ignore output of program - flush directly to terminal

[J-Cake]

Discussed in #11471

^{Originally posted by J-Cake January 2, 2024}
Hey, when set up, qemu can connect its stdio to a TTY on guest. This is epic because it allows you to interact with the guest via a standard terminal much like how SSH would. However, (my understanding) nushell attempts to parse the output in some way, and buffers it. This causes the output of Qemu to freeze until the process exists. At this point the buffer is flushed and I see everything. I'm hoping to instruct nushell to just leave it be for this one command so I don't have to drop back to bash. Any tips?

---

My QEMU command is:

def main [
    --bios: path = "/usr/share/OVMF/OVMF_CODE.fd",
    --drive: path = "*redox*.qcow2"
    --mem: int = 8,
    --cpu_cores: int = 8,
] {
    (
        qemu-system-x86_64
            --enable-kvm
            --name "Redox OS"
            --machine q35
            # --display egl-headless,rendernode=/dev/dri/card0,
            --display sdl
            -k de

            -m $"($mem)G" #Mem

            -cpu host -smp $cpu_cores #CPU

            # -drive $"if=pflash,format=raw,readonly=on,file=($bios)" # Bios

            -blockdev $"qcow2,node-name=nvme0,file.driver=file,file.filename=(glob $drive | first)" # Storage File
            -device nvme,drive=nvme0,serial=deadbeef1 # Storage Controller

            -device virtio-gpu-pci # Display

            -device virtio-net,netdev=net0 -netdev user,id=net0 # Network

            -device nec-usb-xhci,id=xhci # USB

            -chardev stdio,id=debug,signal=on,mux=on # TTY
            -serial chardev:debug # Debug
            --mon chardev=debug # Monitor

    )
}

The BASH code I translated from it is

qemu-system-x86_64 --enable-kvm --name "Redox OS" --machine q35 --display sdl -k de -m 8G -cpu host -smp 8 \
    -blockdev qcow2,node-name=nvme0,file.driver=file,file.filename=/home/jcake/Erika/redox.qcow2 \
     -device nvme,drive=nvme0,serial=deadbeef1 \
     -device virtio-gpu-pci \
     -device virtio-net,netdev=net0 -netdev user,id=net0 \
     -device nec-usb-xhci,id=xhci \
     -chardev stdio,id=debug,signal=off,mux=on -serial chardev:debug \
     --mon chardev=debug

Accounting for manual variable substitution, the two commands are identical. One works in Bash, and the other doesn't work in nushell...

I'm promoting this to an issue since I get the impression this is not desired behaviour. I'm still struggling with this issue and would sincerely appreciate help

[fdncred]

I don't use qemu so it's hard to tell. I'm guessing it could be something with how nushell communicates on stdout with the pipeline.

[nibon7]

What's your nushell version? @J-Cake

I don't see any difference between bash and nushell with these options -chardev stdio,id=debug,signal=off,mux=on -serial chardev:debug --mon chardev=debug.

[J-Cake]

What's your nushell version? @J-Cake

I don't see any difference between bash and nushell with these options -chardev stdio,id=debug,signal=off,mux=on -serial chardev:debug --mon chardev=debug.

Yep. That's precisely my point. There isn't a difference. Therefore it must be an issue with nushell. Conveniently, I'm at work at the moment, and likely won't be home until much later, but I'll let you know as soon as I can. Cheers

[nibon7]

Both bash and nushell work well on my pc.

qemu-system-x86_64 \
--enable-kvm \
-cpu host \
-machine pc \
-kernel vmlinuz-6.7.0 \
-initrd initrd.zst \
-append 'console=ttyS0 loglevel=8 root=/dev/ram0' \
-chardev stdio,id=debug,signal=off,mux=on \
-serial chardev:debug \
--mon chardev=debug

[J-Cake]

That is very curious... It consistently doesn't work on mine...