在程序出错时，我们通过全局变量错误号errno和perror函数能够很快的定位到错误原因。
Linux错误代码及其含义
C Name Value Description 含义
Success 0 Success 成功
EPERM 1 Operation not permitted 操作不允许
ENOENT 2 No such file or directory 没有这样的文件或目录
ESRCH 3 No such process 没有这样的过程
EINTR 4 Interrupted system call 系统调用被中断
EIO 5 I/O error I/O错误
ENXIO 6 No such device or address 没有这样的设备或地址
E2BIG 7 Arg list too long 参数列表太长
ENOEXEC 8 Exec format error 执行格式错误
EBADF 9 Bad file number 坏的文件描述符
ECHILD 10 No child processes 没有子进程
EAGAIN 11 Try again 资源暂时不可用
ENOMEM 12 Out of memory 内存溢出
EACCES 13 Permission denied 拒绝许可
EFAULT 14 Bad address 错误的地址
ENOTBLK 15 Block device required 块设备请求
EBUSY 16 Device or resource busy 设备或资源忙
EEXIST 17 File exists 文件存在
EXDEV 18 Cross-device link 无效的交叉链接
ENODEV 19 No such device 设备不存在
ENOTDIR 20 Not a directory 不是一个目录
EISDIR 21 Is a directory 是一个目录
EINVAL 22 Invalid argument 无效的参数
ENFILE* 23 File table overflow 打开太多的文件系统
EMFILE 24 Too many open files 打开的文件过多
ENOTTY 25 Not a tty device 不是tty设备
ETXTBSY 26 Text file busy 文本文件忙
EFBIG 27 File too large 文件太大
ENOSPC 28 No space left on device 设备上没有空间
ESPIPE 29 Illegal seek 非法移位
EROFS 30 Read-only file system 只读文件系统
EMLINK 31 Too many links 太多的链接
EPIPE 32 Broken pipe 管道破裂
EDOM 33 Math argument out of domain 数值结果超出范围
ERANGE 34 Math result not representable 数值结果不具代表性
EDEADLK 35 Resource deadlock would occur 资源死锁错误
ENAMETOOLONG 36 Filename too long 文件名太长
ENOLCK 37 No record locks available 没有可用锁
ENOSYS 38 Function not implemented 功能没有实现
ENOTEMPTY 39 Directory not empty 目录不空
ELOOP 40 Too many symbolic links encountered 符号链接层次太多
EWOULDBLOCK 41 Same as EAGAIN 和EAGAIN一样
ENOMSG 42 No message of desired type 没有期望类型的消息
EIDRM 43 Identifier removed 标识符删除
ECHRNG 44 Channel number out of range 频道数目超出范围
EL2NSYNC 45 Level 2 not synchronized 2级不同步
EL3HLT 46 Level 3 halted 3级中断
EL3RST 47 Level 3 reset 3级复位
ELNRNG 48 Link number out of range 链接数超出范围
EUNATCH 49 Protocol driver not attached 协议驱动程序没有连接
ENOCSI 50 No CSI structure available 没有可用CSI结构
EL2HLT 51 Level 2 halted 2级中断
EBADE 52 Invalid exchange 无效的交换
EBADR 53 Invalid request descriptor 请求描述符无效
EXFULL 54 Exchange full 交换全
ENOANO 55 No anode 没有阳极
EBADRQC 56 Invalid request code 无效的请求代码
EBADSLT 57 Invalid slot 无效的槽
EDEADLOCK 58 Same as EDEADLK 和EDEADLK一样
EBFONT 59 Bad font file format 错误的字体文件格式
ENOSTR 60 Device not a stream 设备不是字符流
ENODATA 61 No data available 无可用数据
ETIME 62 Timer expired 计时器过期
ENOSR 63 Out of streams resources 流资源溢出
ENONET 64 Machine is not on the network 机器不上网
ENOPKG 65 Package not installed 没有安装软件包
EREMOTE 66 Object is remote 对象是远程的
ENOLINK 67 Link has been severed 联系被切断
EADV 68 Advertise error 广告的错误
ESRMNT 69 Srmount error srmount错误
ECOMM 70 Communication error on send 发送时的通讯错误
EPROTO 71 Protocol error 协议错误
EMULTIHOP 72 Multihop attempted 多跳尝试
EDOTDOT 73 RFS specific error RFS特定的错误
EBADMSG 74 Not a data message 非数据消息
EOVERFLOW 75 Value too large for defined data type 值太大,对于定义数据类型
ENOTUNIQ 76 Name not unique on network 名不是唯一的网络
EBADFD 77 File descriptor in bad state 文件描述符在坏状态
EREMCHG 78 Remote address changed 远程地址改变了
ELIBACC 79 Cannot access a needed shared library 无法访问必要的共享库
ELIBBAD 80 Accessing a corrupted shared library 访问损坏的共享库
ELIBSCN 81 A .lib section in an .out is corrupted 库段. out损坏
ELIBMAX 82 Linking in too many shared libraries 试图链接太多的共享库
ELIBEXEC 83 Cannot exec a shared library directly 不能直接执行一个共享库
EILSEQ 84 Illegal byte sequence 无效的或不完整的多字节或宽字符
ERESTART 85 Interrupted system call should be restarted 应该重新启动中断的系统调用
ESTRPIPE 86 Streams pipe error 流管错误
EUSERS 87 Too many users 用户太多
ENOTSOCK 88 Socket operation on non-socket 套接字操作在非套接字上
EDESTADDRREQ 89 Destination address required 需要目标地址
EMSGSIZE 90 Message too long 消息太长
EPROTOTYPE 91 Protocol wrong type for socket socket协议类型错误
ENOPROTOOPT 92 Protocol not available 协议不可用
EPROTONOSUPPORT 93 Protocol not supported 不支持的协议
ESOCKTNOSUPPORT 94 Socket type not supported 套接字类型不受支持
EOPNOTSUPP 95 Operation not supported on transport 不支持的操作
EPFNOSUPPORT 96 Protocol family not supported 不支持的协议族
EAFNOSUPPORT 97 Address family not supported by protocol 协议不支持的地址
EADDRINUSE 98 Address already in use 地址已在使用
EADDRNOTAVAIL 99 Cannot assign requested address 无法分配请求的地址
ENETDOWN 100 Network is down 网络瘫痪
ENETUNREACH 101 Network is unreachable 网络不可达
ENETRESET 102 Network dropped 网络连接丢失
ECONNABORTED 103 Software caused connection 软件导致连接中断
ECONNRESET 104 Connection reset by 连接被重置
ENOBUFS 105 No buffer space available 没有可用的缓冲空间
EISCONN 106 Transport endpoint 传输端点已经连接
ENOTCONN 107 Transport endpoint 传输终点没有连接
ESHUTDOWN 108 Cannot send after transport 传输后无法发送
ETOOMANYREFS 109 Too many references 太多的参考
ETIMEDOUT 110 Connection timed 连接超时
ECONNREFUSED 111 Connection refused 拒绝连接
EHOSTDOWN 112 Host is down 主机已关闭
EHOSTUNREACH 113 No route to host 没有主机的路由
EALREADY 114 Operation already 已运行
EINPROGRESS 115 Operation now in 正在运行
ESTALE 116 Stale NFS file handle 陈旧的NFS文件句柄
EUCLEAN 117 Structure needs cleaning 结构需要清洗
ENOTNAM 118 Not a XENIX-named 不是XENIX命名的
ENAVAIL 119 No XENIX semaphores 没有XENIX信号量
EISNAM 120 Is a named type file 是一个命名的文件类型
EREMOTEIO 121 Remote I/O error 远程输入/输出错误
EDQUOT 122 Quota exceeded 超出磁盘配额
ENOMEDIUM 123 No medium found 没有磁盘被发现
EMEDIUMTYPE 124 Wrong medium type 错误的媒体类型
ECANCELED 125 Operation Canceled 取消操作
ENOKEY 126 Required key not available 所需键不可用
EKEYEXPIRED 127 Key has expired 关键已过期
EKEYREVOKED 128 Key has been revoked 关键被撤销
EKEYREJECTED 129 Key was rejected by service 关键被拒绝服务
EOWNERDEAD 130 Owner died 所有者死亡
ENOTRECOVERABLE 131 State not recoverable 状态不可恢复
ERFKILL 132 Operation not possible due to RF-kill 由于RF-kill而无法操作
暂时记录这么多，133-255全是Unknown error
二、错误处理函数
许多不同的函数库都在失败时设置全局变量errno的值来指明失败原因。值得注意的是函数报告出错后必须立刻检查errno变量，因为它有可能被下一个函数调用所覆盖。
有两个非常有用的函数可以用来报告出现的错误：
#include <string.>
char *strerror(int errnum);
该函数把错误代码映射为一个字符串，对错误类型进行说明。
#include <stdio.h>
void perror(const char *s);
该函数也把errno变量中报告的错误应为到一个字符串，并把它输出到标准错误输出流。
---------------------
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。
1-34号错误号是在内核源码的include/asm-generic/errno-base.h定义
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
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