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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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