错误号

定义于 <cerrno> 的每个宏均展开成 int 类型的整数常量表达式，每个都拥有正值，匹配 POSIX 错误码中的大多数。下列常量得到定义（实现可以定义更多，只要它们以 'E' 开始，后随数字或大写字母）

在标头 `<cerrno>` 定义
E2BIG (C++11)	参数列表过长 (宏常量)
EACCES (C++11)	权限被禁止 (宏常量)
EADDRINUSE (C++11)	地址在使用中 (宏常量)
EADDRNOTAVAIL (C++11)	地址不可用 (宏常量)
EAFNOSUPPORT (C++11)	不支持地址系列 (宏常量)
EAGAIN (C++11)	资源不可用，须重试 (宏常量)
EALREADY (C++11)	连接已在进行 (宏常量)
EBADF (C++11)	坏的的文件描述符 (宏常量)
EBADMSG (C++11)	坏的消息 (宏常量)
EBUSY (C++11)	设备或资源忙 (宏常量)
ECANCELED (C++11)	操作取消 (宏常量)
ECHILD (C++11)	无子进程 (宏常量)
ECONNABORTED (C++11)	连接被打断 (宏常量)
ECONNREFUSED (C++11)	连接被拒绝 (宏常量)
ECONNRESET (C++11)	连接被重置 (宏常量)
EDEADLK (C++11)	资源死锁会发生 (宏常量)
EDESTADDRREQ (C++11)	要求目标地址 (宏常量)
EDOM	数学参数在函数定义域外 (宏常量)
EEXIST (C++11)	文件已存在 (宏常量)
EFAULT (C++11)	坏的地址 (宏常量)
EFBIG (C++11)	文件过大 (宏常量)
EHOSTUNREACH (C++11)	主机不可抵达 (宏常量)
EIDRM (C++11)	标识符被移除 (宏常量)
EILSEQ (C++11)	非法字节序列 (宏常量)
EINPROGRESS (C++11)	操作已在进行 (宏常量)
EINTR (C++11)	函数被中断 (宏常量)
EINVAL (C++11)	非法参数 (宏常量)
EIO (C++11)	I/O 错误 (宏常量)
EISCONN (C++11)	接头已连接 (宏常量)
EISDIR (C++11)	是目录 (宏常量)
ELOOP (C++11)	符号链接级别过多 (宏常量)
EMFILE (C++11)	文件描述符值过大 (宏常量)
EMLINK (C++11)	链接过多 (宏常量)
EMSGSIZE (C++11)	消息过大 (宏常量)
ENAMETOOLONG (C++11)	文件名过长 (宏常量)
ENETDOWN (C++11)	网络不工作 (宏常量)
ENETRESET (C++11)	连接被网络打断 (宏常量)
ENETUNREACH (C++11)	网络不可抵达 (宏常量)
ENFILE (C++11)	系统中打开文件过多 (宏常量)
ENOBUFS (C++11)	无缓冲空间可用 (宏常量)
ENODATA (C++11)	流头已读取队列中无消息 (宏常量)
ENODEV (C++11)	无此设备 (宏常量)
ENOENT (C++11)	无此文件或目录 (宏常量)
ENOEXEC (C++11)	可执行文件格式错误 (宏常量)
ENOLCK (C++11)	无可用锁 (宏常量)
ENOLINK (C++11)	链接已切断 (宏常量)
ENOMEM (C++11)	空间不足 (宏常量)
ENOMSG (C++11)	无所需类型消息 (宏常量)
ENOPROTOOPT (C++11)	协议不可用 (宏常量)
ENOSPC (C++11)	设备无剩余空间 (宏常量)
ENOSR (C++11)	无流资源 (宏常量)
ENOSTR (C++11)	非流 (宏常量)
ENOSYS (C++11)	不支持的函数 (宏常量)
ENOTCONN (C++11)	未连接的接头 (宏常量)
ENOTDIR (C++11)	非目录 (宏常量)
ENOTEMPTY (C++11)	目录非空 (宏常量)
ENOTRECOVERABLE (C++11)	状态不可恢复 (宏常量)
ENOTSOCK (C++11)	非接头 (宏常量)
ENOTSUP (C++11)	不支持 (宏常量)
ENOTTY (C++11)	不适合的 I/O 控制操作 (宏常量)
ENXIO (C++11)	无此设备或地址 (宏常量)
EOPNOTSUPP (C++11)	接头上不支持的操作 (宏常量)
EOVERFLOW (C++11)	值过大而无法存入数据类型 (宏常量)
EOWNERDEAD (C++11)	先前拥有者已死 (宏常量)
EPERM (C++11)	操作不允许 (宏常量)
EPIPE (C++11)	管道损坏 (宏常量)
EPROTO (C++11)	协议错误 (宏常量)
EPROTONOSUPPORT (C++11)	不支持的协议 (宏常量)
EPROTOTYPE (C++11)	接头类型错误的协议 (宏常量)
ERANGE	结果过大 (宏常量)
EROFS (C++11)	只读文件系统 (宏常量)
ESPIPE (C++11)	非法寻位 (宏常量)
ESRCH (C++11)	无此进程 (宏常量)
ETIME (C++11)	流 ioctl() 超时 (宏常量)
ETIMEDOUT (C++11)	连接超时 (宏常量)
ETXTBSY (C++11)	文本文件忙 (宏常量)
EWOULDBLOCK (C++11)	操作会阻塞 (宏常量)
EXDEV (C++11)	跨设备链接 (宏常量)

要求所有值均为唯一值，但 EOPNOTSUPP 与 ENOTSUP 的值可以相同，且 EAGAIN 与 EWOULDBLOCK 的值可以相同。

示例

#include <cerrno>
#include <cstring>
#include <iomanip>
#include <iostream>
 
#define SHOW(x) std::cout << std::setw(15) << #x << ": " << std::strerror(x) << '\n'
 
int main()
{
    std::cout << "Known error codes/messages:\n\n";
 
    SHOW( E2BIG );
    SHOW( EACCES );
    SHOW( EADDRINUSE );
    SHOW( EADDRNOTAVAIL );
    SHOW( EAFNOSUPPORT );
    SHOW( EAGAIN );
    SHOW( EALREADY );
    SHOW( EBADF );
    SHOW( EBADMSG );
    SHOW( EBUSY );
    SHOW( ECANCELED );
    SHOW( ECHILD );
    SHOW( ECONNABORTED );
    SHOW( ECONNREFUSED );
    SHOW( ECONNRESET );
    SHOW( EDEADLK );
    SHOW( EDESTADDRREQ );
    SHOW( EDOM );
    SHOW( EEXIST );
    SHOW( EFAULT );
    SHOW( EFBIG );
    SHOW( EHOSTUNREACH );
    SHOW( EIDRM );
    SHOW( EILSEQ );
    SHOW( EINPROGRESS );
    SHOW( EINTR );
    SHOW( EINVAL );
    SHOW( EIO );
    SHOW( EISCONN );
    SHOW( EISDIR );
    SHOW( ELOOP );
    SHOW( EMFILE );
    SHOW( EMLINK );
    SHOW( EMSGSIZE );
    SHOW( ENAMETOOLONG );
    SHOW( ENETDOWN );
    SHOW( ENETRESET );
    SHOW( ENETUNREACH );
    SHOW( ENFILE );
    SHOW( ENOBUFS );
    SHOW( ENODATA );
    SHOW( ENODEV );
    SHOW( ENOENT );
    SHOW( ENOEXEC );
    SHOW( ENOLCK );
    SHOW( ENOLINK );
    SHOW( ENOMEM );
    SHOW( ENOMSG );
    SHOW( ENOPROTOOPT );
    SHOW( ENOSPC );
    SHOW( ENOSR );
    SHOW( ENOSTR );
    SHOW( ENOSYS );
    SHOW( ENOTCONN );
    SHOW( ENOTDIR );
    SHOW( ENOTEMPTY );
    SHOW( ENOTRECOVERABLE );
    SHOW( ENOTSOCK );
    SHOW( ENOTSUP );
    SHOW( ENOTTY );
    SHOW( ENXIO );
    SHOW( EOPNOTSUPP );
    SHOW( EOVERFLOW );
    SHOW( EOWNERDEAD );
    SHOW( EPERM );
    SHOW( EPIPE );
    SHOW( EPROTO );
    SHOW( EPROTONOSUPPORT );
    SHOW( EPROTOTYPE );
    SHOW( ERANGE );
    SHOW( EROFS );
    SHOW( ESPIPE );
    SHOW( ESRCH );
    SHOW( ETIME );
    SHOW( ETIMEDOUT );
    SHOW( ETXTBSY );
    SHOW( EWOULDBLOCK );
    SHOW( EXDEV );
}

可能的输出：

Known error codes/messages:
 
          E2BIG: Argument list too long
         EACCES: Permission denied
     EADDRINUSE: Address already in use
  EADDRNOTAVAIL: Cannot assign requested address
   EAFNOSUPPORT: Address family not supported by protocol
         EAGAIN: Resource temporarily unavailable
       EALREADY: Operation already in progress
          EBADF: Bad file descriptor
        EBADMSG: Bad message
          EBUSY: Device or resource busy
      ECANCELED: Operation canceled
         ECHILD: No child processes
   ECONNABORTED: Software caused connection abort
   ECONNREFUSED: Connection refused
     ECONNRESET: Connection reset by peer
        EDEADLK: Resource deadlock avoided
   EDESTADDRREQ: Destination address required
           EDOM: Numerical argument out of domain
         EEXIST: File exists
         EFAULT: Bad address
          EFBIG: File too large
   EHOSTUNREACH: No route to host
          EIDRM: Identifier removed
         EILSEQ: Invalid or incomplete multibyte or wide character
    EINPROGRESS: Operation now in progress
          EINTR: Interrupted system call
         EINVAL: Invalid argument
            EIO: Input/output error
        EISCONN: Transport endpoint is already connected
         EISDIR: Is a directory
          ELOOP: Too many levels of symbolic links
         EMFILE: Too many open files
         EMLINK: Too many links
       EMSGSIZE: Message too long
   ENAMETOOLONG: File name too long
       ENETDOWN: Network is down
      ENETRESET: Network dropped connection on reset
    ENETUNREACH: Network is unreachable
         ENFILE: Too many open files in system
        ENOBUFS: No buffer space available
        ENODATA: No data available
         ENODEV: No such device
         ENOENT: No such file or directory
        ENOEXEC: Exec format error
         ENOLCK: No locks available
        ENOLINK: Link has been severed
         ENOMEM: Cannot allocate memory
         ENOMSG: No message of desired type
    ENOPROTOOPT: Protocol not available
         ENOSPC: No space left on device
          ENOSR: Out of streams resources
         ENOSTR: Device not a stream
         ENOSYS: Function not implemented
       ENOTCONN: Transport endpoint is not connected
        ENOTDIR: Not a directory
      ENOTEMPTY: Directory not empty
ENOTRECOVERABLE: State not recoverable
       ENOTSOCK: Socket operation on non-socket
        ENOTSUP: Operation not supported
         ENOTTY: Inappropriate ioctl for device
          ENXIO: No such device or address
     EOPNOTSUPP: Operation not supported
      EOVERFLOW: Value too large for defined data type
     EOWNERDEAD: Owner died
          EPERM: Operation not permitted
          EPIPE: Broken pipe
         EPROTO: Protocol error
EPROTONOSUPPORT: Protocol not supported
     EPROTOTYPE: Protocol wrong type for socket
         ERANGE: Numerical result out of range
          EROFS: Read-only file system
         ESPIPE: Illegal seek
          ESRCH: No such process
          ETIME: Timer expired
      ETIMEDOUT: Connection timed out
        ETXTBSY: Text file busy
    EWOULDBLOCK: Resource temporarily unavailable
          EXDEV: Invalid cross-device link

参阅

errc (C++11)	列出所有标准 `<cerrno>` 宏常量的 std::error_condition 枚举 (类)
errno	展开成 POSIX 兼容的线程局域错误号变量的宏 (宏变量)
perror	显示对应当前错误的字符串于 stderr (函数)
strerror	返回给定错误码的文本版本 (函数)