check isatty in bash

Question

I want my shell to detect if human behavior, then show the prompt.

So, assume the file name is test.bash

#!/bin/bash
if [ "x" != "${PS1:-x}" ] ;then
 read -p "remove test.log Yes/No" x
 [ "$x" = "n" ] && exit 1
fi
rm -f test.log

But, I found it can not work if I haven't set PS1. Is there better method?

my test methods:

./test.bash                  # human interactive
./test.bash > /tmp/test.log  # stdout in batch mode
ls | ./test.bash             # stdin in batch mode

Answer 1

to elaborate, I would try

 if [ -t 0 ] ; then
    # this shell has a std-input, so we're not in batch mode 
   .....
 else
    # we're in batch mode

    ....
 fi

I hope this helps.

Answer 2

From help test:

 -t FD          True if FD is opened on a terminal.