module Errno
When an operating system encounters an error, it typically reports the error as an integer error code:
$ ls nosuch.txt ls: cannot access 'nosuch.txt': No such file or directory $ echo $? # Code for last error. 2
When the Ruby interpreter interacts with the operating system and receives such an error code (e.g., 2), it maps the code to a particular Ruby exception class (e.g., Errno::ENOENT):
File.open('nosuch.txt') # => No such file or directory @ rb_sysopen - nosuch.txt (Errno::ENOENT)
Each such class is:
-
A nested class in this module,
Errno. -
A subclass of class
SystemCallError. -
Associated with an error code.
Thus:
Errno::ENOENT.superclass # => SystemCallError Errno::ENOENT::Errno # => 2
The names of nested classes are returned by method Errno.constants:
Errno.constants.size # => 158 Errno.constants.sort.take(5) # => [:E2BIG, :EACCES, :EADDRINUSE, :EADDRNOTAVAIL, :EADV]
As seen above, the error code associated with each class is available as the value of a constant; the value for a particular class may vary among operating systems. If the class is not needed for the particular operating system, the value is zero:
Errno::ENOENT::Errno # => 2 Errno::ENOTCAPABLE::Errno # => 0
Constants
- E2BIG
“Argument list too long” error
- EACCES
“Permission denied” error
- EADDRINUSE
“Address already in use” error
- EADDRNOTAVAIL
“Address not available” error
- EADV
“Advertise error” error
- EAFNOSUPPORT
“Address family not supported” error
- EAGAIN
“Resource temporarily unavailable, try again (may be the same value as
EWOULDBLOCK)” error- EALREADY
“Connection already in progress” error
- EAUTH
“Authentication error” error
- EBADARCH
“Bad CPU type in executable” error
- EBADE
“Bad exchange” error
- EBADEXEC
“Bad executable” error
- EBADF
“Bad file descriptor” error
- EBADFD
“File descriptor in bad state” error
- EBADMACHO
“Malformed Macho file” error
- EBADMSG
“Bad message” error
- EBADR
“Invalid request descriptor” error
- EBADRPC
“RPC struct is bad” error
- EBADRQC
“Invalid request code” error
- EBADSLT
“Invalid slot” error
- EBFONT
“Bad font file format” error
- EBUSY
“Device or resource busy” error
- ECANCELED
“Operation canceled” error
- ECAPMODE
“Not permitted in capability mode” error
- ECHILD
“No child processes” error
- ECHRNG
“Channel number out of range” error
- ECOMM
“Communication error on send” error
- ECONNABORTED
“Connection aborted” error
- ECONNREFUSED
“Connection refused” error
- ECONNRESET
“Connection reset” error
- EDEADLK
“Resource deadlock avoided” error
- EDEADLOCK
“File locking deadlock error” error
- EDESTADDRREQ
“Destination address required” error
- EDEVERR
“Device error; e.g., printer paper out” error
- EDOM
“Mathematics argument out of domain of function” error
- EDOOFUS
“Improper function use” error
- EDOTDOT
“RFS specific error” error
- EDQUOT
“Disk quota exceeded” error
- EEXIST
“File exists” error
- EFAULT
“Bad address” error
- EFBIG
“File too large” error
- EFTYPE
“Invalid file type or format” error
- EHOSTDOWN
“Host is down” error
- EHOSTUNREACH
“Host is unreachable” error
- EHWPOISON
“Memory page has hardware error” error
- EIDRM
“Identifier removed” error
- EILSEQ
“Invalid or incomplete multibyte or wide character” error
- EINPROGRESS
“Operation in progress” error
- EINTR
“Interrupted function call” error
- EINVAL
“Invalid argument” error
- EIO
“Input/output error” error
- EIPSEC
“IPsec processing failure” error
- EISCONN
“Socket is connected” error
- EISDIR
“Is a directory” error
- EISNAM
“Is a named file type” error
- EKEYEXPIRED
“Key has expired” error
- EKEYREJECTED
“Key was rejected by service” error
- EKEYREVOKED
“Key has been revoked” error
- EL2HLT
“Level 2 halted” error
- EL2NSYNC
“Level 2 not synchronized” error
- EL3HLT
“Level 3 halted” error
- EL3RST
“Level 3 reset” error
- ELAST
“Largest errno value” error
- ELIBACC
“Cannot access a needed shared library” error
- ELIBBAD
“Accessing a corrupted shared library” error
- ELIBEXEC
“Cannot exec a shared library directly” error
- ELIBMAX
“Attempting to link in too many shared libraries” error
- ELIBSCN
“.lib section in a.out corrupted” error
- ELNRNG
“Link number out of range” error
- ELOOP
“Too many levels of symbolic links” error
- EMEDIUMTYPE
“Wrong medium type” error
- EMFILE
“Too many open files” error
- EMLINK
“Too many links” error
- EMSGSIZE
“Message too long” error
- EMULTIHOP
“Multihop attempted” error
- ENAMETOOLONG
“Filename too long” error
- ENAVAIL
“No XENIX semaphores available” error
- ENEEDAUTH
“Need authenticator” error
- ENETDOWN
“Network is down” error
- ENETRESET
“Connection aborted by network” error
- ENETUNREACH
“Network unreachable” error
- ENFILE
“Too many open files in system” error
- ENOANO
“No anode” error
- ENOATTR
“Attribute not found” error
- ENOBUFS
“No buffer space available” error
- ENOCSI
“No CSI structure available” error
- ENODATA
“No data available” error
- ENODEV
“No such device” error
- ENOENT
“No such file or directory” error
- ENOEXEC
“Exec format error” error
- ENOKEY
“Required key not available” error
- ENOLCK
“No locks available” error
- ENOLINK
“Link has been severed” error
- ENOMEDIUM
“No medium found” error
- ENOMEM
“Not enough space/cannot allocate memory” error
- ENOMSG
“No message of the desired type” error
- ENONET
“Machine is not on the network” error
- ENOPKG
“Package not installed” error
- ENOPOLICY
“No such policy” error
- ENOPROTOOPT
“Protocol not available” error
- ENOSPC
“No space left on device” error
- ENOSR
“No STREAM resources” error
- ENOSTR
“Not a STREAM” error
- ENOSYS
“Functionality not implemented” error
- ENOTBLK
“Block device required” error
- ENOTCAPABLE
“Capabilities insufficient” error
- ENOTCONN
“The socket is not connected” error
- ENOTDIR
“Not a directory” error
- ENOTEMPTY
“Directory not empty” error
- ENOTNAM
“Not a XENIX named type file” error
- ENOTRECOVERABLE
“State not recoverable” error
- ENOTSOCK
“Not a socket” error
- ENOTSUP
“Operation not supported” error
- ENOTTY
“Inappropriate I/O control operation” error
- ENOTUNIQ
“Name not unique on network” error
- ENXIO
“No such device or address” error
- EOPNOTSUPP
“Operation not supported on socket” error
- EOVERFLOW
“Value too large to be stored in data type” error
- EOWNERDEAD
“Owner died” error
- EPERM
“Operation not permitted” error
- EPFNOSUPPORT
“Protocol family not supported” error
- EPIPE
“Broken pipe” error
- EPROCLIM
“Too many processes” error
- EPROCUNAVAIL
“Bad procedure for program” error
- EPROGMISMATCH
“Program version wrong” error
- EPROGUNAVAIL
“RPC program isn’t available” error
- EPROTO
“Protocol error” error
- EPROTONOSUPPORT
“Protocol not supported” error
- EPROTOTYPE
“Protocol wrong type for socket” error
- EPWROFF
“Device power is off” error
- EQFULL
“Interface output queue is full” error
- ERANGE
“Result too large” error
- EREMCHG
“Remote address changed” error
- EREMOTE
“Object is remote” error
- EREMOTEIO
“Remote I/O error” error
- ERESTART
“Interrupted system call should be restarted” error
- ERFKILL
“Operation not possible due to RF-kill” error
- EROFS
“Read-only file system” error
- ERPCMISMATCH
“RPC version wrong” error
- ESHLIBVERS
“Shared library version mismatch” error
- ESHUTDOWN
“Cannot send after transport endpoint shutdown” error
- ESOCKTNOSUPPORT
“Socket type not supported” error
- ESPIPE
“Illegal seek” error
- ESRCH
“No such process” error
- ESRMNT
“Server mount error” error
- ESTALE
“Stale file handle” error
- ESTRPIPE
“Streams pipe error” error
- ETIME
“Timer expired” error
- ETIMEDOUT
“Connection timed out” error
- ETOOMANYREFS
cannot splice“ error
- ETXTBSY
“Text file busy” error
- EUCLEAN
“Structure needs cleaning” error
- EUNATCH
“Protocol driver not attached” error
- EUSERS
“Too many users” error
- EWOULDBLOCK
“Operation would block” error
- EXDEV
“Invalid cross-device link” error
- EXFULL
“Exchange full” error
- NOERROR
No error