Add "poll" watcher to batwatch

src/batwatch.sh

@@ -21,7 +21,7 @@ hook_pager
 # Watchers:
 # -----------------------------------------------------------------------------
 
-WATCHERS=("entr")
+WATCHERS=("entr" "poll")
 
 # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
 
@@ -46,6 +46,87 @@ watcher_entr_supported() {
 }
 
 
+# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
+
+POLL_STAT_VARIANT=''
+POLL_STAT_COMMAND=()
+
+determine_stat_variant() {
+	if [[ -n "$POLL_STAT_VARIANT" ]]; then
+		return 0
+	fi
+
+	# Try GNU stat.
+	if stat -c '%z' "$0" &>/dev/null; then
+		POLL_STAT_COMMAND=(stat -c '%z')
+		POLL_STAT_VARIANT='gnu'
+		return 0
+	fi
+
+	# Try BSD stat.
+	if stat -f '%m' "$0" &>/dev/null; then
+		POLL_STAT_COMMAND=(stat -f '%m')
+		POLL_STAT_VARIANT='bsd'
+		return 0
+	fi
+
+	return 1
+}
+
+watcher_poll_watch() {
+	determine_stat_variant
+
+	local files=("$@")
+	local times=()
+
+	# Get the initial modified times.
+	local file
+	local time
+	local modified=true
+	for file in "${files[@]}"; do
+		time="$("${POLL_STAT_COMMAND[@]}" "$file")"
+		times+=("$time")
+	done
+
+	# Display files.
+	while true; do
+		if "$modified"; then
+			modified=false
+
+			if [[ "$OPT_CLEAR" = "true" ]]; then
+				clear
+			fi
+	
+			"$BAT" "${BAT_ARGS[@]}" \
+				--terminal-width="$TERM_WIDTH" \
+				--paging=never \
+				"${files[@]}"
+		fi
+
+		local i=0
+		for file in "${files[@]}"; do
+			time="$("${POLL_STAT_COMMAND[@]}" "$file")"
+			
+			if [[ "$time" -ne "${times[$i]}" ]]; then
+				times[$i]="$time"
+				modified=true
+			fi
+
+			((i++))
+		done
+
+		sleep 1
+	done
+
+	"${POLL_STAT_COMMAND[@]}" "$@"
+	local ts
+}
+
+watcher_poll_supported() {
+	determine_stat_variant
+	return $?
+}
+
 # -----------------------------------------------------------------------------
 # Functions:
 # -----------------------------------------------------------------------------
@@ -132,11 +213,16 @@ if [[ -z "$OPT_WATCHER" ]]; then
 		printc "Please read the documentation at %{BLUE}%s%{CLEAR} for more details.\n" "$DOCS_URL/batwatch.md" 1>&2
 		exit 2
 	fi
-fi
+else
+	if ! type "watcher_${OPT_WATCHER}_supported" &>/dev/null; then
+		printc "%{RED}[%s error]%{CLEAR}: Unknown watcher: '%s'\n" "$PROGRAM" "$OPT_WATCHER" 1>&2
+		exit 1
+	fi
 
-if ! type "watcher_${OPT_WATCHER}_supported" &>/dev/null; then
-	printc "%{RED}[%s error]%{CLEAR}: Unknown watcher: '%s'\n" "$PROGRAM" "$OPT_WATCHER" 1>&2
-	exit 1
+	if ! "watcher_${OPT_WATCHER}_supported" &>/dev/null; then
+		printc "%{RED}[%s error]%{CLEAR}: Unsupported watcher: '%s'\n" "$PROGRAM" "$OPT_WATCHER" 1>&2
+		exit 1
+	fi
 fi
 
 # Run the main function.