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.
Take our 
