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PROLOG | NAME | SYNOPSIS | DESCRIPTION | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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errno.h(0P) POSIX Programmer's Manual errno.h(0P)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior), or
the interface may not be implemented on Linux.
errno.h — system error numbers
#include <errno.h>
Some of the functionality described on this reference page extends
the ISO C standard. Any conflict between the requirements
described here and the ISO C standard is unintentional. This
volume of POSIX.1‐2017 defers to the ISO C standard.
The ISO C standard only requires the symbols [EDOM], [EILSEQ], and
[ERANGE] to be defined.
The <errno.h> header shall provide a declaration or definition for
errno. The symbol errno shall expand to a modifiable lvalue of
type int. It is unspecified whether errno is a macro or an
identifier declared with external linkage. If a macro definition
is suppressed in order to access an actual object, or a program
defines an identifier with the name errno, the behavior is
undefined.
The <errno.h> header shall define the following macros which shall
expand to integer constant expressions with type int, distinct
positive values (except as noted below), and which shall be
suitable for use in #if preprocessing directives:
E2BIG Argument list too long.
EACCES Permission denied.
EADDRINUSE
Address in use.
EADDRNOTAVAIL
Address not available.
EAFNOSUPPORT
Address family not supported.
EAGAIN Resource unavailable, try again (may be the same value as
[EWOULDBLOCK]).
EALREADY
Connection already in progress.
EBADF Bad file descriptor.
EBADMSG
Bad message.
EBUSY Device or resource busy.
ECANCELED
Operation canceled.
ECHILD No child processes.
ECONNABORTED
Connection aborted.
ECONNREFUSED
Connection refused.
ECONNRESET
Connection reset.
EDEADLK
Resource deadlock would occur.
EDESTADDRREQ
Destination address required.
EDOM Mathematics argument out of domain of function.
EDQUOT Reserved.
EEXIST File exists.
EFAULT Bad address.
EFBIG File too large.
EHOSTUNREACH
Host is unreachable.
EIDRM Identifier removed.
EILSEQ Illegal byte sequence.
EINPROGRESS
Operation in progress.
EINTR Interrupted function.
EINVAL Invalid argument.
EIO I/O error.
EISCONN
Socket is connected.
EISDIR Is a directory.
ELOOP Too many levels of symbolic links.
EMFILE File descriptor value too large.
EMLINK Too many links.
EMSGSIZE
Message too large.
EMULTIHOP
Reserved.
ENAMETOOLONG
Filename too long.
ENETDOWN
Network is down.
ENETRESET
Connection aborted by network.
ENETUNREACH
Network unreachable.
ENFILE Too many files open in system.
ENOBUFS
No buffer space available.
ENODATA
No message is available on the STREAM head read queue.
ENODEV No such device.
ENOENT No such file or directory.
ENOEXEC
Executable file format error.
ENOLCK No locks available.
ENOLINK
Reserved.
ENOMEM Not enough space.
ENOMSG No message of the desired type.
ENOPROTOOPT
Protocol not available.
ENOSPC No space left on device.
ENOSR No STREAM resources.
ENOSTR Not a STREAM.
ENOSYS Functionality not supported.
ENOTCONN
The socket is not connected.
ENOTDIR
Not a directory or a symbolic link to a directory.
ENOTEMPTY
Directory not empty.
ENOTRECOVERABLE
State not recoverable.
ENOTSOCK
Not a socket.
ENOTSUP
Not supported (may be the same value as [EOPNOTSUPP]).
ENOTTY Inappropriate I/O control operation.
ENXIO No such device or address.
EOPNOTSUPP
Operation not supported on socket (may be the same value as
[ENOTSUP]).
EOVERFLOW
Value too large to be stored in data type.
EOWNERDEAD
Previous owner died.
EPERM Operation not permitted.
EPIPE Broken pipe.
EPROTO Protocol error.
EPROTONOSUPPORT
Protocol not supported.
EPROTOTYPE
Protocol wrong type for socket.
ERANGE Result too large.
EROFS Read-only file system.
ESPIPE Invalid seek.
ESRCH No such process.
ESTALE Reserved.
ETIME Stream ioctl() timeout.
ETIMEDOUT
Connection timed out.
ETXTBSY
Text file busy.
EWOULDBLOCK
Operation would block (may be the same value as [EAGAIN]).
EXDEV Cross-device link.
The following sections are informative.
Additional error numbers may be defined on conforming systems; see
the System Interfaces volume of POSIX.1‐2017.
None.
None.
The System Interfaces volume of POSIX.1‐2017, Section 2.3, Error
Numbers
Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The
Open Group Base Specifications Issue 7, 2018 Edition, Copyright
(C) 2018 by the Institute of Electrical and Electronics Engineers,
Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard,
the original IEEE and The Open Group Standard is the referee
document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
Any typographical or formatting errors that appear in this page
are most likely to have been introduced during the conversion of
the source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2017 errno.h(0P)
Pages that refer to this page: signal.h(0p), errno(3p)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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