1. 錯誤碼 / errno
Linux中系統調用的錯誤都存儲於 errno中，errno由操作系統維護，存儲就近發生的錯誤，即下一次的錯誤碼會覆蓋掉上一次的錯誤。
PS: 只有當系統調用或者調用lib函數時出錯，纔會置位
errno！
查看系統中所有的errno所代表的含義，可以採用如下的代碼：
/* Function: obtain the errno string
* char *strerror(int errno)
*/
//#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;
}
輸出信息如下：
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，在頭文件 /usr/include/asm-generic/errno-base.h 對基礎常用errno進行了宏定義：
#ifndef _ASM_GENERIC_ERRNO_BASE_H
#define _ASM_GENERIC_ERRNO_BASE_H
在 /usr/include/asm-asm-generic/errno.h 中，對剩餘的errno做了宏定義：
#ifndef _ASM_GENERIC_ERRNO_H
#define _ASM_GENERIC_ERRNO_H
/* for robust mutexes /
2. 打印錯誤信息
1). 打印錯誤信息 / perror
- 作用：
打印系統錯誤信息頭文件：
#include <stdio.h>函數原型：
void perror(const char *s)參數：
s: 字符串提示符
- 輸出形式：
const char *s: strerror(errno) //提示符：發生系統錯誤的原因返回值：
無返回值
2). 字符串顯示錯誤信息 / strerror
- 作用：
將錯誤碼以字符串的信息顯示出來頭文件：
#include <string.h>函數原型：
char *strerror(int errnum);參數：
errnum: 即errno
- 返回值：
返回錯誤碼字符串信息