GNU/Linux man pages
Livre :
Expressions régulières,
Syntaxe et mise en oeuvre :
GNU/Linux |
CentOS 5.5 |
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errno(3) |
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errno − number of last error
#include <errno.h>
The <errno.h> header file defines the integer variable errno, which is set by system calls and some library functions in the event of an error to indicate what went wrong. Its value is significant only when the call returned an error (usually −1), and a function that does succeed is allowed to change errno.
Sometimes, when −1 is also a valid successful return value one has to zero errno before the call in order to detect possible errors.
errno is defined by the ISO C standard to be a modifiable lvalue of type int, and must not be explicitly declared; errno may be a macro. errno is thread-local; setting it in one thread does not affect its value in any other thread.
Valid error numbers are all non-zero; errno is never set to zero by any library function. All the error names specified by POSIX.1 must have distinct values, with the exception of EAGAIN and EWOULDBLOCK, which may be the same.
Below is a list of the symbolic error names that are defined on Linux. Some of these are marked POSIX.1, indicating that the name is defined by POSIX.1-2001, or C99, indicating that the name is defined by C99.
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E2BIG |
Argument list too long (POSIX.1) |
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EACCES |
Permission denied (POSIX.1) |
EADDRINUSE
Address already in use (POSIX.1)
EADDRNOTAVAIL
Address not available (POSIX.1)
EAFNOSUPPORT
Address family not supported (POSIX.1)
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EAGAIN |
Resource temporarily unavailable (may be the same value as EWOULDBLOCK) (POSIX.1) |
EALREADY
Connection already in progress (POSIX.1)
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EBADE |
Invalid exchange |
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EBADF |
Bad file descriptor (POSIX.1) |
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EBADFD |
File descriptor in bad state |
EBADMSG
Bad message (POSIX.1)
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EBADR |
Invalid request descriptor |
EBADRQC
Invalid request code
EBADSLT
Invalid slot
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EBUSY |
Device or resource busy (POSIX.1) |
ECANCELED
Operation canceled (POSIX.1)
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ECHILD |
No child processes (POSIX.1) |
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ECHRNG |
Channel number out of range |
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ECOMM |
Communication error on send |
ECONNABORTED
Connection aborted (POSIX.1)
ECONNREFUSED
Connection refused (POSIX.1)
ECONNRESET
Connection reset (POSIX.1)
EDEADLK
Resource deadlock avoided (POSIX.1)
EDEADLOCK
Synonym for EDEADLK
EDESTADDRREQ
Destination address required (POSIX.1)
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EDOM |
Mathematics argument out of domain of function (POSIX.1, C99) | ||
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EDQUOT |
Disk quota exceeded (POSIX.1) | ||
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EEXIST |
File exists (POSIX.1) | ||
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EFAULT |
Bad address (POSIX.1) | ||
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EFBIG |
File too large (POSIX.1) |
EHOSTDOWN
Host is down
EHOSTUNREACH
Host is unreachable (POSIX.1)
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EIDRM |
Identifier removed (POSIX.1) |
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EILSEQ |
Illegal byte sequence (POSIX.1, C99) |
EINPROGRESS
Operation in progress (POSIX.1)
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EINTR |
Interrupted function call (POSIX.1) |
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EINVAL |
Invalid argument (POSIX.1) |
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EIO |
Input/output error (POSIX.1) |
EISCONN
Socket is connected (POSIX.1)
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EISDIR |
Is a directory (POSIX.1) |
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EISNAM |
Is a named type file |
EKEYEXPIRED
Key has expired
EKEYREJECTED
Key was rejected by service
EKEYREVOKED
Key has been revoked
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EL2HLT |
Level 2 halted |
EL2NSYNC
Level 2 not synchronized
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EL3HLT |
Level 3 halted |
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EL3RST |
Level 3 halted |
ELIBACC
Cannot access a needed shared library
ELIBBAD
Accessing a corrupted shared library
ELIBMAX
Attempting to link in too many shared libraries
ELIBSCN
lib section in a.out corrupted
ELIBEXEC
Cannot exec a shared library directly
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ELOOP |
Too many levels of symbolic links (POSIX.1) |
EMEDIUMTYPE
Wrong medium type
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EMFILE |
Too many open files (POSIX.1) |
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EMLINK |
Too many links (POSIX.1) |
EMSGSIZE
Message too long (POSIX.1)
EMULTIHOP
Multihop attempted (POSIX.1)
ENAMETOOLONG
Filename too long (POSIX.1)
ENETDOWN
Network is down (POSIX.1)
ENETRESET
Connection aborted by network (POSIX.1)
ENETUNREACH
Network unreachable (POSIX.1)
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ENFILE |
Too many open files in system (POSIX.1) |
ENOBUFS
No buffer space available (POSIX.1 (XSI STREAMS option))
ENODATA
No message is available on the STREAM head read queue (POSIX.1)
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ENODEV |
No such device (POSIX.1) |
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ENOENT |
No such file or directory (POSIX.1) |
ENOEXEC
Exec format error (POSIX.1)
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ENOKEY |
Required key not available |
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ENOLCK |
No locks available (POSIX.1) |
ENOLINK
Link has been severed (POSIX.1)
ENOMEDIUM
No medium found
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ENOMEM |
Not enough space (POSIX.1) |
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ENOMSG |
No message of the desired type (POSIX.1) |
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ENONET |
Machine is not on the network |
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ENOPKG |
Package not installed |
ENOPROTOOPT
Protocol not available (POSIX.1)
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ENOSPC |
No space left on device (POSIX.1) |
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ENOSR |
No STREAM resources (POSIX.1 (XSI STREAMS option)) |
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ENOSTR |
Not a STREAM (POSIX.1 (XSI STREAMS option)) |
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ENOSYS |
Function not implemented (POSIX.1) |
ENOTBLK
Block device required
ENOTCONN
The socket is not connected (POSIX.1)
ENOTDIR
Not a directory (POSIX.1)
ENOTEMPTY
Directory not empty (POSIX.1)
ENOTSOCK
Not a socket (POSIX.1)
ENOTSUP
Operation not supported (POSIX.1)
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ENOTTY |
Inappropriate I/O control operation (POSIX.1) |
ENOTUNIQ
Name not unique on network
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ENXIO |
No such device or address (POSIX.1) |
EOPNOTSUPP
Operation not supported on socket (POSIX.1)
(ENOTSUP and EOPNOTSUPP have the same value on Linux, but according to POSIX.1 these error values should be distinct.)
EOVERFLOW
Value too large to be stored in data type (POSIX.1)
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EPERM |
Operation not permitted (POSIX.1) |
EPFNOSUPPORT
Protocol family not supported
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EPIPE |
Broken pipe (POSIX.1) |
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EPROTO |
Protocol error (POSIX.1) |
EPROTONOSUPPORT
Protocol not supported (POSIX.1)
EPROTOTYPE
Protocol wrong type for socket (POSIX.1)
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ERANGE |
Result too large (POSIX.1, C99) |
EREMCHG
Remote address changed
EREMOTE
Object is remote
EREMOTEIO
Remote I/O error
ERESTART
Interrupted system call should be restarted
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EROFS |
Read-only file system (POSIX.1) |
ESHUTDOWN
Cannot send after transport endpoint shutdown
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ESPIPE |
Invalid seek (POSIX.1) |
ESOCKTNOSUPPORT
Socket type not supported
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ESRCH |
No such process (POSIX.1) |
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ESTALE |
Stale file handle (POSIX.1)) |
This error can occur for NFS and for other file systems
ESTRPIPE
Streams pipe error
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ETIME |
Timer expired (POSIX.1 (XSI STREAMS option)) |
(POSIX.1 says "STREAM ioctl() timeout")
ETIMEDOUT
Connection timed out (POSIX.1)
ETXTBSY
Text file busy (POSIX.1)
EUCLEAN
Structure needs cleaning
EUNATCH
Protocol driver not attached
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EUSERS |
Too many users |
EWOULDBLOCK
Operation would block (may be same value as EAGAIN) (POSIX.1)
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EXDEV |
Improper link (POSIX.1) |
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EXFULL |
Exchange full |
A common mistake is to do
if (somecall()
== −1) {
printf("somecall() failed\n");
if (errno == ...) { ... }
}
where errno no longer needs to have the value it had upon return from somecall() (i.e., it may have been changed by the printf()). If the value of errno should be preserved across a library call, it must be saved:
if (somecall()
== −1) {
int errsv = errno;
printf("somecall() failed\n");
if (errsv == ...) { ... }
}
It was common in traditional C to declare errno manually (i.e., extern int errno) instead of including <errno.h>. Do not do this. It will not work with modern versions of the C library. However, on (very) old Unix systems, there may be no <errno.h> and the declaration is needed.
err(3), error(3), perror(3), strerror(3)
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errno(3) | |