Sstrhsrtj

I am trying to create a function that can run an arbitrary command, interact with the child process (specifics omitted), and then wait for it to exit. If successful, typing run <command> will appear to behave just like a bare <command>.

If I weren't interacting with the child process I would simply write:

run() {

    "$@"

}

But because I need to interact with it while it runs, I have this more complicated setup with coproc and wait.

run() {

    exec {in}<&0 {out}>&1 {err}>&2

    { coproc "$@" 0<&$in 1>&$out 2>&$err; } 2>/dev/null

    exec {in}<&- {out}>&- {err}>&-



    # while child running:

    #     status/signal/exchange data with child process



    wait

}

^{(This is a simplification. While the coproc and all the redirections aren't really doing anything useful here that "$@" & couldn't do, I need them all in my real program.)}

The "$@" command could be anything. The function I have works with run ls and run make and the like, but it fails when I do run vim. It fails, I presume, because Vim detects that it is a background process and doesn't have terminal access, so instead of popping up an edit window it suspends itself. I want to fix it so Vim behaves normally.

How can I make coproc "$@" run in the "foreground" and the parent shell become the "background"? The "interact with child" part neither reads from nor writes to the terminal, so I don't need it to run in the foreground. I'm happy to hand over control of the tty to the coprocess.

It is important for what I'm doing that run() be in the parent process and "$@" be in its child. I can't swap those roles. But I can swap the foreground and background. (I just don't know how to.)

Note that I am not looking for a Vim-specific solution. And I would prefer to avoid pseudo-ttys. My ideal solution would work equally well when stdin and stdout are connected to a tty, to pipes, or are redirected from files:

run echo foo                               # should print "foo"

echo foo | run sed 's/foo/bar/' | cat      # should print "bar"

run vim                                    # should open vim normally

Those three examples you gave should work if you add this line after wait:

jobs |grep -qi stopped && fg %1

So the script becomes:

run() {

    exec {in}<&0 {out}>&1 {err}>&2

    { coproc "$@" 0<&$in 1>&$out 2>&$err; } 2>/dev/null

    exec {in}<&- {out}>&- {err}>&-

    wait

    jobs |grep -qi stopped && fg %1

}

Though the %1 needs to change if you're running concurrent jobs. Then it gets more complicated because you then have to code identification of the job from the jobs output.