Objective-C command line tool

main.m

@import Foundation;

int main(int argc, const char * argv[])
{
    __block BOOL keepRunning = YES;
    
    // Configure a dispatch source to listen for SIGTERM
    // Adapted from https://mikeash.com/pyblog/friday-qa-2011-04-01-signal-handling.html
    dispatch_source_t source = dispatch_source_create(DISPATCH_SOURCE_TYPE_SIGNAL, SIGTERM, 0, dispatch_get_main_queue());
    dispatch_source_set_event_handler(source, ^{
        printf("SIGTERM received!\n");
        keepRunning = NO;
    });
    dispatch_resume(source);
    
    // Tell sigaction to ignore SIGTERM - it's handled by the dispatch source above
    struct sigaction action = {0};
    action.sa_handler = SIG_IGN;
    sigaction(SIGTERM, &action, NULL);
    
    // Main run loop
    @autoreleasepool {
        NSLog(@"Hello, world!");
        
        NSRunLoop *runLoop = [NSRunLoop currentRunLoop];
        do {
            @autoreleasepool {
                [runLoop runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];
            }
        } while (keepRunning);
    }
    
    return 0;
}

Because of the dispatch source, we don’t have to resort to the hacky “add a port to the run loop” fix to prevent the main loop from spinning out of control.