You're right. The parent can just trap SIGCHLD and whatever "I'm done" signal the child is sending and sleep.

It's me again!

The kill function doesn't have to terminate another process. There are other signals that it can send. You can send several different signals to another process with it, such as:

$ kill -l
 1) SIGHUP       2) SIGINT       3) SIGQUIT      4) SIGILL
 5) SIGTRAP      6) SIGABRT      7) SIGEMT       8) SIGFPE
 9) SIGKILL     10) SIGBUS      11) SIGSEGV     12) SIGSYS
13) SIGPIPE     14) SIGALRM     15) SIGTERM     16) SIGURG
17) SIGSTOP     18) SIGTSTP     19) SIGCONT     20) SIGCHLD
21) SIGTTIN     22) SIGTTOU     23) SIGIO       24) SIGXCPU
25) SIGXFSZ     26) SIGVTALRM   27) SIGPROF     28) SIGWINCH
29) SIGLOST     30) SIGUSR1     31) SIGUSR2     32) SIGRTMAX
[download]

If both processes agree on a signal for communication, then you can put a signal handling function in your processes to receive the messages. For example, you could use SIGUSR1 to let P2 tell P1 that the text report is done. Then you could send SIGUSR2 to indicate that the spreadsheet is done.

I agree that communication between parent and child to be established via the signals provided and that would prove to be more robust and synchronous instead of communication being asynchronous when its not needed.

:)