查看错误代码errno是调试程序的一个重要方法。当linuc 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。
35-132则是在include/asm-generic/errno.h中定义
剩下还有一些更大的错误号是留给内核级别的，如系统调用等，用户程序一般是看不见的这些号的，Ubuntu9.10中/usr/src/linux-headers-2.6.31-21-generic/include/linux/errno.h
#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
#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 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 ＊/
#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 ＊/
#ifdef __KERNEL__
/＊
＊ These should never be seen by user programs. To return one of ERESTART＊
＊ codes, signal_pending() MUST be set. Note that ptrace can observe these
＊ at syscall exit tracing, but they will never be left for the debugged user
＊ process to see.
＊/
#define ERESTARTSYS 512
#define ERESTARTNOINTR 513
#define ERESTARTNOHAND 514 /＊ restart if no handler.. ＊/
#define ENOIOCTLCMD 515 /＊ No ioctl command ＊/
#define ERESTART_RESTARTBLOCK 516 /＊ restart by calling sys_restart_syscall ＊/
/＊ Defined for the NFSv3 protocol ＊/
#define EBADHANDLE 521 /＊ Illegal NFS file handle ＊/
#define ENOTSYNC 522 /＊ Update synchronization mismatch ＊/
#define EBADCOOKIE 523 /＊ Cookie is stale ＊/
#define ENOTSUPP 524 /＊ Operation is not supported ＊/
#define ETOOSMALL 525 /＊ Buffer or request is too small ＊/
#define ESERVERFAULT 526 /＊ An untranslatable error occurred ＊/
#define EBADTYPE 527 /＊ Type not supported by server ＊/
#define EJUKEBOX 528 /＊ Request initiated, but will not complete before timeout ＊/
#define EIOCBQUEUED 529 /＊ iocb queued, will get completion event ＊/
#define EIOCBRETRY 530 /＊ iocb queued, will trigger a retry ＊/
#endif
