util: password: Add a cancellable ReadPassword style functions
It was non-trivial to do this, so I put it into a library. Strangely I couldn't directly wrap the ReadPassword function from the golang.org/x/term package, as it wouldn't unblock for some reason.
This commit is contained in:
James Shubin
141
util/password/password.go
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141
util/password/password.go
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@@ -0,0 +1,141 @@
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// Mgmt
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// Copyright (C) 2013-2023+ James Shubin and the project contributors
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// Written by James Shubin <james@shubin.ca> and the project contributors
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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package password
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import (
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"context"
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"errors"
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"fmt"
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"io"
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"os"
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"runtime"
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"sync"
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"syscall"
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"time"
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"golang.org/x/sys/unix"
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)
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const (
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// StdPrompt is the usual text that we would use to ask for a password.
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StdPrompt = "Password: "
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// XXX: these two are different on BSD, and were taken from:
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// golang.org/x/term/term_unix_other.go
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ioctlReadTermios = unix.TCGETS
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ioctlWriteTermios = unix.TCSETS
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)
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// ReadPassword reads a password from stdin and returns the result. It hides the
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// display of the password typed. For more options try ReadPasswordCtxFdPrompt
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// instead. If interrupted by an uncaught signal during read, then this can bork
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// your terminal. It's best to use a version with a context instead.
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func ReadPassword() ([]byte, error) {
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return ReadPasswordCtxFdPrompt(context.Background(), int(os.Stdin.Fd()), StdPrompt)
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}
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// ReadPasswordCtx reads a password from stdin and returns the result. It hides
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// the display of the password typed. It cancels reading when the context
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// closes. For more options try ReadPasswordCtxFdPrompt instead. If interrupted
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// by an uncaught signal during read, then this can bork your terminal. It's
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// best to use a version with a context instead.
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func ReadPasswordCtx(ctx context.Context) ([]byte, error) {
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return ReadPasswordCtxFdPrompt(ctx, int(os.Stdin.Fd()), StdPrompt)
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}
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// ReadPasswordCtxFdPrompt reads a password from the file descriptor and returns
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// the result. It hides the display of the password typed. It cancels reading
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// when the context closes. If specified, it will prompt the user with the
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// prompt message. If interrupted by an uncaught signal during read, then this
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// can bork your terminal.
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func ReadPasswordCtxFdPrompt(ctx context.Context, fd int, prompt string) ([]byte, error) {
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// XXX: https://github.com/golang/go/issues/24842
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if err := syscall.SetNonblock(fd, true); err != nil {
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return nil, err
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}
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file := os.NewFile(uintptr(fd), "") // XXX: name?
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// We do some term magic to not print the password. This is taken from:
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// golang.org/x/term/term_unix.go:readPassword
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termios, err := unix.IoctlGetTermios(fd, ioctlReadTermios)
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if err != nil {
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return nil, err
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}
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newState := *termios
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newState.Lflag &^= unix.ECHO
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newState.Lflag |= unix.ICANON | unix.ISIG
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newState.Iflag |= unix.ICRNL
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if err := unix.IoctlSetTermios(fd, ioctlWriteTermios, &newState); err != nil {
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return nil, err
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}
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defer unix.IoctlSetTermios(fd, ioctlWriteTermios, termios)
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wg := &sync.WaitGroup{}
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defer wg.Wait()
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ctx, cancel := context.WithCancel(ctx)
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defer cancel()
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wg.Add(1)
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go func() {
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defer wg.Done()
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<-ctx.Done()
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file.SetReadDeadline(time.Now())
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}()
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if prompt != "" {
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fmt.Print(prompt) // prints because we only turned off echo on fd
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}
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// This previously didn't pass through the deadline. This is taken from:
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// golang.org/x/term/terminal.go:readPasswordLine
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var buf [1]byte
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var ret []byte
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for {
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n, err := file.Read(buf[:]) // unblocks on SetReadDeadline(now)
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if n > 0 {
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switch buf[0] {
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case '\b':
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if len(ret) > 0 {
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ret = ret[:len(ret)-1]
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}
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case '\n':
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if runtime.GOOS != "windows" {
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return ret, nil
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}
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// otherwise ignore \n
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case '\r': // lol
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if runtime.GOOS == "windows" {
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return ret, nil
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}
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// otherwise ignore \r
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default:
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ret = append(ret, buf[0])
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}
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continue
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}
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if e := ctx.Err(); errors.Is(err, os.ErrDeadlineExceeded) && e != nil {
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return nil, e
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}
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if err != nil {
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if err == io.EOF && len(ret) > 0 {
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return ret, nil
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}
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return ret, err // XXX: why ret and not nil?
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}
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}
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}
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68
util/password/password_test.go
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68
util/password/password_test.go
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@@ -0,0 +1,68 @@
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// Mgmt
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// Copyright (C) 2013-2023+ James Shubin and the project contributors
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// Written by James Shubin <james@shubin.ca> and the project contributors
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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//go:build !root
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package password
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import (
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"context"
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"fmt"
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"os"
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"os/signal"
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"sync"
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"syscall"
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"time"
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)
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func ExampleReadPasswordCtx() {
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// Put this in a main function and it will not have the ioctl error!
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fmt.Println("hello")
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defer fmt.Println("exiting...")
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wg := &sync.WaitGroup{}
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defer wg.Wait()
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ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
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defer cancel()
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// If we exit without getting a chance to reset the terminal, it might
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// be borked!
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ch := make(chan os.Signal, 1+1) // must have buffer for max number of signals
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signal.Notify(ch, syscall.SIGTERM, os.Interrupt)
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wg.Add(1)
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go func() {
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defer wg.Done()
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select {
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case <-ch:
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cancel()
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case <-ctx.Done():
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}
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}()
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password, err := ReadPasswordCtx(ctx)
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if err != nil {
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fmt.Printf("error: %+v\n", err)
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return
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}
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fmt.Printf("password is: %s\n", string(password))
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// Output: hello
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// error: inappropriate ioctl for device
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// exiting...
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}
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