【Linux】Linux系统错误码errno详解

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一、前言

在嵌入式Linux开发中，使用errno进行错误处理是非常常见和必要的。嵌入式系统通常需要处理各种硬件和软件的交互，错误处理和调试是确保系统稳定性和可靠性的关键部分。

errno在嵌入式Linux开发中是一个重要的工具，通过合理使用errno，可以有效地捕获和处理各种错误情况，确保系统的稳定性和可靠性。

二、errno 简介

在Linux系统中，errno是一个全局变量，用于表示最近一次系统调用或库函数调用出错时的错误码。每个错误码对应一个特定的错误类型。了解这些错误码有助于调试和处理错误情况。

要使用errno，需要包含头文件#include

Linux系统调用或库函数在出错时会自动设置errno为相应的错误码。可以在调用函数后检查errno的值来确定错误类型，通过 perror() 或 strerror() 函数将错误码转换为可读的错误消息。针对perror() 和 strerror() 函数的详解，可查看文章《【嵌入式】Linux系统错误码errno详解》。

三、errno 注意事项

1、系统调用或库函数返回后应立即检查errno，因为后续的调用可能会修改errno的值。
2、在多线程环境中，errno通常是线程局部的，每个线程都有自己的errno。这意味着在多线程程序中使用errno是安全的。

四、Linux errno 错误码对照表

在头文件「/usr/include/asm-generic/errno-base.h」中对基础的常用 errno 进行了宏定义：

define	errno	explain
EPERM	1	Operation not permitted
ENOENT	2	No such file or directory
ESRCH	3	No such process
EINTR	4	Interrupted system call
EIO	5	I/O error
ENXIO	6	No such device or address
E2BIG	7	Argument list too long
ENOEXEC	8	Exec format error
EBADF	9	Bad file number
ECHILD	10	No child processes
EAGAIN	11	Try again
ENOMEM	12	Out of memory
EACCES	13	Permission denied
EFAULT	14	Bad address
ENOTBLK	15	Block device required
EBUSY	16	Device or resource busy
EEXIST	17	File exists
EXDEV	18	Cross-device link
ENODEV	19	No such device
ENOTDIR	20	Not a directory
EISDIR	21	Is a directory
EINVAL	22	Invalid argument
ENFILE	23	File table overflow
EMFILE	24	Too many open files
ENOTTY	25	Not a typewriter
ETXTBSY	26	Text file busy
EFBIG	27	File too large
ENOSPC	28	No space left on device
ESPIPE	29	Illegal seek
EROFS	30	Read-only file system
EMLINK	31	Too many links
EPIPE	32	Broken pipe
EDOM	33	Math argument out of domain of func
ERANGE	34	Math result not representable

在 「/usr/include/asm-generic/errno.h」 中，对剩余的 errno 做了宏定义：

define	errno	explain
EDEADLK	35	Resource deadlock would occur
ENAMETOOLONG	36	File name too long
ENOLCK	37	No record locks available
ENOSYS	38	Function not implemented
ENOTEMPTY	39	Directory not empty
ELOOP	40	Too many symbolic links encountered
EWOULDBLOCK	EAGAIN	Operation would block
ENOMSG	42	No message of desired type
EIDRM	43	Identifier removed
ECHRNG	44	Channel number out of range
EL2NSYNC	45	Level 2 not synchronized
EL3HLT	46	Level 3 halted
EL3RST	47	Level 3 reset
ELNRNG	48	Link number out of range
EUNATCH	49	Protocol driver not attached
ENOCSI	50	No CSI structure available
EL2HLT	51	Level 2 halted
EBADE	52	Invalid exchange
EBADR	53	Invalid request descriptor
EXFULL	54	Exchange full
ENOANO	55	No anode
EBADRQC	56	Invalid request code
EBADSLT	57	Invalid slot
EDEADLOCK	EDEADLK
EBFONT	59	Bad font file format
ENOSTR	60	Device not a stream
ENODATA	61	No data available
ETIME	62	Timer expired
ENOSR	63	Out of streams resources
ENONET	64	Machine is not on the network
ENOPKG	65	Package not installed
EREMOTE	66	Object is remote
ENOLINK	67	Link has been severed
EADV	68	Advertise error
ESRMNT	69	Srmount error
ECOMM	70	Communication error on send
EPROTO	71	Protocol error
EMULTIHOP	72	Multihop attempted
EDOTDOT	73	RFS specific error
EBADMSG	74	Not a data message
EOVERFLOW	75	Value too large for defined data type
ENOTUNIQ	76	Name not unique on network
EBADFD	77	File descriptor in bad state
EREMCHG	78	Remote address changed
ELIBACC	79	Can not access a needed shared library
ELIBBAD	80	Accessing a corrupted shared library
ELIBSCN	81	.lib section in a.out corrupted
ELIBMAX	82	Attempting to link in too many shared libraries
ELIBEXEC	83	Cannot exec a shared library directly
EILSEQ	84	Illegal byte sequence
ERESTART	85	Interrupted system call should be restarted
ESTRPIPE	86	Streams pipe error
EUSERS	87	Too many users
ENOTSOCK	88	Socket operation on non-socket
EDESTADDRREQ	89	Destination address required
EMSGSIZE	90	Message too long
EPROTOTYPE	91	Protocol wrong type for socket
ENOPROTOOPT	92	Protocol not available
EPROTONOSUPPORT	93	Protocol not supported
ESOCKTNOSUPPORT	94	Socket type not supported
EOPNOTSUPP	95	Operation not supported on transport endpoint
EPFNOSUPPORT	96	Protocol family not supported
EAFNOSUPPORT	97	Address family not supported by protocol
EADDRINUSE	98	Address already in use
EADDRNOTAVAIL	99	Cannot assign requested address
ENETDOWN	100	Network is down
ENETUNREACH	101	Network is unreachable
ENETRESET	102	Network dropped connection because of reset
ECONNABORTED	103	Software caused connection abort
ECONNRESET	104	Connection reset by peer
ENOBUFS	105	No buffer space available
EISCONN	106	Transport endpoint is already connected
ENOTCONN	107	Transport endpoint is not connected
ESHUTDOWN	108	Cannot send after transport endpoint shutdown
ETOOMANYREFS	109	Too many references: cannot splice
ETIMEDOUT	110	Connection timed out
ECONNREFUSED	111	Connection refused
EHOSTDOWN	112	Host is down
EHOSTUNREACH	113	No route to host
EALREADY	114	Operation already in progress
EINPROGRESS	115	Operation now in progress
ESTALE	116	Stale file handle
EUCLEAN	117	Structure needs cleaning
ENOTNAM	118	Not a XENIX named type file
ENAVAIL	119	No XENIX semaphores available
EISNAM	120	Is a named type file
EREMOTEIO	121	Remote I/O error
EDQUOT	122	Quota exceeded
ENOMEDIUM	123	No medium found
EMEDIUMTYPE	124	Wrong medium type
ECANCELED	125	Operation Canceled
ENOKEY	126	Required key not available
EKEYEXPIRED	127	Key has expired
EKEYREVOKED	128	Key has been revoked
EKEYREJECTED	129	Key was rejected by service
EOWNERDEAD	130	Owner died
ENOTRECOVERABLE	131	State not recoverable
ERFKILL	132	Operation not possible due to RF-kill
EHWPOISON	133	Memory page has hardware error

五、示例

main.c源码

1. #include <stdio.h>
2. #include <string.h>
3. #include <errno.h>
5. int main(int argc, char *argv[])
6. {
7. FILE *file = fopen("./test.txt", "r");
8. if(NULL == file)
9. {
10. printf("fopen err: %s errno = %d\n", strerror(errno), errno);
11. }
12. return 0;
13. }

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