parent child process

[simo_mon]

hi new to processes have a couple of questions ....


1 is main() 'the' initial parent process

ie when i call getppid() is that returning a reference to mains process ?*

2 when i call fork() is that the only time that a child process is created ?

3 how do you tell when a child process has ended

waitpid (), wait()..? and this causes the program to wait until it gets a signal

have done some reading and experimented with some code.... but still sketchy uderstanding ...



*apologies if this is a really stupid question

[Salem]

> 1 is main() 'the' initial parent process
main is what the C runtime library calls at the end of it's initialisation. It marks the start of your code.

void myfunc ( ) {
  printf( "hello world\n" );
}
int main ( ) {
  myfunc();
  return 0;
}

myfunc isn't a process any more than main is. A single process exists sometime before main is called until sometime after main returns. Everything in between is all the same process.


> ie when i call getppid() is that returning a reference to mains process ?
No, it's the ID of the thing which ran it.
If you double-clicked on an executable, then getpid() would be yourself, and getppid() would be explorer.

> 2 when i call fork() is that the only time that a child process is created ?
Yes (well, mostly).

> 3 how do you tell when a child process has ended
Those you've listed are good methods.
Or write a signal handler for SIGCHLD

[simo_mon]

thanks heaps totally cool and useful response...

that makes sense of a lot of the code behavior that i have been observing...

thanks again