Question

I would like to test in my bash script where stdout and stderr are directed, or more precisely, if they have been redirected.

Have you an idea ?

The $* bash variable don’t give me this info.

Answer 1

You should be able to use the -t test switch to tell if the output streams are ttys or not:

if [ -t 1 ] ; then
  echo stdout is a terminal
else
  echo stdout is not a terminal
fi

Use -t 0 for stdin.

Use -t 2 for stderr.