How to check if option key is pressed at startup of a mac bash Application

Question

I got a relatively simple question.

I have a few mac applications that have launchers written in bash. I wanted to add a little feature to the launchers, by letting others access a config.app or something else located in /Contents/Resources, when they press the 'option/alt' key at the startup of the app. Kinda like iTunes or iPhoto, where you can access a little options menu.

I don't know how the code should look like when it's purely in bash; i found a few examples that make use of applescript and/or cocoa hooks, but none purely in bash.

Something like: if 'optionKeyDown'; then open "$WORKDIR/../Resources/config.app"

Or is this not possible in pure bash at all?

Answer 1

There's a good solution here: http://lists.apple.com/archives/applescript-users/2009/Sep/msg00374.html

Take the following code:

#import <Carbon/Carbon.h>

int main (int argc, const char * argv[]) {
    unsigned int modifiers = GetCurrentKeyModifiers();

    if (argc == 1)
        printf("%d\n", modifiers);

    else {

        int i, result = 1;
        for (i = 1; i < argc; ++i) {

            if (0 == strcmp(argv[i], "shift"))
                result = result && (modifiers & shiftKey);

            else if (0 == strcmp(argv[i], "option"))
                result = result && (modifiers & optionKey);

            else if (0 == strcmp(argv[i], "cmd"))
                result = result && (modifiers & cmdKey);

            else if (0 == strcmp(argv[i], "control"))
                result = result && (modifiers & controlKey);

            else if (0 == strcmp(argv[i], "capslock"))
                result = result && (modifiers & alphaLock);

        }
        printf("%d\n", result);
    }
    return 0;
}

Paste it into a file called, e.g. keys.m.

Then build a command line utility like this:

$ gcc keys.m -framework Carbon -o keys

Put the keys executable somewhere in your path, e.g. /usr/local/bin, or even just in the same directory as your bash script, then you can call it as e.g. keys option and check the returned string for "0" or "1".