"The general strategy for implementing

isatty

is to attempt a tty-specific

ioctl

operation on the file descriptor, and check for

ENOTTY

error result. Traditionally,

TCGETS

, which is the backend for the

tcgetattr

function, is used, but this is slightly dangerous since the

ioctl

number for it on Linux clashes with legacy OSS sound devices, and if the file descriptor actually refers to a certain type of MIDI device, it will make changes to the device"