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
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
-
输出形式：
const char *s: strerror(errno) //提示符：发生系统错误的原因 -
返回值：返回错误码字符串信息
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