Bash: detect execute vs source in a script?

I have a script that is littered around my filesystem (side effect of a build process) that sets some global environment variables (LD_LIBRARY_PATH, PATH, ROOTDIR, etc) that need to be in my shell for proper operation. Of course, that means I need to source script.sh or . script.sh to get it to work, and not ./script.sh (which would spawn a new shell and not set the variables in my current shell).

Is there anything I can add to the script to prevent (or warn) someone running ./script.sh ?

Solution 1:

In a shell script, $0 is the name of the currently running script. You can use this to tell if you're being sourced or run like this:

if [[ "$(basename -- "$0")" == "script.sh" ]]; then
    echo "Don't run $0, source it" >&2
    exit 1
fi

Solution 2:

Simplest way in bash is:

if [ "$0" = "$BASH_SOURCE" ]; then
    echo "Error: Script must be sourced"
    exit 1
fi

$BASH_SOURCE always contains the name/path of the script.

$0 only contains the name/path of the script when NOT sourced.

So when they match, that means the script was NOT sourced.

Solution 3:

This has been discussed on SO. The most-upvoted answer by @barroyo says to use

[[ "${BASH_SOURCE[0]}" != "${0}" ]] && echo "script ${BASH_SOURCE[0]} is being sourced ..."

Solution 4:

Another option may be to remove execute permissions. In that case it can not be executed but it can still be sourced.