Golang: Write a message to any console's input on POSIX.

write_to_stdin_posix.go

// Used in https://github.com/SCP002/terminator.
// For Windows, see: https://gist.github.com/SCP002/1b7fd91a519a2dc60fc5b179f90472b6.

package main

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

	"github.com/shirou/gopsutil/v3/process"
)

func main() {
	var pid int
	fmt.Print("PID: ")
	fmt.Scanln(&pid)
	err := Write(pid, "Hello, World!\n")
	if err != nil {
		panic(err)
	}
}

// Write writes a message to the console's input.
//
// Requires root privilegies (e.g. run as sudo).
func Write(pid int, msg string) error {
	proc, err := process.NewProcess(int32(pid))
	if err != nil {
		return err
	}
	term, err := proc.Terminal()
	if err != nil {
		return err
	}
	f, err := os.OpenFile("/dev" + term, os.O_WRONLY, 0644)
	if err != nil {
		return err
	}
	defer f.Close()
	for _, c := range msg {
		_, _, err := syscall.Syscall(syscall.SYS_IOCTL, f.Fd(), syscall.TIOCSTI, uintptr(unsafe.Pointer(&c)))
		if err != 0 {
			return err
		}
	}
	return nil
}