how to put a program into a .plan file

[david.e.wexelblat]

In article <1990Sep26.201406.12663 at athena.mit.edu>, jik at athena.mit.edu (Jonathan I. Kamens) writes:
> In article <978 at bbt.UUCP>, rgs at bbt.UUCP (steinbeiser) writes:
> |> Ok, how do you check the status of the file to see if it has
> |> been open by someone else?  Its not obvious how (or if) stat() would do this.
> |> Also, would the C program have to be running constantly in the background
> |> someplace?
> 
> 1. You open the pipe for write, and do a select() on it, and when you get an
>    OK to write from select(), you know that someone has opened the other end.
> 

Or, in System V, quoting from the open(2) man page:

	When opening a FIFO with O_RDONLY or O_WRONLY set:

	If O_NDELAY is set:
		[ not relevant ]

	If O_NDELAY is clear:
		An open for reading-only will block until a process
		opens the file for writing.  An open for writing-only
		will block until a process opens the file for reading.

So all you have to do is make .plan a FIFO, and have a program open
it for writing (the program will have to be in an infinite loop, though).

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
David Wexelblat             | dwex at mtgzx.att.com    | They recommended
AT&T Bell Laboratories      | ...!att!mtgzx!dwex    |    euthanasia
200 Laurel Ave - 4B-421     |                       | For nonconformists
Middletown, NJ  07748       | (201) 957-5871        |    everywhere