errno错误码含义及使用

大家好，欢迎来到IT知识分享网。

errno 本质上是一个 int 类型的变量，用于存储错误编号

头文件：

#include <errno.h>

打开一个不存在的文件，测试代码如下：

#include <stdio.h> #include <errno.h> int main ( ) { FILE * pF; pF= fopen ("test.txt","r"); if (pF == NULL) printf ("errno=%d\n",errno); return 0; } gcc errno.c -o errno ./errno errno=2

但你怎麼知道2代表的是什么？，你还得查其错误码的含义

​ #define EPERM 1 /* Operation not permitted */操作不允许 　　#define ENOENT 2 /* No such file or directory */文件/路径不存在 　　#define ESRCH 3 /* No such process */进程不存在 　　#define EINTR 4 /* Interrupted system call */中断的系统调用 　　#define EIO 5 /* I/O error */I/O错误 　　#define ENXIO 6 /* No such device or address */设备/地址不存在 　　#define E2BIG 7 /* Arg list too long */参数列表过长 　　#define ENOEXEC 8 /* Exec format error */执行格式错误 　　#define EBADF 9 /* Bad file number */错误文件编号 　　#define ECHILD 10 /* No child processes */子进程不存在 　　#define EAGAIN 11 /* Try again */重试 　　#define ENOMEM 12 /* Out of memory */内存不足 　　#define EACCES 13 /* Permission denied */无权限 　　#define EFAULT 14 /* Bad address */地址错误 　　#define ENOTBLK 15 /* Block device required */需要块设备 　　#define EBUSY 16 /* Device or resource busy */设备或资源忙 　　#define EEXIST 17 /* File exists */文件已存在 　　#define EXDEV 18 /* Cross-device link */跨设备链路 　　#define ENODEV 19 /* No such device */设备不存在 　　#define ENOTDIR 20 /* Not a directory */路径不存在 　　#define EISDIR 21 /* Is a directory */是路径 　　#define EINVAL 22 /* Invalid argument */无效参数 　　#define ENFILE 23 /* File table overflow */文件表溢出 　　#define EMFILE 24 /* Too many open files */打开的文件过多 　　#define ENOTTY 25 /* Not a typewriter */非打字机 　　#define ETXTBSY 26 /* Text file busy */文本文件忙 　　#define EFBIG 27 /* File too large */文件太大 　　#define ENOSPC 28 /* No space left on device */设备无空间 　　#define ESPIPE 29 /* Illegal seek */非法查询 　　#define EROFS 30 /* Read-only file system */只读文件系统 　　#define EMLINK 31 /* Too many links */链接太多 　　#define EPIPE 32 /* Broken pipe */管道破裂 　　#define EDOM 33 /* Math argument out of domain of func */参数超出函数域 　　#define ERANGE 34 /* Math result not representable */结果无法表示 　　#define EDEADLK 35 /* Resource deadlock would occur */资源将发生死锁 　　#define ENAMETOOLONG 36 /* File name too long */文件名太长 　　#define ENOLCK 37 /* No record locks available */没有可用的记录锁 　　#define ENOSYS 38 /* Function not implemented */函数未实现 　　#define ENOTEMPTY 39 /* Directory not empty */目录非空 　　#define ELOOP 40 /* Too many symbolic links encountered */遇到太多符号链接 　　#define EWOULDBLOCK EAGAIN /* Operation would block */操作会阻塞 　　#define ENOMSG 42 /* No message of desired type */没有符合需求类型的消息 　　#define EIDRM 43 /* Identifier removed */标识符已删除 　　#define ECHRNG 44 /* Channel number out of range */通道编号超出范围 　　#define EL2NSYNC 45 /* Level 2 not synchronized */level2不同步 　　#define EL3HLT 46 /* Level 3 halted */3级停止 　　#define EL3RST 47 /* Level 3 reset */3级重置 　　#define ELNRNG 48 /* Link number out of range */链接编号超出范围 　　#define EUNATCH 49 /* Protocol driver not attached */协议驱动程序没有连接 　　#define ENOCSI 50 /* No CSI structure available */没有可用的CSI结构 　　#define EL2HLT 51 /* Level 2 halted */2级停止 　　#define EBADE 52 /* Invalid exchange */无效交换 　　#define EBADR 53 /* Invalid request descriptor */无效请求描述 　　#define EXFULL 54 /* Exchange full */交换完全 　　#define ENOANO 55 /* No anode */无阳极 　　#define EBADRQC 56 /* Invalid request code */无效请求码 　　#define EBADSLT 57 /* Invalid slot */无效插槽 　　#define EDEADLOCK EDEADLK 　　#define EBFONT 59 /* Bad font file format */错误的字体文件格式 　　#define ENOSTR 60 /* Device not a stream */设备不是流 　　#define ENODATA 61 /* No data available */无数据 　　#define ETIME 62 /* Timer expired */计时器到期 　　#define ENOSR 63 /* Out of streams resources */流资源不足 　　#define ENONET 64 /* Machine is not on the network */机器不在网络上 　　#define ENOPKG 65 /* Package not installed */包未安装 　　#define EREMOTE 66 /* Object is remote */对象是远程 　　#define ENOLINK 67 /* Link has been severed */链接正在服务中 　　#define EADV 68 /* Advertise error */广告错误 　　#define ESRMNT 69 /* Srmount error */？ 　　#define ECOMM 70 /* Communication error on send */发送过程中通讯错误 　　#define EPROTO 71 /* Protocol error */协议错误 　　#define EMULTIHOP 72 /* Multihop attempted */多跳尝试 　　#define EDOTDOT 73 /* RFS specific error */RFS特定错误 　　#define EBADMSG 74 /* Not a data message */不是数据类型消息 　　#define EOVERFLOW 75 /* Value too large for defined data type */对指定的数据类型来说值太大 　　#define ENOTUNIQ 76 /* Name not unique on network */网络上名字不唯一 　　#define EBADFD 77 /* File descriptor in bad state */文件描述符状态错误 　　#define EREMCHG 78 /* Remote address changed */远程地址改变 　　#define ELIBACC 79 /* Can not access a needed shared library */无法访问需要的共享库 　　#define ELIBBAD 80 /* Accessing a corrupted shared library */访问损坏的共享库 　　#define ELIBSCN 81 /* .lib section in a.out corrupted */库部分在a.out损坏 　　#define ELIBMAX 82 /* Attempting to link in too many shared libraries */试图链接太多的共享库 　　#define ELIBEXEC 83 /* Cannot exec a shared library directly */不能直接运行共享库 　　#define EILSEQ 84 /* Illegal byte sequence */非法字节序 　　#define ERESTART 85 /* Interrupted system call should be restarted */应重新启动被中断的系统调用 　　#define ESTRPIPE 86 /* Streams pipe error */流管错误 　　#define EUSERS 87 /* Too many users */用户太多 　　#define ENOTSOCK 88 /* Socket operation on non-socket */在非套接字上进行套接字操作 　　#define EDESTADDRREQ 89 /* Destination address required */需要目的地址 　　#define EMSGSIZE 90 /* Message too long */消息太长 　　#define EPROTOTYPE 91 /* Protocol wrong type for socket */错误协议类型 　　#define ENOPROTOOPT 92 /* Protocol not available */协议不可用 　　#define EPROTONOSUPPORT 93 /* Protocol not supported */不支持协议 　　#define ESOCKTNOSUPPORT 94 /* Socket type not supported */不支持套接字类型 　　#define EOPNOTSUPP 95 /* Operation not supported on transport endpoint */操作上不支持传输端点 　　#define EPFNOSUPPORT 96 /* Protocol family not supported */不支持协议族 　　#define EAFNOSUPPORT 97 /* Address family not supported by protocol */协议不支持地址群 　　#define EADDRINUSE 98 /* Address already in use */地址已被使用 　　#define EADDRNOTAVAIL 99 /* Cannot assign requested address */无法分配请求的地址 　　#define ENETDOWN 100 /* Network is down */网络已关闭 　　#define ENETUNREACH 101 /* Network is unreachable */网络不可达 　　#define ENETRESET 102 /* Network dropped connection because of reset */网络由于复位断开连接 　　#define ECONNABORTED 103 /* Software caused connection abort */软件导致连接终止 　　#define ECONNRESET 104 /* Connection reset by peer */连接被对方复位 　　#define ENOBUFS 105 /* No buffer space available */没有可用的缓存空间 　　#define EISCONN 106 /* Transport endpoint is already connected */传输端点已连接 　　#define ENOTCONN 107 /* Transport endpoint is not connected */传输端点未连接 　　#define ESHUTDOWN 108 /* Cannot send after transport endpoint shutdown */传输端点关闭后不能在发送 　　#define ETOOMANYREFS 109 /* Too many references: cannot splice */太多的引用：无法接合 　　#define ETIMEDOUT 110 /* Connection timed out */连接超时 　　#define ECONNREFUSED 111 /* Connection refused */连接被拒绝 　　#define EHOSTDOWN 112 /* Host is down */主机已关闭 　　#define EHOSTUNREACH 113 /* No route to host */无法路由到主机 　　#define EALREADY 114 /* Operation already in progress */操作已在进程中 　　#define EINPROGRESS 115 /* Operation now in progress */进程中正在进行的操作 　　#define ESTALE 116 /* Stale NFS file handle */旧NFS文件句柄 　　#define EUCLEAN 117 /* Structure needs cleaning */结构需要清理 　　#define ENOTNAM 118 /* Not a XENIX named type file */不是XENIX命名类型文件 　　#define ENAVAIL 119 /* No XENIX semaphores available */没有XENIX信号量可用 　　#define EISNAM 120 /* Is a named type file */是命名类型文件 　　#define EREMOTEIO 121 /* Remote I/O error */远程I/O错误 　　#define EDQUOT 122 /* Quota exceeded */超出配额 　　#define ENOMEDIUM 123 /* No medium found */未找到培养基 　　#define EMEDIUMTYPE 124 /* Wrong medium type */错误的介质类型 ​

但你不觉得太麻烦了吗

方案1：

#include <stdio.h> int main() { FILE *file = fopen("nonexistent_file.txt", "r"); if (file == NULL) { perror("ooo");//若你写perror("Errno");输出为Errno: No such file or directory，变得是冒号前面 return 1; } return 0; } ooo: No such file or directory

void perror(const char *s)

包含头文件#include <stdio.h>

含义：perror ( )用来将上一个函数发生错误的原因输出到标准错误(stderr),参数s 所指的字符串会先打印出,后面再加上错误原因 字符串。此错误原因依照全局变量 errno 的值来决定要输出的字符串。

方案2

int main() { FILE *file = fopen("nonexistent_file.txt", "r"); if (file == NULL) { printf("errno=%s", strerror(errno)); return 1; } return 0; } errno = No such file or directory

char *strerror(int errno) 

 包含头文件                 

#include <errno.h>

#include <string.h>

含义：将错误代码转换为字符串错误信息,可以将该字符串和其它的信息组合输出到用户界面

～每天进步一点点，加油！！