errno(2) System Calls Manual errno(2)
errno - error indicator for function calls
Many functions in the HP-UX operating system indicate an error condition by returning an otherwise out-of-range value (usually Most of
these functions set the symbol that is defined in to a nonzero code value that more specifically identifies the particular error condition
that was encountered.
In most cases, the manpages for functions that set list those values and error descriptions in the ERRORS section of the manpages. How-
ever, failures in underlying functions, subsystems, and applications may return values that are not documented in the calling functions'
The value of is zero immediately after a successful call to any of the functions described by exec(2), but it is never set to zero by any
other HP-UX function. Functions for which the use of is not described may nevertheless change its value to a nonzero value.
Since is not cleared on successful function calls, its value should be checked or used only when an error has been indicated and when the
function's section documents the error codes.
Applications should not attempt to take the address of The practice of defining as is obsolescent.
The following is a complete list of the error codes. The numeric values can be found in but they should not be used in an application pro-
gram because they can vary from system to system.
[E2BIG] Arg list too long. An argument and or environment list longer than maximum supported size is presented to a member of the
family. Other possibilities include: message size or number of semaphores exceeds system limit or too many privileged
groups have been set up
[EACCES] Permission denied. An attempt was made to access a file or IPC object in a way forbidden by the protection system.
[EADDRINUSE] Address already in use. Only one usage of each address is normally permitted.
Cannot assign requested address. Normally results from an attempt to create a socket with an address not on this machine.
[EAFNOSUPPORT] Address family not supported by protocol family. An address incompatible with the requested protocol was used. For exam-
ple, you should not necessarily expect to be able to use PUP Internet addresses with ARPA Internet protocols.
[EAGAIN] Resource temporarily unavailable. This is likely a temporary condition, and later calls to the same routine may complete
[EALREADY] Operation already in progress. An operation was attempted on a nonblocking object which already had an operation in
[EBADF] Bad file number. Either a file descriptor refers to no open file, a read (respectively write) request is made to a file
which is open only for writing (respectively reading), or the file descriptor is not in the legal range of file descriptors.
[EBUSY] Device or 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, active text segment). It will also occur
if an attempt is made to enable accounting when it is already enabled. The device or resource is currently unavailable,
such as when a nonsharable device file is in use.
[ECHILD] No child processes. A was executed by a process that had no existing or unwaited-for child processes.
[ECONNABORTED] Software caused connection abort. A connection abort was caused internal to your host machine.
[ECONNREFUSED] Connection refused. No connection could be made because the target machine actively refused it. This usually results from
trying to connect to a service that is inactive on the foreign host.
[ECONNRESET] Connection reset by peer. A connection was forcibly closed by a peer. This normally results from the peer executing a call
[EDEADLK] Resource deadlock would occur. A process which has locked a system resource would have been put to sleep while attempting
to access another process' locked resource.
[EDESTADDRREQ] Destination address required. A required address was omitted from an operation on a socket.
[EDOM] Math argument. The argument of a function in the math package(3M) is out of the domain of the function.
[EEXIST] File exists. An existing file was mentioned in an inappropriate context; e.g.,
[EFAULT] Bad address. The system encountered a hardware fault in attempting to use an argument of a system call; can also result
from passing the wrong number of parameters to a system call. The reliable detection of this error is implementation depen-
[EFBIG] File too large. The size of a file exceeded the maximum file size (for the file system) or was exceeded (see ulimit(2)), or
a bad semaphore number in a call (see semop(2)).
[EHOSTDOWN] Host is down. A socket operation encountered a dead host. Networking activity on the local host has not been initiated.
[EHOSTUNREACH] No route to host. A socket operation was attempted to an unreachable host.
[EIDRM] Identifier Removed. This error is returned to processes that resume execution due to the removal of an identifier from the
file system's name space (see msgctl(2), semctl(2), and shmctl(2)).
[EILSEQ] Illegal byte sequence. A wide character code has been detected that does not correspond to a valid character, or a byte
sequence does not form a valid wide character code.
[EINPROGRESS] Operation now in progress. An operation that takes a long time to complete was attempted on a nonblocking object (see
ioctl(2) and fcntl(2)).
[EINTR] Interrupted system call. An asynchronous signal (such as interrupt or quit), which the user has elected to catch, occurred
during a system call. If execution is resumed after processing the signal, it will appear as if the interrupted system call
returned this error condition unless the system call is restarted (see signal(5)).
[EINVAL] Invalid argument. Some invalid argument (such as unmounting a device that is not currently mounted, mentioning an undefined
signal in or or reading or writing a file for which has generated a negative pointer). Also set by the math functions
described in the(3M) entries of this manual.
[EIO] I/O error - some physical I/O error. This error may in some cases occur on a call following the one to which it actually
[EISCONN] Socket is already connected. A request was made on an already connected socket, or, a or request on a connected socket
specified a destination other than the connected party.
[EISDIR] Is a directory. An attempt to open a directory for writing.
[ELOOP] Too many levels of symbolic links were encountered while resolving a path name. See fs_symlinks(5) for more information.
[EMFILE] Too many open files. No process may have more than a system-defined number of file descriptors open at a time.
[EMLINK] Too many links. An attempt to make more than the maximum number of links to a file.
[EMSGSIZE] Message too long. The socket requires that the message be sent atomically, and the size of the message to be sent made this
[ENAMETOOLONG] File name too long. A path specified exceeds the maximum path length for the system. The maximum path length is specified
by and is defined in PATH_MAX is guaranteed to be at least 1023 bytes. This error is also generated if the length of a path
name component exceeds and the option is in effect for the specified path. Currently, is in effect only for HFS file sys-
tems configured to allow path name components up to 255 bytes long (see convertfs(1M)) and therefore only path names refer-
ring to such file systems can generate the error for this case. The values of and for a particular path name can be queried
by using the system call (see pathconf(2)).
[ENETDOWN] Network is down. A socket operation encountered a dead network.
[ENETRESET] Network dropped connection on reset. The host you were connected to crashed and rebooted.
[ENETUNREACH] Network is unreachable. A socket operation was attempted to an unreachable network.
[ENFILE] File table overflow. The system's table of open files is full, and temporarily no more can be accepted.
[ENOBUFS] No buffer space available. An operation on a socket was not performed because the system lacked sufficient buffer space.
[ENODEV] No such device. An attempt was made to apply an inappropriate system call to a device (such as read a write-only device).
[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 path name does not exist. It also occurs with and when key does not refer to any object and the
flag is not set.
[ENOEXEC] Exec format error. A request is made to execute a file which, although it has the appropriate permissions, does not start
with a valid magic number (see a.out(4)), or the file is too small to have a valid executable file header.
[ENOLCK] System lock table is full. Too many files have file locks on them, or there are too many record locks on files, or there
are too many instances of a reading or writing process sleeping until an enforcement mode lock clears. This error may also
indicate system problems in handling a lock request on a remote NFS file. This error is also currently returned for all
attempts to perform locking operations on a remote NFS file that has its locking enforcement mode bit set, since the state-
less nature of NFS prevents maintaining the necessary lock information.
[ENOLINK] No connection. The link with the device has been severed or disconnected.
[ENOMEM] Not enough space. During a system call such as or a program asks for more space than the system is able to supply. This
may not be a temporary condition; the maximum space size is a system parameter. The error can also occur if there is not
enough swap space during a
[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; see msgop(2).
[ENOPROTOOPT] Protocol option not available. This may be returned for a or call (see getsockopt(2)) if the user specified an option that
the local system does not support or for any system call that causes the local system to send a network protocol option that
a remote system does not support, including a system call that operates on an NFS file.
[ENOSPC] No space left on device. During a to an ordinary file, there is no free space left on the device; or no space in system ta-
ble during or while flag is set.
[ENOSYM] Symbol does not exist in executable. The dynamic loader was unable to resolve a symbolic reference in a shared library dur-
ing a call to one of the dynamic loader interface routines (see shl_load(3X). The program may be in an inconsistent state
and should be terminated immediately.
[ENOSYS] Function is not available. The requested function or operation is not implemented or not configured in the system.
[ENOTBLK] Block device required. A nonblock file was mentioned where a block device was required, such as in
[ENOTCONN] Socket is not connected. A request to send or receive data was disallowed because the socket was not connected.
[ENOTDIR] Not a directory. A nondirectory was specified where a directory is required, such as in a path prefix or as an argument to
[ENOTEMPTY] Directory not empty. An attempt was made to remove a nonempty directory.
[ENOTSOCK] Socket operation on nonsocket. An operation was attempted on something that is not a socket.
[ENOTTY] Not a typewriter. The command is inappropriate to the selected device type.
[ENXIO] No such device or address. I/O on a special file refers to a subdevice that does not exist, or is beyond the limits of the
device. It can also occur when, for example, a tape drive is not on line or no disk pack is loaded on a drive.
[EOPNOTSUPP] Operation not supported. The requested operation on a socket or NFS file is either invalid or unsupported. For example,
this might occur when an attempt to a connection on a datagram socket fails.
[EPERM] Not owner. Typically, this error indicates an attempt to modify a file in some way forbidden except to its owner or the
superuser, such as to change its mode. It is also returned for attempts by ordinary users to do things for which they need,
but lack, a special privilege.
[EPFNOSUPPORT] Protocol family not supported. The protocol family has not been configured into the system or no implementation for it
exists. The socket is not connected.
[EPIPE] Broken pipe. Data has been written to a pipe for which the other (reading) end has been closed. This most often occurs
when the reading process exits before the writing process. This condition also generates the signal the error is returned
if the signal is ignored.
Protocol not supported. The protocol has not been configured into the system or no implementation for it exists.
[EPROTOTYPE] Protocol wrong type for socket. A protocol was specified that does not support the semantics of the socket type requested.
For example, ARPA Internet UDP protocol cannot be used with type
[ERANGE] Result too large. The value of a function in the math package(3M) is not representable within machine precision, or a call
would cause either a semaphore value or a semaphore adjust value to exceed it system-imposed maximum.
[EROFS] Read-only file system. An attempt to modify a file or directory was made on a device mounted read-only.
[ESHUTDOWN] Cannot send after socket shutdown. A request to send data was disallowed because the socket had already been shut down with
a previous call.
Socket type not supported. The support for the socket type has not been configured into the system or no implementation for
[ESPIPE] Illegal seek. An was issued to a pipe.
[ESRCH] No such process. No process can be found corresponding to that specified by pid in or or the process is not accessible.
[ETIMEDOUT] Connection timed out. A request failed because the connected party did not properly respond after a period of time (timeout
period varies, depending on the communication protocol).
[ETXTBSY] Text file busy. An attempt to execute an executable file which is currently open for writing (or reading). Also, an
attempt to open for writing an otherwise writable file which is currently open for execution.
[EWOULDBLOCK] Operation would block. An operation which would cause a process to block was attempted on an object in nonblocking mode
(see ioctl(2) and fcntl(2)).
[EXDEV] Cross-device link. A link to a file on another device was attempted.
The following NFS errors are also defined:
[EREFUSED] The same error as The external variable is defined as for NFS compatibility.
[EREMOTE] Too many levels of remote in path. An attempt was made to remotely mount an NFS file system into a path which
already has a remotely mounted NFS file system component.
[ESTALE] Stale NFS file handle. A client referenced an open file, but the file was previously deleted.