Opening a macOS app from an unidentified developer.
Gatekeeper is a macOS application level security feature that aims to prevent unauthorized and unidentified apps from being launched, thereby preventing potential security problems like exploits or trojans from running on a Mac. The feature is most often encountered when an app has been downloaded from the web, and upon attempting to launch it, a warning dialog tells you that the application cannot be opened because it is from an unidentified developer. Blocked by the security system, the app does not start up.
The problem not only occurs with apps downloaded from the web, but may also occur if you modify an existing app by some other program. This is what arrived to me, when I changed the icons of my shell scripts to start and stop the Apache webserver using image2icon (cf. Changing application icons on macOS). The screenshot shows the message that popped up when I double-clicked the app in Applications and all you can do is pushing the OK button to close the message box.
One solution to make by app launchable per double-click from Applications and to avoid such issues in the future would be to disable Gatekeeper in Security System Preferences by allowing applications to be opened from Anywhere (instead of applications from App Store and from known developers only). Even though some websites say that Gatekeeper is really aimed at protecting novice and average Mac users, while advanced users, who are more comfortable with things, may find the warnings to be intrusive or annoying, I would not recommend to do so. First, this is a simple and efficient way to protect your Mac against malware code to be executed by running some third-party application. And second, it is very easy to launch an app from an unidentified developer: Just right-click the app and choose Open from the context menu. A warning message telling that macOS cannot verify the developer pops up. This seems the same as before, but there is a big difference: There is now an Open button available and when you push it, the app is launched.
And not only that: Opening it this way, the app is automatically added to a list of exceptions concerning application launching and the next time that you double-click the app in Applications, it opens as any "regular" app without that Gatekeeper displays a warning message (this might perhaps not work on older macOS versions...).
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