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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
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.1‐2008 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 Function 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.1‐2008.
The System Interfaces volume of POSIX.1‐2008, Section 2.3, Error Numbers
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/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 .