Checking the Current TTY

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# 11.5. Checking the Current TTY

The `tty` command returns the filename of the terminal connected to standard input. This comes in two formats on the Linux systems I have used, either "/dev/tty4" or "/dev/pts/2". I've used several methods over time, but the simplest I've found so far (probably both Linux- and Bash-2.x specific) is `temp=$(tty) ; echo ${temp:5}`. This removes the first five characters of the `tty` output, in this case "/dev/".

Previously, I used `tty | sed -e "s:/dev/::"`, which removes the leading "/dev/". Older systems (in my experience, RedHat through 5.2) returned only filenames in the "/dev/tty4" format, so I used `tty | sed -e "s/.*tty\(.*\)/\1/"`.

An alternative method: `ps ax | grep $$ | awk '{ print $2 }'`.

Relative speed: the ${temp:5} method takes about 0.12 seconds on an unloaded 486SX25, the sed-driven method takes about 0.19 seconds, the awk-driven method takes about 0.79 seconds.

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