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// Copyright 2021 The age Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//nolint:gocritic // this file is borrowed from age
package termutil
import (
"fmt"
"io"
"os"
"runtime"
"golang.org/x/term"
)
// clearLine clears the current line on the terminal, or opens a new line if
// terminal escape codes don't work.
func clearLine(out io.Writer) {
const (
CUI = "\033[" // Control Sequence Introducer
CPL = CUI + "F" // Cursor Previous Line
EL = CUI + "K" // Erase in Line
)
// First, open a new line, which is guaranteed to work everywhere. Then, try
// to erase the line above with escape codes.
//
// (We use CRLF instead of LF to work around an apparent bug in WSL2's
// handling of CONOUT$. Only when running a Windows binary from WSL2, the
// cursor would not go back to the start of the line with a simple LF.
// Honestly, it's impressive CONIN$ and CONOUT$ work at all inside WSL2.)
fmt.Fprintf(out, "\r\n"+CPL+EL)
}
// withTerminal runs f with the terminal input and output files, if available.
// withTerminal does not open a non-terminal stdin, so the caller does not need
// to check stdinInUse.
func withTerminal(f func(in, out *os.File) error) error {
if runtime.GOOS == "windows" {
in, err := os.OpenFile("CONIN$", os.O_RDWR, 0)
if err != nil {
return err
}
defer in.Close()
out, err := os.OpenFile("CONOUT$", os.O_WRONLY, 0)
if err != nil {
return err
}
defer out.Close()
return f(in, out)
}
var (
tty *os.File
err error
)
if tty, err = os.OpenFile("/dev/tty", os.O_RDWR, 0); err == nil {
defer tty.Close()
return f(tty, tty)
}
if term.IsTerminal(int(os.Stdin.Fd())) {
return f(os.Stdin, os.Stdin)
}
return fmt.Errorf("standard input is not a terminal, and /dev/tty is not available: %w", err)
}
// ReadPassword reads a value from the terminal with no echo. The prompt is
// ephemeral.
func ReadPassword(prompt string) (s []byte, err error) {
err = withTerminal(func(in, out *os.File) error {
fmt.Fprintf(out, "%s ", prompt)
defer clearLine(out)
s, err = term.ReadPassword(int(in.Fd()))
return err
})
return
}
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