This script creates wifi configuration for wpa_supplicant based on file SRC_FILE (by default /boot/wifi) or based on commandline arguments, then write it to WPA_SUPPLICANT_FILE (by default /etc/wpa_supplicant/wpa_supplicant.IFACE.conf) and apply changes.
SRC_FILE (if any) have to contain 1-3 lines:
SSID
password
country
If password is empty network considered unsecure.
Country can contain two symbols of country abbreviation, see https://en.wikipedia.org/wiki/ISO_3166-1_alpha-2
Country length truncated to two chars, so next chars if any are ignored. If country empty or invalid drop to 00 (World).
SRC_FILE if any will be removed after successful configuration.
The script can be added to /etc/rc.local to check SRC_FILE on every boot, or you may create separate systemd service for it.
It can be useful to setup wifi creds before OS booting by creation of file in /boot partition (which is FAT32 on Raspberry Pi, so the file can be created on Windows hosts easily).
From command line SRC_FILE can be set by:
set-wifi-creds -f SRC_FILE
Alternatively the script can be called this way (optional args are in []):
set-wifi-creds IFACE SSID [PW] [COUNTRY] [WPA_SUPPLICANT_FILE]
You may use empty strings '' if you don't want to set PW or COUNTRY but want to set WPA_SUPPLICANT_FILE.
Also IFACE, SRC_FILE, WPA_SUPPLICANT_FILE can be set as an environmental variables.