[Chapter 3] 3.6 Stop Accidental Bourne Shell Logouts
Author: Jerry Peek, Tim O'Reilly & Mike Loukides
Date: 1998-08-04T21:32:34Z

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| Chapter 3 Logging Out |

## 3.6 Stop Accidental Bourne Shell Logouts

It's pretty easy to type one too many CTRL-d characters and log out of a Bourne shell without meaning to. The C shell has an ignoreeof shell variable (3.5) that won't let you log out with CTRL-d. So do the Korn shell and bash; use `set -o ignoreeof`.

Here's a different sort of solution for the Bourne shell. When you end the shell, it asks if you're sure. If you don't answer yes, a new shell is started to replace your old one.

First, make a file like the C shell's .logout that will be read whenyour Bourne shell exits . (3.2) Save your tty (3.8) name in an environment variable (6.1), too-you'll need it later:

    trap
    TTY=`tty`; export TTY
    trap '. $HOME/.sh_logout; exit' 0

(Your system may need `$LOGDIR` instead of `$HOME`.) Put the following lines in your new .sh_logout file:

    exec <

    case

    exec -sh
    exec < $TTY
    echo "Do you really want to log out? \c"
    read ans
    case "$ans" in
    [Yy]*) ;;
    *)  exec $HOME/bin/-sh ;;
    esac

The last line is some trickery to start a new login shell (51.9). The shell closes your tty (45.20) before reading your .sh_logout file; the `exec < $TTY` reconnects the shell's standard input to your terminal.

Note that if your system is very slow, you may not get the reminder message for a couple of seconds-you might forget that it's coming and walk away. That hasn't been a problem where I've tested this. If it is for you though, replace the `read` `ans` with a program like grabchars (45.32) that times out and gives a default answer after a while. There may be some Bourne shells that need other tricks-and others that don't need these tricks-but this should give you an idea of what to do.

- JP

3.5 Stop Accidental C Shell Logouts |  | 3.7 Detaching a Session with screen