akorn/runcached

## runcached
#!/bin/zsh
#
# Purpose: run speficied command with specified arguments and cache result. If cache is fresh enough, don't run command again but return cached output.
# Also cache exit status and stderr.

# Use silly long variable names to avoid clashing with whatever the invoked program might use
RUNCACHED_MAX_AGE=300
RUNCACHED_CACHE_DIR=/var/cache/runcached
RUNCACHED_IGNORE_ENV=0
RUNCACHED_IGNORE_PWD=0
[[ -n "$HOME" ]] && RUNCACHED_CACHE_DIR=$HOME/.runcached

function usage() {
	echo "Usage: runcached [--ttl <max cache age>] [--cache-dir <cache directory>]"
	echo "		 [--ignore-env] [--ignore-pwd] [--help] [--prune-cache]"
	echo "                 [--] command [arg1 [arg2 ...]]"
	echo
	echo
	echo "Run 'command' with the specified args and cache stdout, stderr and exit"
	echo "status. If you run the same command again and the cache is fresh, cached"
	echo "data is returned and the command is not actually run. Side effects of"
	echo "'command' are not cached."
	echo
	echo "Normally, all environment variables as well as the current working directory"
	echo "are included in the cache key. The --ignore options disable this. The OLDPWD"
	echo "variable is always ignored."
	echo
	echo "--prune-cache deletes all cache entries older than the maximum age. There is"
	echo "no other mechanism to prevent the cache growing without bounds."
	echo
	echo "Note that there is no cache invalidation logic except cache age"
	echo "(specified in seconds)."
	echo
	echo "The default cache directory is ${RUNCACHED_CACHE_DIR}."
	echo "Maximum cache age defaults to ${RUNCACHED_MAX_AGE}."
	echo
	echo "If the cache can't be created, the command is run uncached."
	echo "This script is always silent; any output comes from the invoked command."
	exit 0
}

while [[ -n "$1" ]]; do
	case "$1" in
		--ttl)		RUNCACHED_MAX_AGE="$2"; shift 2;;
		--cache-dir)	RUNCACHED_CACHE_DIR="$2"; shift 2;;
		--ignore-env)	RUNCACHED_IGNORE_ENV=1; shift;;
		--ignore-pwd)	RUNCACHED_IGNORE_PWD=1; shift;;
		--prune-cache)	RUNCACHED_PRUNE=1; shift;;
		--help)		usage;;
		--)		shift; break;;
		*)		break;;
	esac
done

zmodload zsh/datetime
zmodload zsh/stat

[[ -d "$RUNCACHED_CACHE_DIR" ]] || mkdir -p "$RUNCACHED_CACHE_DIR" >/dev/null 2>/dev/null

((RUNCACHED_PRUNE)) && find "$RUNCACHED_CACHE_DIR/." -maxdepth 1 -type f \! -newermt @$[EPOCHSECONDS-RUNCACHED_MAX_AGE] -delete 2>/dev/null

(
	unset OLDPWD	# Almost(?) nothing uses OLDPWD, but taking it into account potentially reduces cache efficency.
	((RUNCACHED_IGNORE_PWD)) && unset PWD
	((RUNCACHED_IGNORE_ENV)) || env
	echo -E "$@"
) | md5sum | read RUNCACHED_CACHE_KEY RUNCACHED__crap__

{{RUNCACHED_LOCK_FD}}>>$RUNCACHED_CACHE_DIR/$RUNCACHED_CACHE_KEY.lock

# If we can't obtain a lock, we want to run uncached; otherwise
# 'runcached' wouldn't be transparent because it would prevent
# parallel execution of several instances of the same command.
# Locking is necessary to avoid races between the mv(1) command
# below replacing stderr with a newer version and another instance
# of runcached using a newer stdout with the older stderr.
if flock -n $RUNCACHED_LOCK_FD 2>/dev/null; then
	if [[ -f $RUNCACHED_CACHE_DIR/$RUNCACHED_CACHE_KEY.stdout ]]; then
		if [[ $[EPOCHSECONDS-$(zstat +mtime $RUNCACHED_CACHE_DIR/$RUNCACHED_CACHE_KEY.stdout)] -le $RUNCACHED_MAX_AGE ]]; then
			cat $RUNCACHED_CACHE_DIR/$RUNCACHED_CACHE_KEY.stdout &
			cat $RUNCACHED_CACHE_DIR/$RUNCACHED_CACHE_KEY.stderr >&2 &
			wait
			exit $(<$RUNCACHED_CACHE_DIR/$RUNCACHED_CACHE_KEY.exitstatus)
		else
			rm -f $RUNCACHED_CACHE_DIR/$RUNCACHED_CACHE_KEY.{stdout,stderr,exitstatus} 2>/dev/null
		fi
	fi

	# only reached if cache didn't exist or was too old
	if [[ -d $RUNCACHED_CACHE_DIR/. ]]; then
		RUNCACHED_tempdir=$(mktemp -d 2>/dev/null)
		if [[ -d $RUNCACHED_tempdir/. ]]; then
			$@ >&1 >$RUNCACHED_tempdir/$RUNCACHED_CACHE_KEY.stdout 2>&2 2>$RUNCACHED_tempdir/$RUNCACHED_CACHE_KEY.stderr
			RUNCACHED_ret=$?
			echo $RUNCACHED_ret >$RUNCACHED_tempdir/$RUNCACHED_CACHE_KEY.exitstatus 2>/dev/null
			mv $RUNCACHED_tempdir/$RUNCACHED_CACHE_KEY.{stdout,stderr,exitstatus} $RUNCACHED_CACHE_DIR/ 2>/dev/null
			rmdir $RUNCACHED_tempdir 2>/dev/null
			exit $RUNCACHED_ret
		fi
	fi
fi

# only reached if cache not created successfully or lock couldn't be obtained
exec $@
	#!/bin/zsh
	#
	# Purpose: run speficied command with specified arguments and cache result. If cache is fresh enough, don't run command again but return cached output.
	# Also cache exit status and stderr.

	# Use silly long variable names to avoid clashing with whatever the invoked program might use
	RUNCACHED_MAX_AGE=300
	RUNCACHED_CACHE_DIR=/var/cache/runcached
	RUNCACHED_IGNORE_ENV=0
	RUNCACHED_IGNORE_PWD=0
	[[ -n "$HOME" ]] && RUNCACHED_CACHE_DIR=$HOME/.runcached

	function usage() {
	echo "Usage: runcached [--ttl <max cache age>] [--cache-dir <cache directory>]"
	echo " [--ignore-env] [--ignore-pwd] [--help] [--prune-cache]"
	echo " [--] command [arg1 [arg2 ...]]"
	echo
	echo
	echo "Run 'command' with the specified args and cache stdout, stderr and exit"
	echo "status. If you run the same command again and the cache is fresh, cached"
	echo "data is returned and the command is not actually run. Side effects of"
	echo "'command' are not cached."
	echo
	echo "Normally, all environment variables as well as the current working directory"
	echo "are included in the cache key. The --ignore options disable this. The OLDPWD"
	echo "variable is always ignored."
	echo
	echo "--prune-cache deletes all cache entries older than the maximum age. There is"
	echo "no other mechanism to prevent the cache growing without bounds."
	echo
	echo "Note that there is no cache invalidation logic except cache age"
	echo "(specified in seconds)."
	echo
	echo "The default cache directory is ${RUNCACHED_CACHE_DIR}."
	echo "Maximum cache age defaults to ${RUNCACHED_MAX_AGE}."
	echo
	echo "If the cache can't be created, the command is run uncached."
	echo "This script is always silent; any output comes from the invoked command."
	exit 0
	}

	while [[ -n "$1" ]]; do
	case "$1" in
	--ttl) RUNCACHED_MAX_AGE="$2"; shift 2;;
	--cache-dir) RUNCACHED_CACHE_DIR="$2"; shift 2;;
	--ignore-env) RUNCACHED_IGNORE_ENV=1; shift;;
	--ignore-pwd) RUNCACHED_IGNORE_PWD=1; shift;;
	--prune-cache) RUNCACHED_PRUNE=1; shift;;
	--help) usage;;
	--) shift; break;;
	*) break;;
	esac
	done

	zmodload zsh/datetime
	zmodload zsh/stat

	[[ -d "$RUNCACHED_CACHE_DIR" ]] \|\| mkdir -p "$RUNCACHED_CACHE_DIR" >/dev/null 2>/dev/null

	((RUNCACHED_PRUNE)) && find "$RUNCACHED_CACHE_DIR/." -maxdepth 1 -type f \! -newermt @$[EPOCHSECONDS-RUNCACHED_MAX_AGE] -delete 2>/dev/null

	(
	unset OLDPWD # Almost(?) nothing uses OLDPWD, but taking it into account potentially reduces cache efficency.
	((RUNCACHED_IGNORE_PWD)) && unset PWD
	((RUNCACHED_IGNORE_ENV)) \|\| env
	echo -E "$@"
	) \| md5sum \| read RUNCACHED_CACHE_KEY RUNCACHED__crap__

	{{RUNCACHED_LOCK_FD}}>>$RUNCACHED_CACHE_DIR/$RUNCACHED_CACHE_KEY.lock

	# If we can't obtain a lock, we want to run uncached; otherwise
	# 'runcached' wouldn't be transparent because it would prevent
	# parallel execution of several instances of the same command.
	# Locking is necessary to avoid races between the mv(1) command
	# below replacing stderr with a newer version and another instance
	# of runcached using a newer stdout with the older stderr.
	if flock -n $RUNCACHED_LOCK_FD 2>/dev/null; then
	if [[ -f $RUNCACHED_CACHE_DIR/$RUNCACHED_CACHE_KEY.stdout ]]; then
	if [[ $[EPOCHSECONDS-$(zstat +mtime $RUNCACHED_CACHE_DIR/$RUNCACHED_CACHE_KEY.stdout)] -le $RUNCACHED_MAX_AGE ]]; then
	cat $RUNCACHED_CACHE_DIR/$RUNCACHED_CACHE_KEY.stdout &
	cat $RUNCACHED_CACHE_DIR/$RUNCACHED_CACHE_KEY.stderr >&2 &
	wait
	exit $(<$RUNCACHED_CACHE_DIR/$RUNCACHED_CACHE_KEY.exitstatus)
	else
	rm -f $RUNCACHED_CACHE_DIR/$RUNCACHED_CACHE_KEY.{stdout,stderr,exitstatus} 2>/dev/null
	fi
	fi

	# only reached if cache didn't exist or was too old
	if [[ -d $RUNCACHED_CACHE_DIR/. ]]; then
	RUNCACHED_tempdir=$(mktemp -d 2>/dev/null)
	if [[ -d $RUNCACHED_tempdir/. ]]; then
	$@ >&1 >$RUNCACHED_tempdir/$RUNCACHED_CACHE_KEY.stdout 2>&2 2>$RUNCACHED_tempdir/$RUNCACHED_CACHE_KEY.stderr
	RUNCACHED_ret=$?
	echo $RUNCACHED_ret >$RUNCACHED_tempdir/$RUNCACHED_CACHE_KEY.exitstatus 2>/dev/null
	mv $RUNCACHED_tempdir/$RUNCACHED_CACHE_KEY.{stdout,stderr,exitstatus} $RUNCACHED_CACHE_DIR/ 2>/dev/null
	rmdir $RUNCACHED_tempdir 2>/dev/null
	exit $RUNCACHED_ret
	fi
	fi
	fi

	# only reached if cache not created successfully or lock couldn't be obtained
	exec $@