Ruby exception objects are subclasses of Exception. However, operating systems typically report errors using plain integers. Module Errno is created dynamically to map these operating system errors to Ruby classes, with each error number generating its own subclass of SystemCallError. As the subclass is created in module Errno, its name will start Errno::.
The names of the Errno:: classes depend on the environment in which Ruby runs. On a typical Unix or Windows platform, there are Errno classes such as Errno::EACCES, Errno::EAGAIN, Errno::EINTR, and so on.
The integer operating system error number corresponding to a particular error is available as the class constant Errno::error::Errno.
Errno::EACCES::Errno #=> 13 Errno::EAGAIN::Errno #=> 11 Errno::EINTR::Errno #=> 4
The full list of operating system errors on your particular platform are available as the constants of Errno.
Errno.constants #=> :E2BIG, :EACCES, :EADDRINUSE, :EADDRNOTAVAIL, ...
No error
“Argument list too long” error
“Permission denied” error
“Address in use” error
“Address not available” error
EADV error
“Address family not supported” error
“Resource unavailable, try again (may be the same value as [EWOULDBLOCK])” error
“Connection already in progress” error
EAUTH error
EBADARCH error
EBADE error
EBADEXEC error
“Bad file descriptor” error
EBADFD error
EBADMACHO error
“Bad message” error
EBADR error
EBADRPC error
EBADRQC error
EBADSLT error
EBFONT error
“Device or resource busy” error
“Operation canceled” error
ECAPMODE error
“No child processes” error
ECHRNG error
ECOMM error
“Connection aborted” error
“Connection refused” error
“Connection reset” error
“Resource deadlock would occur” error
EDEADLOCK error
“Destination address required” error
EDEVERR error
“Mathematics argument out of domain of function” error
EDOOFUS error
EDOTDOT error
“Reserved” error
“File exists” error
“Bad address” error
“File too large” error
EFTYPE error
EHOSTDOWN error
“Host is unreachable” error
EHWPOISON error
“Identifier removed” error
“Illegal byte sequence” error
“Operation in progress” error
“Interrupted function” error
“Invalid argument” error
“I/O error” error
EIPSEC error
“Socket is connected” error
“Is a directory” error
EISNAM error
EKEYEXPIRED error
EKEYREJECTED error
EKEYREVOKED error
EL2HLT error
EL2NSYNC error
EL3HLT error
EL3RST error
ELIBACC error
ELIBBAD error
ELIBEXEC error
ELIBMAX error
ELIBSCN error
ELNRNG error
“Too many levels of symbolic links” error
EMEDIUMTYPE error
“File descriptor value too large” error
“Too many links” error
“Message too large” error
“Reserved” error
“Filename too long” error
ENAVAIL error
ENEEDAUTH error
“Network is down” error
“Connection aborted by network” error
“Network unreachable” error
“Too many files open in system” error
ENOANO error
ENOATTR error
“No buffer space available” error
ENOCSI error
“[OB XSR] [Option Start] No message is available on the STREAM head read queue [Option End]” error
“No such device” error
“No such file or directory” error
“Executable file format error” error
ENOKEY error
“No locks available” error
“Reserved” error
ENOMEDIUM error
“Not enough space” error
“No message of the desired type” error
ENONET error
ENOPKG error
ENOPOLICY error
“Protocol not available” error
“No space left on device” error
“[OB XSR] [Option Start] No STREAM resources [Option End]” error
“[OB XSR] [Option Start] Not a STREAM [Option End]” error
“Functionality not supported” error
ENOTBLK error
ENOTCAPABLE error
“The socket is not connected” error
“Not a directory or a symbolic link to a directory” error
“Directory not empty” error
ENOTNAM error
“State not recoverable” error
“Not a socket” error
“Not supported (may be the same value as [EOPNOTSUPP])” error
“Inappropriate I/O control operation” error
ENOTUNIQ error
“No such device or address” error
“Operation not supported on socket (may be the same value as [ENOTSUP])” error
“Value too large to be stored in data type” error
“Previous owner died” error
“Operation not permitted” error
EPFNOSUPPORT error
“Broken pipe” error
EPROCLIM error
EPROCUNAVAIL error
EPROGMISMATCH error
EPROGUNAVAIL error
“Protocol error” error
“Protocol not supported” error
“Protocol wrong type for socket” error
EPWROFF error
EQFULL error
“Result too large” error
EREMCHG error
EREMOTE error
EREMOTEIO error
ERESTART error
ERFKILL error
“Read-only file system” error
ERPCMISMATCH error
ESHLIBVERS error
ESHUTDOWN error
ESOCKTNOSUPPORT error
“Invalid seek” error
“No such process” error
ESRMNT error
“Reserved” error
ESTRPIPE error
“[OB XSR] [Option Start] Stream ioctl() timeout [Option End]” error
“Connection timed out” error
ETOOMANYREFS error
“Text file busy” error
EUCLEAN error
EUNATCH error
EUSERS error
“Operation would block (may be the same value as [EAGAIN])” error
“Cross-device link” error
EXFULL error
“Largest errno” error