Bash Check If Shell Is Interactive or Not Under Linux / Unix Oses

How do I check in GNU/Bash if a shell is running in interactive mode or not while writing shell scripts?

A bash shell is considered as an interactive shell when it reads and writes data from a user's terminal. Most startup scripts examine the shell variable called PS1. Usually, PS1 is set in interactive shells, and it is unset in non-interactive shells.

Find out if this shell interactive using PS1

The syntax is as follows:

// Is this Shell Interactive?
[ -z "$PS1" ] && echo "Noop" || echo "Yes"

OR

[ -z "$PS1" ] && echo "This shell is not interactive" || echo "This shell is interactive"

OR

[ -z "$PS1" ] && die "This script is not designed to run from $SHELL" 1 || do_interacive_shell_stuff

You can use bash shell if..else..fi syntax as follows:

 
if [ -z "$PS1" ]; then
       die "This script is not designed to run from $SHELL" 1
else
       //call our function
       do_interacive_shell_stuff
fi
 

From the bash reference manual

To determine within a startup script whether or not Bash is running interactively, test the value of the '-' special parameter. It contains i when the shell is interactive. For example:

 
case "$-" in
    *i*) echo "This shell is interactive" ;;
      *) echo "This shell is not interactive" ;;
esac
 

tty command

You can also use tty command as follows:

 
tty -s && echo "This shell is interactive" || echo "This shell is not interactive" ;;
 

OR

 
ssh user@server1.cyberciti.biz tty -s && echo "This shell is interactive" || echo "This shell is not interactive" ;;
 

References:

• GNU/Bourne-Again SHell manual

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