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
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