6.3.1 What is an Interactive Shell?
An interactive shell is one started without non-option arguments, unless -s is specified, without specifying the -c option, and whose input and error output are both connected to terminals (as determined by isatty(3)), or one started with the -i option.
An interactive shell generally reads from and writes to a user’s terminal.
The -s invocation option may be used to set the positional parameters when an interactive shell is started.
6.3.2 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:
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case "$-" in
-
*i*) echo This shell is interactive ;;
-
*) echo This shell is not interactive ;;
- esac
Alternatively, startup scripts may examine the variable PS1; it is unset in non-interactive shells, and set in interactive shells. Thus:
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if [ -z "$PS1" ]; then
-
echo This shell is not interactive
-
else
-
echo This shell is interactive
- fi