The signals listed in this section are used in conjunction with
asynchronous I/O facilities. You have to take explicit action by
fcntl to enable a particular file descriptor to generate
these signals (see Interrupt Input). The default action for these
signals is to ignore them.
This signal is sent when a file descriptor is ready to perform input or output.
On most operating systems, terminals and sockets are the only kinds of
files that can generate
SIGIO; other kinds, including ordinary
files, never generate
SIGIO even if you ask them to.
On GNU systems
SIGIO will always be generated properly
if you successfully set asynchronous mode with
This signal is sent when “urgent” or out-of-band data arrives on a socket. See Out-of-Band Data.
This is a System V signal name, more or less similar to
It is defined only for compatibility.