linux下的错误捕获errno和strerror()

        经常在调用linux 系统api 的时候会出现一些错误，比方说使用open() write() creat()之类的函数有些时候会返回-1，也就是调用失败，这个时候往往需要知道失败的原因。这个时候使用errno这个全局变量就相当有用了。

1 errno和strerror()函数

1.1 errno

       在程序代码中包含 #include ，然后每次程序调用失败的时候，系统会自动用用错误代码填充errno这个全局变量，这样你只需要读errno这个全局变量就可以获得失败原因了。

1.2 strerror()函数

        头文件：

        函数原型：char * strerror(int errnum);

        将error编码errnum转换成错误消息，通过字符串返回。

1.3 perror()函数

        头文件：

        函数原型：void perror(const char * msg);

        将错误消息输出到错误输出（stderr），并换行。如果msg为空指针或者指向字符串为空，则向错误输出打印errno对应的错误消息；如果msg不为空，则向错误输出打印msg的内容后再打印冒号、空格和errno对应的错误消息。

2 errno含义

#define ESUC 0 /* Success */
#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 /* Arg 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 */
#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 NFS 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 */

3 在本机打印errno对应错误消息

#include 
#include 
#include 

int main(int argc, char * argv[]) 
{
    for(int i = 0; i < 256; ++i)
    {
        fprintf(stdout, "%s\n", strerror(i));
    }
    return 0;
}

0       Success
1       Operation not permitted
2       No such file or directory
3       No such process
4       Interrupted system call
5       Input/output error
6       No such device or address
7       Argument list too long
8       Exec format error
9       Bad file descriptor
10       No child processes
11       Resource temporarily unavailable
12       Cannot allocate memory
13       Permission denied
14       Bad address
15       Block device required
16       Device or resource busy
17       File exists
18       Invalid cross-device link
19       No such device
20       Not a directory
21       Is a directory
22       Invalid argument
23       Too many open files in system
24       Too many open files
25       Inappropriate ioctl for device
26       Text file busy
27       File too large
28       No space left on device
29       Illegal seek
30       Read-only file system
31       Too many links
32       Broken pipe
33       Numerical argument out of domain
34       Numerical result out of range
35       Resource deadlock avoided
36       File name too long
37       No locks available
38       Function not implemented
39       Directory not empty
40       Too many levels of symbolic links
41       Unknown error 41
42       No message of desired type
43       Identifier removed
44       Channel number out of range
45       Level 2 not synchronized
46       Level 3 halted
47       Level 3 reset
48       Link number out of range
49       Protocol driver not attached
50       No CSI structure available
51       Level 2 halted
52       Invalid exchange
53       Invalid request descriptor
54       Exchange full
55       No anode
56       Invalid request code
57       Invalid slot
58       Unknown error 58
59       Bad font file format
60       Device not a stream
61       No data available
62       Timer expired
63       Out of streams resources
64       Machine is not on the network
65       Package not installed
66       Object is remote
67       Link has been severed
68       Advertise error
69       Srmount error
70       Communication error on send
71       Protocol error
72       Multihop attempted
73       RFS specific error
74       Bad message
75       Value too large for defined data type
76       Name not unique on network
77       File descriptor in bad state
78       Remote address changed
79       Can not access a needed shared library
80       Accessing a corrupted shared library
81       .lib section in a.out corrupted
82       Attempting to link in too many shared libraries
83       Cannot exec a shared library directly
84       Invalid or incomplete multibyte or wide character
85       Interrupted system call should be restarted
86       Streams pipe error
87       Too many users
88       Socket operation on non-socket
89       Destination address required
90       Message too long
91       Protocol wrong type for socket
92       Protocol not available
93       Protocol not supported
94       Socket type not supported
95       Operation not supported
96       Protocol family not supported
97       Address family not supported by protocol
98       Address already in use
99       Cannot assign requested address
100       Network is down
101       Network is unreachable
102       Network dropped connection on reset
103       Software caused connection abort
104       Connection reset by peer
105       No buffer space available
106       Transport endpoint is already connected
107       Transport endpoint is not connected
108       Cannot send after transport endpoint shutdown
109       Too many references: cannot splice
110       Connection timed out
111       Connection refused
112       Host is down
113       No route to host
114       Operation already in progress
115       Operation now in progress
116       Stale NFS file handle
117       Structure needs cleaning
118       Not a XENIX named type file
119       No XENIX semaphores available
120       Is a named type file
121       Remote I/O error
122       Disk quota exceeded
123       No medium found
124       Wrong medium type
125       Operation canceled
126       Unknown error 126