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ERRNO(3) | Linux Programmer's Manual | ERRNO(3) |
NAME¶
errno - number of last errorSYNOPSIS¶
#include <errno.h>DESCRIPTION¶
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 return value of the call indicated an error (i.e., -1 from most system calls; -1 or NULL from most library functions); a function that succeeds is allowed to change errno.- E2BIG
- Argument list too long (POSIX.1)
- 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)
- EAGAIN
- Resource temporarily unavailable (may be the same value as EWOULDBLOCK) (POSIX.1)
- EALREADY
- Connection already in progress (POSIX.1)
- EBADE
- Invalid exchange
- EBADF
- Bad file descriptor (POSIX.1)
- EBADFD
- File descriptor in bad state
- EBADMSG
- Bad message (POSIX.1)
- EBADR
- Invalid request descriptor
- EBADRQC
- Invalid request code
- EBADSLT
- Invalid slot
- EBUSY
- Device or resource busy (POSIX.1)
- ECANCELED
- Operation canceled (POSIX.1)
- ECHILD
- No child processes (POSIX.1)
- ECHRNG
- Channel number out of range
- 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)
- EDOM
- Mathematics argument out of domain of function (POSIX.1, C99)
- EDQUOT
- Disk quota exceeded (POSIX.1)
- EEXIST
- File exists (POSIX.1)
- EFAULT
- Bad address (POSIX.1)
- EFBIG
- File too large (POSIX.1)
- EHOSTDOWN
- Host is down
- EHOSTUNREACH
- Host is unreachable (POSIX.1)
- EIDRM
- Identifier removed (POSIX.1)
- EILSEQ
- Illegal byte sequence (POSIX.1, C99)
- EINPROGRESS
- Operation in progress (POSIX.1)
- EINTR
- Interrupted function call (POSIX.1); see signal(7).
- EINVAL
- Invalid argument (POSIX.1)
- EIO
- Input/output error (POSIX.1)
- EISCONN
- Socket is connected (POSIX.1)
- EISDIR
- Is a directory (POSIX.1)
- EISNAM
- Is a named type file
- EKEYEXPIRED
- Key has expired
- EKEYREJECTED
- Key was rejected by service
- EKEYREVOKED
- Key has been revoked
- EL2HLT
- Level 2 halted
- EL2NSYNC
- Level 2 not synchronized
- EL3HLT
- Level 3 halted
- 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
- ELOOP
- Too many levels of symbolic links (POSIX.1)
- EMEDIUMTYPE
- Wrong medium type
- EMFILE
- Too many open files (POSIX.1)
- 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)
- 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)
- ENODEV
- No such device (POSIX.1)
- ENOENT
- No such file or directory (POSIX.1)
- ENOEXEC
- Exec format error (POSIX.1)
- ENOKEY
- Required key not available
- ENOLCK
- No locks available (POSIX.1)
- ENOLINK
- Link has been severed (POSIX.1)
- ENOMEDIUM
- No medium found
- ENOMEM
- Not enough space (POSIX.1)
- ENOMSG
- No message of the desired type (POSIX.1)
- ENONET
- Machine is not on the network
- ENOPKG
- Package not installed
- ENOPROTOOPT
- Protocol not available (POSIX.1)
- ENOSPC
- No space left on device (POSIX.1)
- ENOSR
- No STREAM resources (POSIX.1 (XSI STREAMS option))
- ENOSTR
- Not a STREAM (POSIX.1 (XSI STREAMS option))
- 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)
- ENOTTY
- Inappropriate I/O control operation (POSIX.1)
- ENOTUNIQ
- Name not unique on network
- ENXIO
- No such device or address (POSIX.1)
- EOPNOTSUPP
- Operation not supported on socket (POSIX.1)
- EOVERFLOW
- Value too large to be stored in data type (POSIX.1)
- EPERM
- Operation not permitted (POSIX.1)
- EPFNOSUPPORT
- Protocol family not supported
- EPIPE
- Broken pipe (POSIX.1)
- EPROTO
- Protocol error (POSIX.1)
- EPROTONOSUPPORT
- Protocol not supported (POSIX.1)
- EPROTOTYPE
- Protocol wrong type for socket (POSIX.1)
- 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
- EROFS
- Read-only file system (POSIX.1)
- ESHUTDOWN
- Cannot send after transport endpoint shutdown
- ESPIPE
- Invalid seek (POSIX.1)
- ESOCKTNOSUPPORT
- Socket type not supported
- ESRCH
- No such process (POSIX.1)
- ESTALE
- Stale file handle (POSIX.1)
- ESTRPIPE
- Streams pipe error
- ETIME
- Timer expired (POSIX.1 (XSI STREAMS option))
- ETIMEDOUT
- Connection timed out (POSIX.1)
- ETXTBSY
- Text file busy (POSIX.1)
- EUCLEAN
- Structure needs cleaning
- EUNATCH
- Protocol driver not attached
- EUSERS
- Too many users
- EWOULDBLOCK
- Operation would block (may be same value as EAGAIN) (POSIX.1)
- EXDEV
- Improper link (POSIX.1)
- EXFULL
- Exchange full
NOTES¶
A common mistake is to doif (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(3)). 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.
SEE ALSO¶
err(3), error(3), perror(3), strerror(3)COLOPHON¶
This page is part of release 3.44 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.2008-07-09 |