Update install.sh

Reviewed-on: #9

install.sh

@@ -2,7 +2,7 @@
 
 set -e
 
-SCRIPT_URL="https://git.zakscode.com/ztimson/fallback-ap/raw/branch/master/fallback-ap.sh"
+SCRIPT_URL="https://git.zakscode.com/ztimson/fallback-ap/raw/branch/master/pi-fallback-ap.sh"
 INSTALL_PATH="/usr/local/bin/fallback-ap"
 
 if [ "$EUID" -ne 0 ]; then
@@ -13,17 +13,31 @@ fi
 
 prompt() {
     local __var="$1" __question="$2" __default="$3" __answer=""
-    if [ -e /dev/tty ]; then
-        read -r -p "$__question [$__default]: " __answer < /dev/tty || __answer=""
+    if exec 3<>/dev/tty 2>/dev/null; then
+        read -r -p "$__question [$__default]: " __answer <&3 || __answer=""
+        exec 3<&-
     fi
     printf -v "$__var" '%s' "${__answer:-$__default}"
 }
 
-[ -z "${FALLBACK_AP_SSID:-}" ]              && prompt FALLBACK_AP_SSID "Access point SSID" "$(hostname)"
-[ -z "${FALLBACK_AP_PASSWORD:-}" ]          && prompt FALLBACK_AP_PASSWORD "Access point passphrase" "abc123"
-[ -z "${FALLBACK_AP_CIDR:-}" ]              && prompt FALLBACK_AP_CIDR "Access point subnet (CIDR)" "10.10.10.1/24"
-[ -z "${FALLBACK_AP_DHCP_START_OCTET:-}" ]  && prompt FALLBACK_AP_DHCP_START_OCTET "DHCP range start (last octet)" "100"
-[ -z "${FALLBACK_AP_DHCP_END_OCTET:-}" ]    && prompt FALLBACK_AP_DHCP_END_OCTET "DHCP range end (last octet)" "250"
+EXISTING_CONFIG="/etc/fallback-ap.conf"
+
+if [ -f "$EXISTING_CONFIG" ]; then
+    # shellcheck disable=SC1090
+    source "$EXISTING_CONFIG"
+fi
+
+DEFAULT_SSID="${SAVED_SSID:-$(hostname)}"
+DEFAULT_PASSWORD="${SAVED_PASSWORD:-guesswhatitis}"
+DEFAULT_CIDR="${SAVED_CIDR:-10.10.10.1/24}"
+DEFAULT_DHCP_START_OCTET="${SAVED_DHCP_START_OCTET:-100}"
+DEFAULT_DHCP_END_OCTET="${SAVED_DHCP_END_OCTET:-250}"
+
+[ -z "${FALLBACK_AP_SSID:-}" ]              && prompt FALLBACK_AP_SSID "Access point SSID" "$DEFAULT_SSID"
+[ -z "${FALLBACK_AP_PASSWORD:-}" ]          && prompt FALLBACK_AP_PASSWORD "Access point passphrase" "$DEFAULT_PASSWORD"
+[ -z "${FALLBACK_AP_CIDR:-}" ]              && prompt FALLBACK_AP_CIDR "Access point subnet (CIDR)" "$DEFAULT_CIDR"
+[ -z "${FALLBACK_AP_DHCP_START_OCTET:-}" ]  && prompt FALLBACK_AP_DHCP_START_OCTET "DHCP range start (last octet)" "$DEFAULT_DHCP_START_OCTET"
+[ -z "${FALLBACK_AP_DHCP_END_OCTET:-}" ]    && prompt FALLBACK_AP_DHCP_END_OCTET "DHCP range end (last octet)" "$DEFAULT_DHCP_END_OCTET"
 
 export FALLBACK_AP_SSID FALLBACK_AP_PASSWORD FALLBACK_AP_CIDR FALLBACK_AP_DHCP_START_OCTET FALLBACK_AP_DHCP_END_OCTET