errno（come from baidu）

errno

目录

NAME

errno的一些错误定义

编辑本段NAME

　　errno - number of last error

　　errno 记录系统的最后一次错误代码。代码是一个int型的值，在errno.h中定义

　　if (somecall() == -1) {

　　printf("somecall() failed\n");

　　if (errno == ...) { ... }

　　}

　　这样的例子并不能得到somecall这个函数的运行所产生的错误代码，因为很可能是printf这个函数产生的。

　　if (somecall() == -1) {

　　int errsv = errno;

　　printf("somecall() failed\n");

　　if (errsv == ...) { ... }

　　这样才能真正得到运行somecall函数多带来的错误代码。

　　}

　　 注意： 只有当一个库函数失败时，errno才会被设置。当函数成功运行时，errno的值不会被修改。这意味着我们不能通过测试errno的值来判断是否有错误存在。反之，只有当被调用的函数提示有错误发生时检查errno的值才有意义。

　　查看错误代码errno是调试程序的一个重要方法。当linux C api函数发生异常时,一般会将errno变量(需include errno.h)赋一个整数值,不同的值表示不同的含义,可以通过查看该值推测出错的原因。在实际编程中用这一招解决了不少原本看来莫名其妙的问题。比较 麻烦的是每次都要去linux 源代码 里面查找错误代码的含义，现在把它贴出来，以后需要查时就来这里看了。

编辑本段errno的一些错误定义

　　以下来自linux 2.4.20-18的内核代码中的/usr/include/asm/errno.h

　　#ifndef _I386_ERRNO_H

　　#define _I386_ERRNO_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 /* 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 */

　　#endif