Launch background process from unix command line and detect if it is runnin

Question

in Cocoa, I am able to run unix app by using NSTask, it works fine to me. But I want to do the following:
1. Start up a background process.
2. Wait to see if this background process has been launched correctly.
3. If yes, keep running following codes...
With NSTask, I cannot make sure when the background process has been launched correctly... and other codes just keep running...
If I do something like:
while (bgprocess isRunning)
}

Answer 1

What exactly do you mean by "launched correctly"? Do you just care that the process has begun? Do you want to make sure it is still running? Do you want to see if there is some signal emitted (either affirmative "I am running" or absence of a child-died signal)?
Your isRunning example does appear to be in accord with the NSTask docs for "do blah blah blah while the task is running", but that doesn't seem to be what your description says you want to do. Is "blah blah blah" an idle loop until the task has started, or is it something to do while the task is actually running?
How about looking up the pid of the child process (processIdentifier for the NSTask) and then check whether that process is still running?