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I'd like to autologin to tty1 on login and then use vlock to lock it.

How can I detect from Bash if the current terminal is a console virtual terminal (e.g. tty1), so that I can put the vlock line into .bash_profile and have it run only if logging in through tty1?

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  • 1
    I think you should change the title to "Detect if running in a virtual terminal" because tty can be misunderstood to mean detect if the current shell is connected to a pseudo-terminal device. Commented Oct 17, 2013 at 11:54
  • @JosephR. Thanks for pointing that out, fixed Commented Oct 17, 2013 at 11:58
  • @JosephR: bad call. A pseudo-terminal device is p ty, not tty. About to revert to original title. Commented Sep 9, 2015 at 12:07
  • Related: unix.stackexchange.com/questions/16387/… Commented Sep 9, 2015 at 12:18

2 Answers 2

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20

You can use tty to get the name of the current virtual terminal, then test against it with a case statement:

#!/bin/sh

case $(tty) in /dev/tty[0-9]*)
    vlock ;;
esac
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  • Even better, instead of assuming all terminal login shells are ttys. Commented Oct 17, 2013 at 11:38
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    No need to exclude X: if the script is running in a terminal emulator under X, tty will show the terminal emulator's pseudoterminal, not the physical terminal that X is running on. Commented Oct 17, 2013 at 21:54
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It is generally sufficient to simply test STDIN (FD0):

[ -t 0 ] && echo "TTY available" || echo "No TTY available"
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  • OK, because .bash_profile is called on login shells and the normal GUI login doesn't have a terminal, so the only terminal login shell should be a tty. Good find Commented Oct 17, 2013 at 11:07
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    If this snippet were included in a larger script that had its stdin redirected from a file, it would report that no TTY is available even if run from a VT. Commented Oct 17, 2013 at 11:59
  • 1
    @JosephR Correct. The value is often with cron or at jobs to avoid failures when scripts assume interactive input. Commented Oct 17, 2013 at 12:34

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