waiting for process in process substitution

[Brian J. Murrell]

I have a need to have a bash script communicate with another process, so
I start my other process using Process Substitution and echo commands to
it as such:

        exec 3> >(cat)
        echo "foo" >&3
        exec 3>&-
        exit

This is of course an oversimplification of what I'm doing but provides
for a very simple example.

The problem I'm running into is that the process that I am running in my
substitution can take a while to run and I want my main process to wait
for it to be done before it exits:

        exec 3> >(sleep_10; cat)
        /bin/echo "foo" >&3
        /bin/echo \004 >&3      # just to illustrate that the cat should exit 
here
        exec 3>&-
        # wait for cat to finish
        exit

Other than playing some trickery in the substitution sub-shell to create
a file and then remove it on start and spinning in the main process
while the file exists, I can't find a way to synchronize the two
processes.

So this works:

        exec 3> >(touch foo; sleep_10; cat; rm -f foo)
        /bin/echo "foo" >&3
        /bin/echo \004 >&3      # just to illustrate that the cat should exit 
here
        exec 3>&-
        while [ -f foo ]; do
            sleep 1
        done
        exit

But it's just so ugly.

For what it's worth, the process in the substitution is expect and what
I am feeding it from the script is an expect script.

Any ideas?

b.

-- 
My other computer is your Microsoft Windows server.

Brian J. Murrell

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