Add uniqify-recent

uniqify-recent

@@ -0,0 +1,52 @@
+#!/bin/bash
+if [[ $# -ge 1 && ( $# -gt 1 || ! "$1" =~ ^([0-9]|[1-9][0-9]*)(\.[0-9][0-9]*)?$ ) ]]; then
+	printf 'Usage: uniqify-recent [N]\n' >&2
+	printf 'After a line is read from stdin, its duplicates are suppressed for N seconds (default: 60)\n' >&2
+	printf 'N may have a fractional part, e.g. 123456.789\n' >&2
+	exit 1
+fi
+
+# EPOCHREALTIME was added in 4.4
+if (( BASH_VERSINFO[0] < 4 || ( BASH_VERSINFO[0] == 4 && BASH_VERSINFO[1] < 4 ) )); then
+	printf 'Error: this requires Bash 4.4 or higher\n' >&2
+	exit 1
+fi
+
+limit=60000000
+if [[ $# -eq 1 ]]; then
+	if [[ "$1" == *.* ]]; then
+		seconds="${1%.*}"
+		fraction="${1#*.}"
+	else
+		seconds="$1"
+		fraction=
+	fi
+	fraction="${fraction}000000"
+	fraction="${fraction:0:6}"
+	limit=$((seconds * 1000000 + fraction))
+fi
+
+# Bash 5.2 added ridiculousness in arithmetic context expansion of associative arrays. Revert that nonsense.
+if (( BASH_VERSINFO[0] > 5 || ( BASH_VERSINFO[0] == 5 && BASH_VERSINFO[1] >= 2 ) )); then
+	BASH_COMPAT=51
+fi
+
+declare -A lastseen
+lastclean=${EPOCHREALTIME/./}
+
+while IFS= read -r l; do
+	now=${EPOCHREALTIME/./}
+	if [[ ! -v 'lastseen[$l]' ]] || (( now - lastseen[\$l] > limit )); then
+		printf '%s\n' "$l"
+		lastseen["${l}"]="${now}"
+	fi
+	if (( now - lastclean > 10 * limit )); then
+		# Purge old entries
+		for k in "${!lastseen[@]}"; do
+			if (( now - lastseen[\$k] > limit )); then
+				unset -v 'lastseen[$k]'
+			fi
+		done
+		lastclean="${now}"
+	fi
+done