номер последней ошибки (number of last error)
Описание (Description)
The <errno.h> header file defines the integer variable errno,
which is set by system calls and some library functions in the
event of an error to indicate what went wrong.
errno
The value in errno is significant only when the return value of
the call indicated an error (i.e., -1 from most system calls; -1
or NULL from most library functions); a function that succeeds is
allowed to change errno. The value of errno is never set to zero
by any system call or library function.
For some system calls and library functions (e.g.,
getpriority(2)), -1 is a valid return on success. In such cases,
a successful return can be distinguished from an error return by
setting errno to zero before the call, and then, if the call
returns a status that indicates that an error may have occurred,
checking to see if errno has a nonzero value.
errno is defined by the ISO C standard to be a modifiable lvalue
of type int, and must not be explicitly declared; errno may be a
macro. errno is thread-local; setting it in one thread does not
affect its value in any other thread.
Error numbers and names
Valid error numbers are all positive numbers. The <errno.h>
header file defines symbolic names for each of the possible error
numbers that may appear in errno.
All the error names specified by POSIX.1 must have distinct
values, with the exception of EAGAIN and EWOULDBLOCK, which may
be the same. On Linux, these two have the same value on all
architectures.
The error numbers that correspond to each symbolic name vary
across UNIX systems, and even across different architectures on
Linux. Therefore, numeric values are not included as part of the
list of error names below. The perror(3) and strerror(3)
functions can be used to convert these names to corresponding
textual error messages.
On any particular Linux system, one can obtain a list of all
symbolic error names and the corresponding error numbers using
the errno(1) command (part of the moreutils package):
$ errno -l
EPERM 1 Operation not permitted
ENOENT 2 No such file or directory
ESRCH 3 No such process
EINTR 4 Interrupted system call
EIO 5 Input/output error
...
The errno(1) command can also be used to look up individual error
numbers and names, and to search for errors using strings from
the error description, as in the following examples:
$ errno 2
ENOENT 2 No such file or directory
$ errno ESRCH
ESRCH 3 No such process
$ errno -s permission
EACCES 13 Permission denied
List of error names
In the list of the symbolic error names below, various names are
marked as follows:
* POSIX.1-2001: The name is defined by POSIX.1-2001, and is
defined in later POSIX.1 versions, unless otherwise indicated.
* POSIX.1-2008: The name is defined in POSIX.1-2008, but was not
present in earlier POSIX.1 standards.
* C99: The name is defined by C99.
Below is a list of the symbolic error names that are defined on
Linux:
E2BIG Argument list too long (POSIX.1-2001).
EACCES Permission denied (POSIX.1-2001).
EADDRINUSE
Address already in use (POSIX.1-2001).
EADDRNOTAVAIL
Address not available (POSIX.1-2001).
EAFNOSUPPORT
Address family not supported (POSIX.1-2001).
EAGAIN Resource temporarily unavailable (may be the same value as
EWOULDBLOCK) (POSIX.1-2001).
EALREADY
Connection already in progress (POSIX.1-2001).
EBADE Invalid exchange.
EBADF Bad file descriptor (POSIX.1-2001).
EBADFD File descriptor in bad state.
EBADMSG
Bad message (POSIX.1-2001).
EBADR Invalid request descriptor.
EBADRQC
Invalid request code.
EBADSLT
Invalid slot.
EBUSY Device or resource busy (POSIX.1-2001).
ECANCELED
Operation canceled (POSIX.1-2001).
ECHILD No child processes (POSIX.1-2001).
ECHRNG Channel number out of range.
ECOMM Communication error on send.
ECONNABORTED
Connection aborted (POSIX.1-2001).
ECONNREFUSED
Connection refused (POSIX.1-2001).
ECONNRESET
Connection reset (POSIX.1-2001).
EDEADLK
Resource deadlock avoided (POSIX.1-2001).
EDEADLOCK
On most architectures, a synonym for EDEADLK. On some
architectures (e.g., Linux MIPS, PowerPC, SPARC), it is a
separate error code "File locking deadlock error".
EDESTADDRREQ
Destination address required (POSIX.1-2001).
EDOM Mathematics argument out of domain of function (POSIX.1,
C99).
EDQUOT Disk quota exceeded (POSIX.1-2001).
EEXIST File exists (POSIX.1-2001).
EFAULT Bad address (POSIX.1-2001).
EFBIG File too large (POSIX.1-2001).
EHOSTDOWN
Host is down.
EHOSTUNREACH
Host is unreachable (POSIX.1-2001).
EHWPOISON
Memory page has hardware error.
EIDRM Identifier removed (POSIX.1-2001).
EILSEQ Invalid or incomplete multibyte or wide character
(POSIX.1, C99).
The text shown here is the glibc error description; in
POSIX.1, this error is described as "Illegal byte
sequence".
EINPROGRESS
Operation in progress (POSIX.1-2001).
EINTR Interrupted function call (POSIX.1-2001); see signal(7).
EINVAL Invalid argument (POSIX.1-2001).
EIO Input/output error (POSIX.1-2001).
EISCONN
Socket is connected (POSIX.1-2001).
EISDIR Is a directory (POSIX.1-2001).
EISNAM Is a named type file.
EKEYEXPIRED
Key has expired.
EKEYREJECTED
Key was rejected by service.
EKEYREVOKED
Key has been revoked.
EL2HLT Level 2 halted.
EL2NSYNC
Level 2 not synchronized.
EL3HLT Level 3 halted.
EL3RST Level 3 reset.
ELIBACC
Cannot access a needed shared library.
ELIBBAD
Accessing a corrupted shared library.
ELIBMAX
Attempting to link in too many shared libraries.
ELIBSCN
.lib section in a.out corrupted
ELIBEXEC
Cannot exec a shared library directly.
ELNRANGE
Link number out of range.
ELOOP Too many levels of symbolic links (POSIX.1-2001).
EMEDIUMTYPE
Wrong medium type.
EMFILE Too many open files (POSIX.1-2001). Commonly caused by
exceeding the RLIMIT_NOFILE resource limit described in
getrlimit(2). Can also be caused by exceeding the limit
specified in /proc/sys/fs/nr_open.
EMLINK Too many links (POSIX.1-2001).
EMSGSIZE
Message too long (POSIX.1-2001).
EMULTIHOP
Multihop attempted (POSIX.1-2001).
ENAMETOOLONG
Filename too long (POSIX.1-2001).
ENETDOWN
Network is down (POSIX.1-2001).
ENETRESET
Connection aborted by network (POSIX.1-2001).
ENETUNREACH
Network unreachable (POSIX.1-2001).
ENFILE Too many open files in system (POSIX.1-2001). On Linux,
this is probably a result of encountering the
/proc/sys/fs/file-max limit (see proc(5)).
ENOANO No anode.
ENOBUFS
No buffer space available (POSIX.1 (XSI STREAMS option)).
ENODATA
The named attribute does not exist, or the process has no
access to this attribute; see xattr(7).
In POSIX.1-2001 (XSI STREAMS option), this error was
described as "No message is available on the STREAM head
read queue".
ENODEV No such device (POSIX.1-2001).
ENOENT No such file or directory (POSIX.1-2001).
Typically, this error results when a specified pathname
does not exist, or one of the components in the directory
prefix of a pathname does not exist, or the specified
pathname is a dangling symbolic link.
ENOEXEC
Exec format error (POSIX.1-2001).
ENOKEY Required key not available.
ENOLCK No locks available (POSIX.1-2001).
ENOLINK
Link has been severed (POSIX.1-2001).
ENOMEDIUM
No medium found.
ENOMEM Not enough space/cannot allocate memory (POSIX.1-2001).
ENOMSG No message of the desired type (POSIX.1-2001).
ENONET Machine is not on the network.
ENOPKG Package not installed.
ENOPROTOOPT
Protocol not available (POSIX.1-2001).
ENOSPC No space left on device (POSIX.1-2001).
ENOSR No STREAM resources (POSIX.1 (XSI STREAMS option)).
ENOSTR Not a STREAM (POSIX.1 (XSI STREAMS option)).
ENOSYS Function not implemented (POSIX.1-2001).
ENOTBLK
Block device required.
ENOTCONN
The socket is not connected (POSIX.1-2001).
ENOTDIR
Not a directory (POSIX.1-2001).
ENOTEMPTY
Directory not empty (POSIX.1-2001).
ENOTRECOVERABLE
State not recoverable (POSIX.1-2008).
ENOTSOCK
Not a socket (POSIX.1-2001).
ENOTSUP
Operation not supported (POSIX.1-2001).
ENOTTY Inappropriate I/O control operation (POSIX.1-2001).
ENOTUNIQ
Name not unique on network.
ENXIO No such device or address (POSIX.1-2001).
EOPNOTSUPP
Operation not supported on socket (POSIX.1-2001).
(ENOTSUP and EOPNOTSUPP have the same value on Linux, but
according to POSIX.1 these error values should be
distinct.)
EOVERFLOW
Value too large to be stored in data type (POSIX.1-2001).
EOWNERDEAD
Owner died (POSIX.1-2008).
EPERM Operation not permitted (POSIX.1-2001).
EPFNOSUPPORT
Protocol family not supported.
EPIPE Broken pipe (POSIX.1-2001).
EPROTO Protocol error (POSIX.1-2001).
EPROTONOSUPPORT
Protocol not supported (POSIX.1-2001).
EPROTOTYPE
Protocol wrong type for socket (POSIX.1-2001).
ERANGE Result too large (POSIX.1, C99).
EREMCHG
Remote address changed.
EREMOTE
Object is remote.
EREMOTEIO
Remote I/O error.
ERESTART
Interrupted system call should be restarted.
ERFKILL
Operation not possible due to RF-kill.
EROFS Read-only filesystem (POSIX.1-2001).
ESHUTDOWN
Cannot send after transport endpoint shutdown.
ESPIPE Invalid seek (POSIX.1-2001).
ESOCKTNOSUPPORT
Socket type not supported.
ESRCH No such process (POSIX.1-2001).
ESTALE Stale file handle (POSIX.1-2001).
This error can occur for NFS and for other filesystems.
ESTRPIPE
Streams pipe error.
ETIME Timer expired (POSIX.1 (XSI STREAMS option)).
(POSIX.1 says "STREAM ioctl(2) timeout".)
ETIMEDOUT
Connection timed out (POSIX.1-2001).
ETOOMANYREFS
Too many references: cannot splice.
ETXTBSY
Text file busy (POSIX.1-2001).
EUCLEAN
Structure needs cleaning.
EUNATCH
Protocol driver not attached.
EUSERS Too many users.
EWOULDBLOCK
Operation would block (may be same value as EAGAIN)
(POSIX.1-2001).
EXDEV Improper link (POSIX.1-2001).
EXFULL Exchange full.
