31 Linux Error Codes for C Programming Language using errno

131 Linux Error Codes for C Programming Language using errno

Programmers should handle all kinds of errors to protect the program from failure.

In C programming language, there is no direct support for error handling. You have to detect the failure and handle the error. In C programming language, return values represents success or failure. Inside a C program, when a function fails, you should handle the errors accordingly, or at least record the errors in a log file.

When you are running some program on Linux environment, you might notice that it gives some error number. For example, “Error no is : 17″, which doesn’t really say much. You really need to know what error number 17 means.

This article shows all available error numbers along with it descriptions. This article might be a handy reference for you, when you encounter an error number and you would like to know what it means.

• In C programming language, there is an external variable called “errno”.
• From this errno variable you can use some error handling functions to find out the error description and handle it appropriately.
• You have to include errno.h header file to use external variable errno.
• perror function prints error description in standard error.
• The strerror function returns a string describing the error code passed in the argument errnum.

The following C code snippet tries to open a file through open system call. There are two flags in the open call. O_CREAT flag is to create a file, if the file does not exist. O_EXCL flag is used with O_CREAT, if the file is already exist open call will fail with the proper error number.

$ cat fileopen.c
#include <stdio.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
main()
{
// Declaration of a file descriptor
int fd;

// Opening a file
fd = open("/root/sasikala/testing",O_CREAT|O_EXCL);
// If Open is failed
if ( fd < 0 ) {
        printf("Opening file : Failed\n");
        printf ("Error no is : %d\n", errno);
        printf("Error description is : %s\n",strerror(errno));
}
// If Open is success
else
        printf("Opening file : Success\n");

}

$ cc -o fileopen fileopen.c
$ ./fileopen

Opening file : Success

$ ./fileopen
Opening file : Failed
Error no is : 17
Error description is : File exists

At first execution, open got executed successfully, and it created the file since the file was not available. In next execution, it throws an error number 17, which is “File already exist”.

The following table shows list of error numbers and its descriptions in Linux operation system

ERROR CODE TABLE
Error number	Error Code	Error Description
1	EPERM	Operation not permitted
2	ENOENT	No such file or directory
3	ESRCH	No such process
4	EINTR	Interrupted system call
5	EIO	I/O error
6	ENXIO	No such device or address
7	E2BIG	Argument list too long
8	ENOEXEC	Exec format error
9	EBADF	Bad file number
10	ECHILD	No child processes
11	EAGAIN	Try again
12	ENOMEM	Out of memory
13	EACCES	Permission denied
14	EFAULT	Bad address
15	ENOTBLK	Block device required
16	EBUSY	Device or resource busy
17	EEXIST	File exists
18	EXDEV	Cross-device link
19	ENODEV	No such device
20	ENOTDIR	Not a directory
21	EISDIR	Is a directory
22	EINVAL	Invalid argument
23	ENFILE	File table overflow
24	EMFILE	Too many open files
25	ENOTTY	Not a typewriter
26	ETXTBSY	Text file busy
27	EFBIG	File too large
28	ENOSPC	No space left on device
29	ESPIPE	Illegal seek
30	EROFS	Read-only file system
31	EMLINK	Too many links
32	EPIPE	Broken pipe
33	EDOM	Math argument out of domain of func
34	ERANGE	Math result not representable
35	EDEADLK	Resource deadlock would occur
36	ENAMETOOLONG	File name too long
37	ENOLCK	No record locks available
38	ENOSYS	Function not implemented
39	ENOTEMPTY	Directory not empty
40	ELOOP	Too many symbolic links encountered
42	ENOMSG	No message of desired type
43	EIDRM	Identifier removed
44	ECHRNG	Channel number out of range
45	EL2NSYNC	Level 2 not synchronized
46	EL3HLT	Level 3 halted
47	EL3RST	Level 3 reset
48	ELNRNG	Link number out of range
49	EUNATCH	Protocol driver not attached
50	ENOCSI	No CSI structure available
51	EL2HLT	Level 2 halted
52	EBADE	Invalid exchange
53	EBADR	Invalid request descriptor
54	EXFULL	Exchange full
55	ENOANO	No anode
56	EBADRQC	Invalid request code
57	EBADSLT	Invalid slot
59	EBFONT	Bad font file format
60	ENOSTR	Device not a stream
61	ENODATA	No data available
62	ETIME	Timer expired
63	ENOSR	Out of streams resources
64	ENONET	Machine is not on the network
65	ENOPKG	Package not installed
66	EREMOTE	Object is remote
67	ENOLINK	Link has been severed
68	EADV	Advertise error
69	ESRMNT	Srmount error
70	ECOMM	Communication error on send
71	EPROTO	Protocol error
72	EMULTIHOP	Multihop attempted
73	EDOTDOT	RFS specific error
74	EBADMSG	Not a data message
75	EOVERFLOW	Value too large for defined data type
76	ENOTUNIQ	Name not unique on network
77	EBADFD	File descriptor in bad state
78	EREMCHG	Remote address changed
79	ELIBACC	Can not access a needed shared library
80	ELIBBAD	Accessing a corrupted shared library
81	ELIBSCN	.lib section in a.out corrupted
82	ELIBMAX	Attempting to link in too many shared libraries
83	ELIBEXEC	Cannot exec a shared library directly
84	EILSEQ	Illegal byte sequence
85	ERESTART	Interrupted system call should be restarted
86	ESTRPIPE	Streams pipe error
87	EUSERS	Too many users
88	ENOTSOCK	Socket operation on non-socket
89	EDESTADDRREQ	Destination address required
90	EMSGSIZE	Message too long
91	EPROTOTYPE	Protocol wrong type for socket
92	ENOPROTOOPT	Protocol not available
93	EPROTONOSUPPORT	Protocol not supported
94	ESOCKTNOSUPPORT	Socket type not supported
95	EOPNOTSUPP	Operation not supported on transport endpoint
96	EPFNOSUPPORT	Protocol family not supported
97	EAFNOSUPPORT	Address family not supported by protocol
98	EADDRINUSE	Address already in use
99	EADDRNOTAVAIL	Cannot assign requested address
100	ENETDOWN	Network is down
101	ENETUNREACH	Network is unreachable
102	ENETRESET	Network dropped connection because of reset
103	ECONNABORTED	Software caused connection abort
104	ECONNRESET	Connection reset by peer
105	ENOBUFS	No buffer space available
106	EISCONN	Transport endpoint is already connected
107	ENOTCONN	Transport endpoint is not connected
108	ESHUTDOWN	Cannot send after transport endpoint shutdown
109	ETOOMANYREFS	Too many references: cannot splice
110	ETIMEDOUT	Connection timed out
111	ECONNREFUSED	Connection refused
112	EHOSTDOWN	Host is down
113	EHOSTUNREACH	No route to host
114	EALREADY	Operation already in progress
115	EINPROGRESS	Operation now in progress
116	ESTALE	Stale NFS file handle
117	EUCLEAN	Structure needs cleaning
118	ENOTNAM	Not a XENIX named type file
119	ENAVAIL	No XENIX semaphores available
120	EISNAM	Is a named type file
121	EREMOTEIO	Remote I/O error
122	EDQUOT	Quota exceeded
123	ENOMEDIUM	No medium found
124	EMEDIUMTYPE	Wrong medium type
125	ECANCELED	Operation Canceled
126	ENOKEY	Required key not available
127	EKEYEXPIRED	Key has expired
128	EKEYREVOKED	Key has been revoked
129	EKEYREJECTED	Key was rejected by service
130	EOWNERDEAD	Owner died
131	ENOTRECOVERABLE	State not recoverable

When you see an error number thrown by a C program on a Linux environment, you might find the above table handy to identify what those error number means. Make sure to bookmark this article for future reference.

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