Piping into Shell scripts

[Conor P. Cahill]

In article <2283 at syma.sussex.ac.uk> andy at syma.sussex.ac.uk (Andy Clews) writes:
>Is there any way of getting a Shell script (C or Bourne) to recognise
>whether it is receiving input from a pipe?

tty(1) will report "not a tty" if it's input is not from a tty. 

So the following should work:

	testdata="`tty`"
	if [ "$testdata" = "not a tty" ]; then
		echo "we are not running from a terminal.  therefore we must"
		echo "be running from a pipe or with stdin redirected from a" 
		echo "file of some sort (of course, it also could be closed)"

		exit
	fi
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