Cant disable WiFi power management Raspberry Pi 3 - raspberry-pi3

Question

Whenever i access sudo nano /etc/network/interfaces the file is essentially empty which is hindering me because i need to disable the power saving feature that automatically disables the wifi after a minute or so
This is what shows in my file
# interfaces(5) file used by ifup(8) and ifdown(8)
# Please note that this file is written to be used with dhcpcd
# For static IP, consult /etc/dhcpcd.conf and 'man dhcpcd.conf'
# Include files from /etc/network/interfaces.d:
source-directory /etc/network/interfaces.d
Because of this there is no where i can add the wireless-power off text and have it work.I have already tried to add this just at the bottom but it does not work.

Answer 1

Firstly you should repost this over at https://raspberrypi.stackexchange.com/
Secondly I am just facing the same issue, and solved it by entering this line into the crontab:
#reboot /sbin/iw dev wlan0 set power_save off&

Answer 2

I used the below to PERSISTENTLY kill WiFi Power Management across reboots. It's done as a systemd service so independent of how the network interfaces are configured and "just works".
Should work on any modern Pi which has systemd. Just copy & paste below bash script into a file, set it to executable and sudo ./fileName.sh:
if [ -d /root/scripts ]; then
mkdir /root/scripts
fi
apt-get -y install iw
apt-get -y install wireless-tools
cat <<EOF> /root/scripts/pwr-mgmnt-wifi-disable.sh
#!/bin/bash
iw dev wlan0 set power_save off
EOF
chmod 700 /root/scripts/pwr-mgmnt-wifi-disable.sh
cat <<EOF> /etc/systemd/system//pwr-mgmnt-wifi-disable.service
[Unit]
Description=Disable WiFi Power Management
Requires=network-online.target
After=hostapd.service
[Service]
User=root
Group=root
Type=oneshot
ExecStart=/root/scripts/pwr-mgmnt-wifi-disable.sh
[Install]
WantedBy=multi-user.target
EOF
chmod 644 /etc/systemd/system/pwr-mgmnt-wifi-disable.service
systemctl enable pwr-mgmnt-wifi-disable.service
systemctl start pwr-mgmnt-wifi-disable.service