Linux errno详解

1. 错误码 / errno

Linux中系统调用的错误都存储于 errno中，errno由操作系统维护，存储就近发生的错误，即下一次的错误码会覆盖掉上一次的错误。

PS: 只有当系统调用或者调用lib函数时出错，才会置位errno！

查看系统中所有的errno所代表的含义，可以采用如下的代码：

/* Function: obtain the errno string

*   char *strerror(int errno)

*/

#include <stdio.h>

#include <string.h>     //for strerror()

//#include <errno.h>

int main()

{

    int tmp = 0;

    for(tmp = 0; tmp <=256; tmp++)

    {

        printf("errno: %2d\t%s\n",tmp,strerror(tmp));

    }

    return 0;

}

输出信息如下：

errno:  0       Success

errno:  1       Operation not permitted

errno:  2       No such file or directory

errno:  3       No such process

errno:  4       Interrupted system call

errno:  5       Input/output error

errno:  6       No such device or address

errno:  7       Argument list too long

errno:  8       Exec format error

errno:  9       Bad file descriptor

errno: 10       No child processes

errno: 11       Resource temporarily unavailable

errno: 12       Cannot allocate memory

errno: 13       Permission denied

errno: 14       Bad address

errno: 15       Block device required

errno: 16       Device or resource busy

errno: 17       File exists

errno: 18       Invalid cross-device link

errno: 19       No such device

errno: 20       Not a directory

errno: 21       Is a directory

errno: 22       Invalid argument

errno: 23       Too many open files in system

errno: 24       Too many open files

errno: 25       Inappropriate ioctl for device

errno: 26       Text file busy

errno: 27       File too large

errno: 28       No space left on device

errno: 29       Illegal seek

errno: 30       Read-only file system

errno: 31       Too many links

errno: 32       Broken pipe

errno: 33       Numerical argument out of domain

errno: 34       Numerical result out of range

errno: 35       Resource deadlock avoided

errno: 36       File name too long

errno: 37       No locks available

errno: 38       Function not implemented

errno: 39       Directory not empty

errno: 40       Too many levels of symbolic links

errno: 41       Unknown error 41

errno: 42       No message of desired type

errno: 43       Identifier removed

errno: 44       Channel number out of range

errno: 45       Level 2 not synchronized

errno: 46       Level 3 halted

errno: 47       Level 3 reset

errno: 48       Link number out of range

errno: 49       Protocol driver not attached

errno: 50       No CSI structure available

errno: 51       Level 2 halted

errno: 52       Invalid exchange

errno: 53       Invalid request descriptor

errno: 54       Exchange full

errno: 55       No anode

errno: 56       Invalid request code

errno: 57       Invalid slot

errno: 58       Unknown error 58

errno: 59       Bad font file format

errno: 60       Device not a stream

errno: 61       No data available

errno: 62       Timer expired

errno: 63       Out of streams resources

errno: 64       Machine is not on the network

errno: 65       Package not installed

errno: 66       Object is remote

errno: 67       Link has been severed

errno: 68       Advertise error

errno: 69       Srmount error

errno: 70       Communication error on send

errno: 71       Protocol error

errno: 72       Multihop attempted

errno: 73       RFS specific error

errno: 74       Bad message

errno: 75       Value too large for defined data type

errno: 76       Name not unique on network

errno: 77       File descriptor in bad state

errno: 78       Remote address changed

errno: 79       Can not access a needed shared library

errno: 80       Accessing a corrupted shared library

errno: 81       .lib section in a.out corrupted

errno: 82       Attempting to link in too many shared libraries

errno: 83       Cannot exec a shared library directly

errno: 84       Invalid or incomplete multibyte or wide character

errno: 85       Interrupted system call should be restarted

errno: 86       Streams pipe error

errno: 87       Too many users

errno: 88       Socket operation on non-socket

errno: 89       Destination address required

errno: 90       Message too long

errno: 91       Protocol wrong type for socket

errno: 92       Protocol not available

errno: 93       Protocol not supported

errno: 94       Socket type not supported

errno: 95       Operation not supported

errno: 96       Protocol family not supported

errno: 97       Address family not supported by protocol

errno: 98       Address already in use

errno: 99       Cannot assign requested address

errno: 100      Network is down

errno: 101      Network is unreachable

errno: 102      Network dropped connection on reset

errno: 103      Software caused connection abort

errno: 104      Connection reset by peer

errno: 105      No buffer space available

errno: 106      Transport endpoint is already connected

errno: 107      Transport endpoint is not connected

errno: 108      Cannot send after transport endpoint shutdown

errno: 109      Too many references: cannot splice

errno: 110      Connection timed out

errno: 111      Connection refused

errno: 112      Host is down

errno: 113      No route to host

errno: 114      Operation already in progress

errno: 115      Operation now in progress

errno: 116      Stale file handle

errno: 117      Structure needs cleaning

errno: 118      Not a XENIX named type file

errno: 119      No XENIX semaphores available

errno: 120      Is a named type file

errno: 121      Remote I/O error

errno: 122      Disk quota exceeded

errno: 123      No medium found

errno: 124      Wrong medium type

errno: 125      Operation canceled

errno: 126      Required key not available

errno: 127      Key has expired

errno: 128      Key has been revoked

errno: 129      Key was rejected by service

errno: 130      Owner died

errno: 131      State not recoverable

errno: 132      Operation not possible due to RF-kill

errno: 133      Memory page has hardware error

errno: 134~255  unknown error!

Linux中，在头文件 /usr/include/asm-generic/errno-base.h 对基础常用errno进行了宏定义：

#ifndef _ASM_GENERIC_ERRNO_BASE_H

#define _ASM_GENERIC_ERRNO_BASE_H

#define EPERM        1  /* Operation not permitted */

#define ENOENT       2  /* No such file or directory */

#define ESRCH        3  /* No such process */

#define EINTR        4  /* Interrupted system call */

#define EIO      5  /* I/O error */

#define ENXIO        6  /* No such device or address */

#define E2BIG        7  /* Argument list too long */

#define ENOEXEC      8  /* Exec format error */

#define EBADF        9  /* Bad file number */

#define ECHILD      10  /* No child processes */

#define EAGAIN      11  /* Try again */

#define ENOMEM      12  /* Out of memory */

#define EACCES      13  /* Permission denied */

#define EFAULT      14  /* Bad address */

#define ENOTBLK     15  /* Block device required */

#define EBUSY       16  /* Device or resource busy */

#define EEXIST      17  /* File exists */

#define EXDEV       18  /* Cross-device link */

#define ENODEV      19  /* No such device */

#define ENOTDIR     20  /* Not a directory */

#define EISDIR      21  /* Is a directory */

#define EINVAL      22  /* Invalid argument */

#define ENFILE      23  /* File table overflow */

#define EMFILE      24  /* Too many open files */

#define ENOTTY      25  /* Not a typewriter */

#define ETXTBSY     26  /* Text file busy */

#define EFBIG       27  /* File too large */

#define ENOSPC      28  /* No space left on device */

#define ESPIPE      29  /* Illegal seek */

#define EROFS       30  /* Read-only file system */

#define EMLINK      31  /* Too many links */

#define EPIPE       32  /* Broken pipe */

#define EDOM        33  /* Math argument out of domain of func */

#define ERANGE      34  /* Math result not representable */

#endif

在 /usr/include/asm-asm-generic/errno.h 中，对剩余的errno做了宏定义：

#ifndef _ASM_GENERIC_ERRNO_H

#define _ASM_GENERIC_ERRNO_H

#include <asm-generic/errno-base.h>

#define EDEADLK     35  /* Resource deadlock would occur */

#define ENAMETOOLONG    36  /* File name too long */

#define ENOLCK      37  /* No record locks available */

#define ENOSYS      38  /* Function not implemented */

#define ENOTEMPTY   39  /* Directory not empty */

#define ELOOP       40  /* Too many symbolic links encountered */

#define EWOULDBLOCK EAGAIN  /* Operation would block */

#define ENOMSG      42  /* No message of desired type */

#define EIDRM       43  /* Identifier removed */

#define ECHRNG      44  /* Channel number out of range */

#define EL2NSYNC    45  /* Level 2 not synchronized */

#define EL3HLT      46  /* Level 3 halted */

#define EL3RST      47  /* Level 3 reset */

#define ELNRNG      48  /* Link number out of range */

#define EUNATCH     49  /* Protocol driver not attached */

#define ENOCSI      50  /* No CSI structure available */

#define EL2HLT      51  /* Level 2 halted */

#define EBADE       52  /* Invalid exchange */

#define EBADR       53  /* Invalid request descriptor */

#define EXFULL      54  /* Exchange full */

#define ENOANO      55  /* No anode */

#define EBADRQC     56  /* Invalid request code */

#define EBADSLT     57  /* Invalid slot */

#define EDEADLOCK   EDEADLK

#define EBFONT      59  /* Bad font file format */

#define ENOSTR      60  /* Device not a stream */

#define ENODATA     61  /* No data available */

#define ETIME       62  /* Timer expired */

#define ENOSR       63  /* Out of streams resources */

#define ENONET      64  /* Machine is not on the network */

#define ENOPKG      65  /* Package not installed */

#define EREMOTE     66  /* Object is remote */

#define ENOLINK     67  /* Link has been severed */

#define EADV        68  /* Advertise error */

#define ESRMNT      69  /* Srmount error */

#define ECOMM       70  /* Communication error on send */

#define EPROTO      71  /* Protocol error */

#define EMULTIHOP   72  /* Multihop attempted */

#define EDOTDOT     73  /* RFS specific error */

#define EBADMSG     74  /* Not a data message */

#define EOVERFLOW   75  /* Value too large for defined data type */

#define ENOTUNIQ    76  /* Name not unique on network */

#define EBADFD      77  /* File descriptor in bad state */

#define EREMCHG     78  /* Remote address changed */

#define ELIBACC     79  /* Can not access a needed shared library */

#define ELIBBAD     80  /* Accessing a corrupted shared library */

#define ELIBSCN     81  /* .lib section in a.out corrupted */

#define ELIBMAX     82  /* Attempting to link in too many shared libraries */

#define ELIBEXEC    83  /* Cannot exec a shared library directly */

#define EILSEQ      84  /* Illegal byte sequence */

#define ERESTART    85  /* Interrupted system call should be restarted */

#define ESTRPIPE    86  /* Streams pipe error */

#define EUSERS      87  /* Too many users */

#define ENOTSOCK    88  /* Socket operation on non-socket */

#define EDESTADDRREQ    89  /* Destination address required */

#define EMSGSIZE    90  /* Message too long */

#define EPROTOTYPE  91  /* Protocol wrong type for socket */

#define ENOPROTOOPT 92  /* Protocol not available */

#define EPROTONOSUPPORT 93  /* Protocol not supported */

#define ESOCKTNOSUPPORT 94  /* Socket type not supported */

#define EOPNOTSUPP  95  /* Operation not supported on transport endpoint */

#define EPFNOSUPPORT    96  /* Protocol family not supported */

#define EAFNOSUPPORT    97  /* Address family not supported by protocol */

#define EADDRINUSE  98  /* Address already in use */

#define EADDRNOTAVAIL   99  /* Cannot assign requested address */

#define ENETDOWN    100 /* Network is down */

#define ENETUNREACH 101 /* Network is unreachable */

#define ENETRESET   102 /* Network dropped connection because of reset */

#define ECONNABORTED    103 /* Software caused connection abort */

#define ECONNRESET  104 /* Connection reset by peer */

#define ENOBUFS     105 /* No buffer space available */

#define EISCONN     106 /* Transport endpoint is already connected */

#define ENOTCONN    107 /* Transport endpoint is not connected */

#define ESHUTDOWN   108 /* Cannot send after transport endpoint shutdown */

#define ETOOMANYREFS    109 /* Too many references: cannot splice */

#define ETIMEDOUT   110 /* Connection timed out */

#define ECONNREFUSED    111 /* Connection refused */

#define EHOSTDOWN   112 /* Host is down */

#define EHOSTUNREACH    113 /* No route to host */

#define EALREADY    114 /* Operation already in progress */

#define EINPROGRESS 115 /* Operation now in progress */

#define ESTALE      116 /* Stale file handle */

#define EUCLEAN     117 /* Structure needs cleaning */

#define ENOTNAM     118 /* Not a XENIX named type file */

#define ENAVAIL     119 /* No XENIX semaphores available */

#define EISNAM      120 /* Is a named type file */

#define EREMOTEIO   121 /* Remote I/O error */

#define EDQUOT      122 /* Quota exceeded */

#define ENOMEDIUM   123 /* No medium found */

#define EMEDIUMTYPE 124 /* Wrong medium type */

#define ECANCELED   125 /* Operation Canceled */

#define ENOKEY      126 /* Required key not available */

#define EKEYEXPIRED 127 /* Key has expired */

#define EKEYREVOKED 128 /* Key has been revoked */

#define EKEYREJECTED    129 /* Key was rejected by service */

/* for robust mutexes */

#define EOWNERDEAD  130 /* Owner died */

#define ENOTRECOVERABLE 131 /* State not recoverable */

#define ERFKILL     132 /* Operation not possible due to RF-kill */

#define EHWPOISON   133 /* Memory page has hardware error */

#endif

2. 打印错误信息

1). 打印错误信息 / perror

作用：

打印系统错误信息
头文件：
#include <stdio.h>
函数原型：
void perror(const char *s)
参数：
s: 字符串提示符

输出形式：

const char *s: strerror(errno) //提示符：发生系统错误的原因

返回值：

无返回值

2). 字符串显示错误信息 / strerror

作用：

将错误码以字符串的信息显示出来
头文件：
#include <string.h>
函数原型：
char *strerror(int errnum);
参数：
errnum: 即errno

返回值：

返回错误码字符串信息

巴特西

Linux errno详解

1. 错误码 / errno

2. 打印错误信息

1). 打印错误信息 / perror

2). 字符串显示错误信息 / strerror

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