errno
QNX SDP8.0C Library ReferenceAPIDeveloper
Thread-local error variable
Synopsis:
#include <errno.h>
int errno;
char * const sys_errlist[];
int sys_nerr;
Library:
libc
Use the -l c option to qcc to link against this library. This library is usually included automatically.
Description:
The errno variable is set to certain error values by many functions whenever an error has occurred. This variable may be implemented as a macro, but you can always examine or set it as if it were a simple integer variable.
Note:
- You can't assume that the value of errno is valid unless the description of the function that you've called explicitly states that this variable will be set following an error and the function call itself indicates that an error has occurred. The runtime library never resets errno to 0.
- The documentation for a function might list special meanings for certain values of errno, but this doesn't mean that these are necessarily the only values that the function might set.
-
Each thread in a multi-threaded program has its own error value in its
thread local storage.
No matter which thread you're in, you can simply refer to errno— it's defined
in such a way that it refers to the correct variable for
the thread.
For more information, see
Local storage for private data
in the documentation for ThreadCreate().
The following variables are also defined in <errno.h>:
- sys_errlist
- An array of error messages corresponding to errno.
- sys_nerr
- The number of entries in the sys_errlist array.
The values for errno include at least the following. Some are defined by POSIX, and some are additional values.
Name | Value | Meaning | POSIX? |
---|---|---|---|
E2BIG | 7 | Argument list is too long | Yes |
EACCES | 13 | Permission denied | Yes |
EADDRINUSE | 248 | Address is already in use | Yes |
EADDRNOTAVAIL | 249 | Can't assign requested address | Yes |
EADV | 68 | Advertise error | No |
EAFNOSUPPORT | 247 | Address family isn't supported by protocol family | Yes |
EAGAIN | 11 (same as EWOULDBLOCK) | Resource is temporarily unavailable; try again | Yes |
EALREADY | 237 | Operation is already in progress | Yes |
EBADE | 50 | Invalid exchange | No |
EBADF | 9 | Bad file descriptor | Yes |
EBADFD | 81 | FD is invalid for this operation | No |
EBADFSYS | 302 | Corrupted filesystem detected | No |
EBADMSG | 77 | Bad message | Yes |
EBADR | 51 | Invalid request descriptor | No |
EBADRPC | 272 | RPC struct is bad | No |
EBADRQC | 54 | Invalid request code | No |
EBADSLT | 55 | Invalid slot | No |
EBFONT | 57 | Bad font-file format | No |
EBUSY | 16 | Device or resource is busy | Yes |
ECANCELED | 47 | Operation canceled | Yes |
ECHILD | 10 | No child processes | Yes |
ECHRNG | 37 | Channel number is out of range | No |
ECOMM | 70 | Communication error occurred on send | No |
ECONNABORTED | 253 | Software caused connection to abort | Yes |
ECONNREFUSED | 261 | Connection refused | Yes |
ECONNRESET | 254 | Connection reset by peer | Yes |
ECTRLTERM | 310 | Remap to the controlling terminal | No |
EDEADLK | 45 | Resource deadlock avoided | Yes |
EDEADLOCK | 56 | File locking deadlock | No |
EDESTADDRREQ | 239 | Destination address is required | Yes |
EDOM | 33 | Math argument is out of domain for the function | Yes |
EDQUOT | 49 | Disk quota exceeded | Yes |
EENDIAN | 313 | Endian not supported | No |
EEXIST | 17 | File exists | Yes |
EFAULT | 14 | Bad address | Yes |
EFBIG | 27 | File is too large | Yes |
EFPOS | 110 | File positioning error | No |
EHOSTDOWN | 264 | Host is down | No |
EHOSTUNREACH | 265 | Unable to communicate with remote node | Yes |
EIDRM | 36 | Identifier removed | Yes |
EILSEQ | 88 | Illegal byte sequence | Yes |
EINPROGRESS | 236 | Operation now in progress | Yes |
EINTR | 4 | Interrupted function call | Yes |
EINVAL | 22 | Invalid argument | Yes |
EIO | 5 | I/O error | Yes |
EISCONN | 256 | Socket is already connected | Yes |
EISDIR | 21 | Is a directory | Yes |
EL2HLT | 44 | Level 2 halted | No |
EL2NSYNC | 38 | Level 2 not synchronized | No |
EL3HLT | 39 | Level 3 halted | No |
EL3RST | 40 | Level 3 reset | No |
ELIBACC | 83 | Can't access shared library | No |
ELIBBAD | 84 | Accessing a corrupted shared library | No |
ELIBEXEC | 87 | Attempting to exec a shared library | No |
ELIBMAX | 86 | Attempting to link in too many libraries | No |
ELIBSCN | 85 | The .lib section in a.out is corrupted |
No |
ELNRNG | 41 | Link number is out of range | No |
ELOOP | 90 | Too many levels of symbolic links or prefixes | Yes |
EMFILE | 24 | Too many open files | Yes |
EMLINK | 31 | Too many links | Yes |
EMORE | 309 | More to do, send message again | No |
EMSGSIZE | 240 | Inappropriate message buffer length | Yes |
EMULTIHOP | 74 | Multihop attempted | Yes |
ENAMETOOLONG | 78 | Filename is too long | Yes |
ENETDOWN | 250 | Network is down | Yes |
ENETRESET | 252 | Network dropped connection on reset | Yes |
ENETUNREACH | 251 | Network is unreachable | Yes |
ENFILE | 23 | Too many open files in the system | Yes |
ENOANO | 53 | No anode | No |
ENOBUFS | 255 | No buffer space available | Yes |
ENOCSI | 43 | No CSI structure available | No |
ENODATA | 61 | No data (for no-delay I/O) | Yes |
ENODEV | 19 | No such device | Yes |
ENOENT | 2 | No such file or directory | Yes |
ENOEXEC | 8 | Exec format error | Yes |
ENOLCK | 46 | No locks available | Yes |
ENOLIC | 311 | No license available | No |
ENOLINK | 67 | The link has been severed | Yes |
ENOMEM | 12 | Not enough memory | Yes |
ENOMSG | 35 | No message of desired type | Yes |
ENONDP | 301 | Need an NDP (8087...) to run | No |
ENONET | 64 | Machine isn't on the network | No |
ENOPKG | 65 | Package isn't installed | No |
ENOPROTOOPT | 242 | Protocol isn't available | Yes |
ENOSPC | 28 | No space left on device | Yes |
ENOSR | 63 | Out of streams resources | Yes |
ENOSTR | 60 | Device isn't a stream | Yes |
ENOSYS | 89 | Function isn't implemented | Yes |
ENOTBLK | 15 | A block device is required | No |
ENOTCONN | 257 | Socket isn't connected | Yes |
ENOTDIR | 20 | Not a directory | Yes |
ENOTEMPTY | 93 | Directory isn't empty | Yes |
ENOTRECOVERABLE | 95 | Mutex-protected state not recoverable | Yes |
ENOTSOCK | 238 | Socket operation on nonsocket | Yes |
ENOTSUP | 48 | Not supported | Yes |
ENOTTY | 25 | Inappropriate I/O control operation | Yes |
ENOTUNIQ | 80 | Given name isn't unique | No |
ENXIO | 6 | No such device or address | Yes |
EOK | 0 | No error | No |
EOPNOTSUPP | 103 | Operation isn't supported | Yes |
EOVERFLOW | 79 | Value too large to be stored in data type | Yes |
EOWNERDEAD | 58 | The owner of a lock died while holding it | No |
EPERM | 1 | Operation isn't permitted | Yes |
EPFNOSUPPORT | 246 | Protocol family isn't supported | No |
EPIPE | 32 | Broken pipe | Yes |
EPROCUNAVAIL | 276 | Bad procedure for program | No |
EPROGMISMATCH | 275 | Program version wrong | No |
EPROGUNAVAIL | 274 | RPC program isn't available | No |
EPROTO | 71 | Protocol error | Yes |
EPROTONOSUPPORT | 243 | Protocol isn't supported | Yes |
EPROTOTYPE | 241 | Protocol is wrong type for socket | Yes |
ERANGE | 34 | Result is too large | Yes |
EREMCHG | 82 | Remote address changed | No |
EREMOTE | 66 | The object is remote | No |
ERESTART | 91 | Restartable system call | No |
EROFS | 30 | Read-only filesystem | Yes |
ERPCMISMATCH | 273 | RPC version is wrong | No |
ESHUTDOWN | 258 | Can't send after socket shutdown | No |
ESECTYPEINVAL | 314 | Invalid security type | No |
ESOCKTNOSUPPORT | 244 | Socket type isn't supported | No |
ESPIPE | 29 | Illegal seek | Yes |
ESRCH | 3 | No such process | Yes |
ESRMNT | 69 | Server mount error | No |
ESRVRFAULT | 312 | The receive side of a message transfer encountered a memory fault accessing the receive/reply buffer. | No |
ESTALE | 122 | Potentially recoverable I/O error | Yes |
ESTRPIPE | 92 | If pipe/FIFO, don't sleep in stream head | No |
ETIME | 62 | Timer expired | Yes |
ETIMEDOUT | 260 | Connection timed out | Yes |
ETOOMANYREFS | 259 | Too many references: can't splice | No |
ETXTBSY | 26 | Text file is busy | Yes |
EUNATCH | 42 | Protocol driver isn't attached | No |
EUSERS | 94 | Too many users (for UFS) | No |
EWOULDBLOCK | 11 (same as EAGAIN) | Operation would block | Yes |
EXDEV | 18 | Cross-device link | Yes |
EXFULL | 52 | Exchange full | No |
Examples:
/*
* The following program makes an illegal call
* to the close() function, then prints the
* value held in errno.
*/
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
int main( void )
{
int errvalue;
if( close( -1 ) == -1 ){
errvalue = errno; // preserve value as first printf may change errno
printf( "The error generated was %d\n", errvalue );
printf( "That means: %s\n", strerror( errvalue ) );
}
}
Classification:
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