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Editorial Team
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Asked: 2026-06-16T15:09:39+00:00

I want to open one application instance only once, so I just do like

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I want to open one application instance only once, so I just do like
NSArray *apps = [NSRunningApplication runningApplicationsWithBundleIdentifier:@"com.my.app"]; in main.m
When I open the app from the console, the count of apps array will be 0. However, when I double click on the app, it will be 1
So can anyone tell me what’s the difference between the double click and console open? or give me another way to check if there’s already one instance running?

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1 Answer

  1. Editorial Team

    that command queries the workspace and that is updated ‘delayed’

    when the app is started from finder, it is launched via the NSWorkspace, so the workspace is updated right away

    when the app is started via the console/xcode it is not started via NSWorkspace, so that class returns 0 at the start. After the NSApplication of your process is up, the workspace is informed and its 1.

    => it is always correct in - (void)applicationDidFinishLaunching:(NSNotification *)aNotification

    so either wait for NSApplication to start and THEN kill it (like you do now, but later)

    OR

    see Preventing multiple process instances on Linux for a way to do it without cocoa

    OR

    you look at launchd which can do this 🙂 http://developer.apple.com/library/mac/#documentation/MacOSX/Conceptual/BPSystemStartup/Chapters/CreatingLaunchdJobs.html

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