echo 1 > /sys/bus/pci/slots/$4/power bash: /sys/bus/pci/slots//power: Permission denied

Question

On typing echo 1 > /sys/bus/pci/slots/$4/power, I get this error:

bash: /sys/bus/pci/slots//power: Permission denied

Here is the output of lscpi -vvon my system:

02:00.0 Multimedia controller: Digital Devices GmbH Octopus DVB Adapter
        Subsystem: Digital Devices GmbH Cine S2 V6.5 DVB adapter
        Physical Slot: 4
        Flags: fast devsel, IRQ 46
        Memory at c7400000 (64-bit, non-prefetchable) [size=64K]
        Capabilities: [50] Power Management version 3
        Capabilities: [70] MSI: Enable+ Count=2/2 Maskable- 64bit+
        Capabilities: [90] Express Endpoint, MSI 00
        Capabilities: [100] Vendor Specific Information: ID=0000 Rev=0 Len=00c <?>
        Kernel driver in use: ddbridge

06:00.0 Multimedia controller: Digital Devices GmbH Max
        Subsystem: Digital Devices GmbH Max S8 4/8
        Physical Slot: 3
        Flags: fast devsel, IRQ 49
        Memory at c7300000 (64-bit, non-prefetchable) [size=64K]
        Capabilities: [50] Power Management version 3
        Capabilities: [70] MSI: Enable+ Count=2/2 Maskable- 64bit+
        Capabilities: [90] Express Endpoint, MSI 00
        Capabilities: [100] Vendor Specific Information: ID=0000 Rev=0 Len=00c <?>
        Kernel driver in use: ddbridge

Answer 1

echo won't work like that.

You would need use sudo tee instead like so to allow permission:

echo 1 | sudo tee /sys/bus/pci/slots/4/power

Also, I think you probably meant to specify slot 4 which would be 4 instead of $4.