IOError

Raised when an IO operation fails.

File .open("/etc/hosts") {|f| f << "example"}
 #=> IOError: not opened for writing
File .open("/etc/hosts") {|f| f.close; f.read }
 #=> IOError: closed stream

Note that some IO failures raise SystemCallErrors and these are not subclasses of IOError:

File .open("does/not/exist")
 #=> Errno::ENOENT: No such file or directory - does/not/exist