errno头文件

以前做IO操作时，常常会得到一个errno_t，其实就是整数 typedef int errno_t;

以下是VC的errno头文件，可以看出Error Code定义为一些整数值

 /***
 *errno.h - system wide error numbers (set by system calls)
 *
 *       Copyright (c) Microsoft Corporation. All rights reserved.
 *
 *Purpose:
 *       This file defines the system-wide error numbers (set by
 *       system calls).  Conforms to the XENIX standard.  Extended
 *       for compatibility with Uniforum standard.
 *       [System V]
 *
 *       [Public]
 *
 ****/

 #pragma once

 #ifndef _INC_ERRNO
 #define _INC_ERRNO

 #include

 #ifdef __cplusplus
 extern "C" {
 #endif  /* __cplusplus */

 /* Declare reference to errno */

 #ifndef _CRT_ERRNO_DEFINED
 #define _CRT_ERRNO_DEFINED
 _CRTIMP extern int * __cdecl _errno(void);
 #define errno   (*_errno())

 errno_t __cdecl _set_errno(_In_ int _Value);
 errno_t __cdecl _get_errno(_Out_ int * _Value);
 #endif  /* _CRT_ERRNO_DEFINED */

 /* Error Codes */

 #define EPERM           1
 #define ENOENT          2
 #define ESRCH           3
 #define EINTR           4
 #define EIO             5
 #define ENXIO           6
 #define E2BIG           7
 #define ENOEXEC         8
 #define EBADF           9
 #define ECHILD          10
 #define EAGAIN          11
 #define ENOMEM          12
 #define EACCES          13
 #define EFAULT          14
 #define EBUSY           16
 #define EEXIST          17
 #define EXDEV           18
 #define ENODEV          19
 #define ENOTDIR         20
 #define EISDIR          21
 #define ENFILE          23
 #define EMFILE          24
 #define ENOTTY          25
 #define EFBIG           27
 #define ENOSPC          28
 #define ESPIPE          29
 #define EROFS           30
 #define EMLINK          31
 #define EPIPE           32
 #define EDOM            33
 #define EDEADLK         36
 #define ENAMETOOLONG    38
 #define ENOLCK          39
 #define ENOSYS          40
 #define ENOTEMPTY       41

 /* Error codes used in the Secure CRT functions */

 #ifndef RC_INVOKED
 #if !defined (_SECURECRT_ERRCODE_VALUES_DEFINED)
 #define _SECURECRT_ERRCODE_VALUES_DEFINED
 #define EINVAL          22
 #define ERANGE          34
 #define EILSEQ          42
 #define STRUNCATE       80
 #endif  /* !defined (_SECURECRT_ERRCODE_VALUES_DEFINED) */
 #endif  /* RC_INVOKED */

 /* Support EDEADLOCK for compatibility with older MS-C versions */
 #define EDEADLOCK       EDEADLK

 /* POSIX SUPPLEMENT */
 #define EADDRINUSE      100
 #define EADDRNOTAVAIL   101
 #define EAFNOSUPPORT    102
 #define EALREADY        103
 #define EBADMSG         104
 #define ECANCELED       105
 #define ECONNABORTED    106
 #define ECONNREFUSED    107
 #define ECONNRESET      108
 #define EDESTADDRREQ    109
 #define EHOSTUNREACH    110
 #define EIDRM           111
 #define EINPROGRESS     112
 #define EISCONN         113
 #define ELOOP           114
 #define EMSGSIZE        115
 #define ENETDOWN        116
 #define ENETRESET       117
 #define ENETUNREACH     118
 #define ENOBUFS         119
 #define ENODATA         120
 #define ENOLINK         121
 #define ENOMSG          122
 #define ENOPROTOOPT     123
 #define ENOSR           124
 #define ENOSTR          125
 #define ENOTCONN        126
 #define ENOTRECOVERABLE 127
 #define ENOTSOCK        128
 #define ENOTSUP         129
 #define EOPNOTSUPP      130
 #define EOTHER          131
 #define EOVERFLOW       132
 #define EOWNERDEAD      133
 #define EPROTO          134
 #define EPROTONOSUPPORT 135
 #define EPROTOTYPE      136
 #define ETIME           137
 #define ETIMEDOUT       138
 #define ETXTBSY         139
 #define EWOULDBLOCK     140

 #ifdef __cplusplus
 }
 #endif  /* __cplusplus */

 #endif  /* _INC_ERRNO */

贴在这方便以后查看

但每次对表岂不麻烦，还好好在string.h中已经定义好了通过错误码得到说明的函数 strerror

试试

 #include
 #include

 int main(int argc, char* argv[])
 {

     for (int i = 1; i < 141; i++)
     {
         char* msg = strerror(i);
         printf("%d : %s\n", i, msg);
     }

     getchar();

     return 0;
 }

发现42号之后全是 Unknown error，原因是 errno 中定义之后的是兼容 Older version C的，或者是别的什么，还不清楚。？