Relaunching a cocoa app - objective-c

Question

I have an application that checks its command line parameters and stores values in persistent stores. One of those is a password that I don't want sticking around for people to see with 'ps' and friends. The approach I'm currently looking at is to, after I've stored the values I need, relaunch the process without the command line parameters. My naive approach is this, where args[0] is the path to the application:
NSTask *task = [[NSTask alloc] init];
[task setLaunchPath:[args objectAtIndex:0]];
[task launch];
[task release];
[NSApp terminate:nil];
The child is run. However, when my app is terminated the child doesn't seem to orphan but gets stuck. Am I just way off on this one?
More info: So it seems that when I call [NSApp terminate:nil] the NSTask that was launched gets stuck, but if I just exit() then it works fine. However, I'm concerned that things that are open (keychain, plist, etc.) will be in a bad state if I do that.
And note that lots of example code out there is about some watchdog-like process that restarts a separate process when needed. I'm trying to restart the current process that's already running from within that same process.

Answer 1

There are plenty of examples on the web, but this one (also below) looks like it has all the code you need. There are more detailed explanations out there, as well.
// gcc -Wall -arch i386 -arch ppc -mmacosx-version-min=10.4 -Os -framework AppKit -o relaunch relaunch.m
#import <AppKit/AppKit.h>
#interface TerminationListener : NSObject
{
const char *executablePath;
pid_t parentProcessId;
}
- (void) relaunch;
#end
#implementation TerminationListener
- (id) initWithExecutablePath:(const char *)execPath parentProcessId:(pid_t)ppid
{
self = [super init];
if (self != nil) {
executablePath = execPath;
parentProcessId = ppid;
// This adds the input source required by the run loop
[[[NSWorkspace sharedWorkspace] notificationCenter] addObserver:self selector:#selector(applicationDidTerminate:) name:NSWorkspaceDidTerminateApplicationNotification object:nil];
if (getppid() == 1) {
// ppid is launchd (1) => parent terminated already
[self relaunch];
}
}
return self;
}
- (void) applicationDidTerminate:(NSNotification *)notification
{
if (parentProcessId == [[[notification userInfo] valueForKey:#"NSApplicationProcessIdentifier"] intValue]) {
// parent just terminated
[self relaunch];
}
}
- (void) relaunch
{
[[NSWorkspace sharedWorkspace] launchApplication:[NSString stringWithUTF8String:executablePath]];
exit(0);
}
#end
int main (int argc, const char * argv[])
{
if (argc != 3) return EXIT_FAILURE;
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
[[[TerminationListener alloc] initWithExecutablePath:argv[1] parentProcessId:atoi(argv[2])] autorelease];
[[NSApplication sharedApplication] run];
[pool release];
return EXIT_SUCCESS;
}

Answer 2

I know its a bit late to answer but this answer may help others. Here is a cool trick that can help you.
By using the terminal command, just open your application as a new instance and terminate the current instance.
This is how it is done:
....
NSString* path = [[NSBundle mainBundle] bundlePath];
NSString* cmd = [NSString stringWithFormat:#"open -n %#", path];
[self runCommand:cmd];
exit(0);
}
/// temrinal function
-(NSString*)runCommand:(NSString*)commandToRun;
{
NSTask *task;
task = [[NSTask alloc] init];
[task setLaunchPath: #"/bin/sh"];
NSArray *arguments = [NSArray arrayWithObjects:
#"-c" ,
[NSString stringWithFormat:#"%#", commandToRun],
nil];
NSLog(#"run command: %#",commandToRun);
[task setArguments: arguments];
NSPipe *pipe;
pipe = [NSPipe pipe];
[task setStandardOutput: pipe];
NSFileHandle *file;
file = [pipe fileHandleForReading];
[task launch];
NSData *data;
data = [file readDataToEndOfFile];
NSString *output;
output = [[NSString alloc] initWithData: data encoding: NSUTF8StringEncoding];
return output;
}

Answer 3

Create an external process that launches yours when it terminates. Then terminate. Launching Cocoa programs with NSTask doesn't work quite right.

Answer 4

For anyone who still wants to use NSTask to relaunch,I found one possible way: Please DO NOT set NSPipe of the NSTask,because the NSTask will terminate the app itself,once the app terminated,the NSTask that started might get stuck there.
At least for me,after I removed the NSPipe settings,my app relaunch successfully.
The following is what I do:
1. Write a command line tool which has 3 parameters: app bundle id,app full path,please note that in this command line you need to terminate the app and wait for a while to make sure it is really terminated before launch the new one,I keep checking app.isTerminated and sleep(1) if it's not terminated.
Launch the Command line tool in app using NSTask,and set the parameters accorddingly,Don't use NSPipe,simply create NSTask and launch
The app relaunches now