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Is this Shell Interactive?

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

Alternatively, startup scripts may examine the variable PS1; it is unset in non-interactive shells, and set in interactive shells. Thus:

if [ -z "$PS1" ]; then
        echo This shell is not interactive
else
        echo This shell is interactive
fi

Copyright © 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
Licensed under the GNU Free Documentation License.
https://www.gnu.org/software/bash/manual/html_node/Is-this-Shell-Interactive_003f.html