How to run two multiple thread simultaneously in objective C?

I need to run two threads simultaneously, but I am not getting how to do so.

I start thread:

[NSThread detachNewThreadSelector:@selector开发者_如何学Python(MyNewThread:) toTarget:[CMyClass class] withObject:nil];    

-(void)MyNewThread:(id)param{
    NSAutoreleasePool *Pool = [[NSAutoreleasePool alloc] init];
    NSString *strSwitcher = @"myCommand";

    const char * cstrSwitcher = [strSwitcher UTF8String];
    system(cstrSwitcher);
    [Pool release];
}

and some other system command I want to send on other thread. When I send one system command prompt changes.(e.g. myCommand> ).

Now when I start another thread then that command only works when previous thread was stopped.

Anyone can help me??

By taking into account the info in your comment on the OP, I assume you want to call system() from multiple thread simultaneously.

Unfortunately, that cannot work because when you call system(), your application waits for a signal that is sent as soon as the child process exits. Because signals don't know anything about the threads in your application, system() cannot be run from multiple threads simultaneously.

Thanks for JeremyP to point into the direction of NSTask in the comments!

The alternative is to use the NSTask.

NSTask uses fork() to create a child process and calls waitpid() in the parent and execve() (or one of its siblings) in the child process. Using the macros defined in <sys/wait.h>, the child's return value is retrieved after it finishes. This way, multiple child process can be launched without blocking other threads. You can either do all that yourself, or just use the simple NSTask class.

I would suggest not using Hungarian notation (Windows picked that up back in the Win32 days, but dropped it in .NET) as that just complicates things. rename 'Pool' to 'pool', and 'strSwitcher' to 'switcher'. Now, just call system([switcher UTF8String]); instead of that extra variable. On top of this, remove the NSAutoreleasePool, and use the new @autoreleasepool { } definition, enclosing your code in it. Here's how it looks now.

- (void)myNewThread:(id)param {
    @autoreleasepool {
        NSString *switcher = @"myCommand";
        system([switcher UTF8String]);
    }
}

And if you'd like to switch to NSTasks to be able to run multiple executables, here's how it goes: (I also changed the method a bit.)

- (void)executeTaskAtPath:(NSString *)path withArguments:(NSArray *)arguments {
    @autoreleasepool {
        NSTask *task = [launchedTaskWithLaunchPath:path arguments:arguments];
        [task waitUntilExit]; // This blocks the thread.
    }
}

To find out if the task was terminated successfully, register for a NSTaskDidTerminateNotification at [NSNotificationCenter defaultCenter].