proposal: x/term: Interruptable ReadLine

[dnbsd]

Proposal Details

Reading a line from a terminal can only be interrupted by the user pressing CTRL+D or CTRL+C. API does not allow the reading to be interrupted via other means. This creates an impossible scenario if other goroutine should be the source of interrupt.

Closing an underlying file (os.Stdin) does not work as expected. A user is still required to touch at least a single key for the closure be detected. And, of course, closing stdin in itself is problematic in more complex programs.

I would like to propose adding a new method Terminal.Close which would terminate blocking ReadLine call, or adding ReadLineWithContext to achieve the same just using context.Context.

package main

import (
	"fmt"
	xterm "golang.org/x/term"
	"io"
	"os"
	"time"
)

var fd = int(os.Stdin.Fd())

func main() {
	origState, err := xterm.GetState(fd)
	if err != nil {
		panic(err)
	}
	defer xterm.Restore(fd, origState)

	term := xterm.NewTerminal(os.Stdin, "> ")

	go func(){
		<-time.After(10*time.Second)
		// Terminate ReadLine here...
	}()

	for {
		oldState, err := xterm.MakeRaw(fd)
		if err != nil {
			panic(err)
		}

		line, err := term.ReadLine()
		if err != nil {
			if err != io.EOF {
				panic(err)
			}
			return
		}

		err = xterm.Restore(fd, oldState)
		if err != nil {
			panic(err)
		}

		fmt.Printf("%q\n", line)
	}
}

[gabyhelp]

Related Issues and Documentation

• x/term: ReadKey() interface #13299
• proposal: os: (*File).SetReadDeadline and (*File).SetWriteDeadline /case: serial interface/ #22100 (closed)
• x/term: Cannot differentiate a CTRL+C from CTRL+D #62385

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[seankhliao]

I don't think this is possible by default, as the function would still be blocked on the read without a way to interrupt it properly. see #24842 and #26579 for related workarounds.