clean up battery code

niceties/battery.linux

@@ -1,6 +1,6 @@
 #!/bin/sh
 
 # this is a dirty hack.
-# acpi | awk '{print $4}' will print the battery percentage,
-# and s/,$// strips the trailing comma.
-acpi | awk '{print $4}' | sed 's/,$//'
+# acpi | awk '{print $4}' will print the battery percentage, stripping the
+# trailing comma
+acpi | awk '{sub(",$", "", $4); print $4}'

niceties/battery.netbsd

@@ -1,7 +1,10 @@
 #!/bin/sh
 
 envstat -s acpibat0:charge \
-	| sed 1,2d \
-	| cut -d ':' -f 2 \
-	| awk '{print $1}' \
-	| cut -d '.' -f 1
+	| awk '
+NR == 3 {
+	sub("^[^:]*:", "", $1);
+	sub(":.*", "", $1);
+	sub("\\..*", "", $1);
+	print $1;
+}'

niceties/batterymonitor

@@ -1,33 +1,31 @@
 #!/bin/sh
 
+set -e
+
 POLLING_FREQUENCY=1
 
-# ISO 8601
-alias date="date '+%Y-%m-%dT%T'"
 
-emit() {
-	printf "[%s] " "$(date)"
-	echo "$@"
-}
+alias date='printf "[%s] " "$(date +%Y-%m-%dT%T)"' # ISO 8601
 
 ! battery >/dev/null 2>&1 \
-	&& printf "Unable to get battery status on this system.\n" 1>&2 \
-	&& exit 1 \
-	|| true
+	&& ! printf "%s: Unable to get battery status on this system.\n" "$0" \
+		1>&2
 
-current_level=$(battery)
-previous_level=$current_level
+current_level="$(battery)"
+previous_level="$current_level"
 
-emit "$(printf "Current level: %d%%" "$current_level")"
+date; printf "Current level: %d%%\n" "$current_level"
 
 while true; do
-	current_level=$(battery)
-	if ! streq $current_level $previous_level; then
-		[ $current_level -lt $previous_level ] \
-			&& emit "$(printf "Discharged: %d%% -> %d%%\n" $previous_level $current_level )" \
-			|| emit "$(printf "   Charged: %d%% -> %d%%\n" $previous_level $current_level )"
+	current_level="$(battery)"
+	date; if ! streq "$current_level" "$previous_level"; then
+		printf '%s: %s%% -> %s%%\n' "$(
+			test "$current_level" -lt "$previous_level" \
+				&& printf 'Discharged' \
+				|| printf '   Charged')" \
+			"$previous_level" "$current_level"
 		previous_level=$current_level
 	fi
 
-	sleep $POLLING_FREQUENCY
+	sleep "$POLLING_FREQUENCY"
 done