simple ioctl FIONREAD example.

gistfile1.go

package main

import (
	"fmt"
	"os"
	"syscall"
	"unsafe"
)

var (
	errEAGAIN error = syscall.EAGAIN
	errEINVAL error = syscall.EINVAL
	errENOENT error = syscall.ENOENT
)

func errnoErr(e syscall.Errno) error {
	switch e {
	case 0:
		return nil
	case syscall.EAGAIN:
		return errEAGAIN
	case syscall.EINVAL:
		return errEINVAL
	case syscall.ENOENT:
		return errENOENT
	}
	return e
}

func ioctl(fd int, request int, argp *int) (err error) {
	_, _, e1 := syscall.Syscall(syscall.SYS_IOCTL,
		uintptr(fd),
		uintptr(request),
		uintptr(unsafe.Pointer(argp)))
	if e1 != 0 {
		err = errnoErr(e1)
	}
	return
}

func main() {
	file, err := os.Open("idk.c")
	if err != nil {
		panic(err)
	}
	defer file.Close()

	n := 0
	err = ioctl(int(file.Fd()), 0x541B, &n)
	fmt.Println(n)
}