Ubuntu Manpage: This manual page is part of the POSIX Programmer's Manual. The Linux implementation of

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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.

NAME

       errno.h — system error numbers

SYNOPSIS

       #include <errno.h>

DESCRIPTION

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.

APPLICATION USAGE

       Additional  error  numbers may be defined on conforming systems; see the System Interfaces
       volume of POSIX.1‐2008.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

COPYRIGHT

       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 .