Shell Process Control R←{X}(8373⌶)Y

This function provides a way to determine the process IDs of processes started by ⎕SHELL, as well as enabling the sending of signals to any of those processes.

Monadic Use: Query Process IDs

If Y is a positive integer that identifies an APL thread number, and that thread is currently running ⎕SHELL, then R is the child process ID.

If Y is ⍬, then R is a numeric vector containing all the process IDs of the processes that remained running after ⎕SHELL completed (due to timeouts or interrupts for example - see ⎕SHELL for more information). Any call to 8373⌶ starts by removing the "dead" processes from the list; dead processes are ones that are no longer running but their ID is still reserved so that it is not reused by a different process.

Example

    tid←{
        ...
        r←⎕SHELL ...
        ...
    }&⍬

    processID←(8373⌶)tid
    processID
84093

Dyadic Use: Signal Child Process

X must be a integer scalar representing a signal number that is to be sent to the child process.

Y must be an integer scalar that identifies the child process:

• Positive values (including 0) are interpreted as APL thread numbers, and identify the child process of any currently running ⎕SHELL call on that thread.
• Negative values are negated and treated as process IDs. The process ID must be one of the processes left behind by a finished call to ⎕SHELL.

R is a Boolean scalar indicating whether the signal was successfully sent (1), as reported by the operating-system.