

The following values are supported for compatibility with POSIX:

Constant	Description	Value
EADDRINUSE	Address in use.	100
EADDRNOTAVAIL	Address not available.	101
EAFNOSUPPORT	Address family not supported.	102
EALREADY	Connection already in progress.	103
EBADMSG	Bad message.	104
ECANCELED	Operation canceled.	105
ECONNABORTED	Connection aborted.	106
ECONNREFUSED	Connection refused.	107
ECONNRESET	Connection reset.	108
EDESTADDRREQ	Destination address required.	109
EHOSTUNREACH	Host unreachable.	110
EIDRM	Identifier removed.	111
EINPROGRESS	Operation in progress.	112
EISCONN	Already connected.	113
ELOOP	Too many symbolic link levels.	114
EMSGSIZE	Message size.	115
ENETDOWN	Network down.	116
ENETRESET	Network reset.	117
ENETUNREACH	Network unreachable.	118
ENOBUFS	No buffer space.	119
ENODATA	No message available.	120
ENOLINK	No link.	121
ENOMSG	No message.	122
ENOPROTOOPT	No protocol option.	123
ENOSR	No stream resources.	124
ENOSTR	Not a stream.	125
ENOTCONN	Not connected.	126
ENOTRECOVERABLE	State not recoverable.	127
ENOTSOCK	Not a socket.	128
ENOTSUP	Not supported.	129
EOPNOTSUPP	Operation not supported.	130
EOTHER	Other.	131
EOVERFLOW	Value too large.	132
EOWNERDEAD	Owner dead.	133
EPROTO	Protocol error.	134
EPROTONOSUPPORT	Protocol not supported.	135
EPROTOTYPE	Wrong protocol type.	136
ETIME	Stream timeout.	137
ETIMEDOUT	Timed out.	138
ETXTBSY	Text file busy.	139
EWOULDBLOCK	Operation would block.	140

See also

Global constants