From f0dfaf5c06d8171b7a67843aec986b0b7c14b2d0 Mon Sep 17 00:00:00 2001
From: Matthias Kruk <m@m10k.eu>
Date: Thu, 15 Apr 2021 22:37:00 +0900
Subject: [PATCH] include/inst: Add inst module for managing running instances
 of scripts

This commit adds the inst module which provides functions for managing
instances of scripts:

 - The inst_start() function forks a function to the background
 - The inst_stop() function asks an instance to stop
 - The inst_list() function lists running instances
 - The inst_running() function tells an instance if it should stop

Internally, the module makes use of semaphores to list instances and
determine their state. Semaphores are kept in per-script directories
within $TOOLBOX_HOME/inst.
---
 include/inst.sh | 145 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 145 insertions(+)
 create mode 100644 include/inst.sh

diff --git a/include/inst.sh b/include/inst.sh
new file mode 100644
index 0000000..d20a8c5
--- /dev/null
+++ b/include/inst.sh
@@ -0,0 +1,145 @@
+#!/bin/bash
+
+__init() {
+	local name
+
+	name="${0##*/}"
+
+	if [[ -z "$name" ]]; then
+		echo "Could not determine script name" 1>&2
+		return 1
+	fi
+
+	if ! include "opt" "sem"; then
+		return 1
+	fi
+
+	declare -xgr __inst_name="$name"
+	declare -xgr __inst_path="$TOOLBOX_HOME/inst/$__inst_name"
+
+	if ! mkdir -p "$__inst_path"; then
+		return 1
+	fi
+
+	opt_add_arg "l" "list" "no"  0  "List running instances"  _inst_handle_opt
+	opt_add_arg "s" "stop" "yes" "" "Stop a running instance" _inst_handle_opt
+
+	return 0
+}
+
+_inst_handle_opt() {
+	local opt="$1"
+	local arg="$2"
+
+	local ret
+
+	ret=0
+
+	case "$opt" in
+		"stop")
+			if ! inst_stop "$arg"; then
+				ret=1
+			fi
+			;;
+
+		"list")
+			if ! inst_list; then
+				ret=1
+			fi
+			;;
+
+		*)
+			ret=1
+			;;
+	esac
+
+	exit "$ret"
+}
+
+inst_list() {
+	local sem
+
+	while read -r sem; do
+		local owner
+		local semval
+		local state
+		local argv
+
+		owner="${sem##*/}"
+		semval=$(sem_peek "$sem")
+
+		if ! argv=$(<"$sem.argv") 2> /dev/null; then
+			continue
+		fi
+
+		if (( semval > 0 )); then
+			state="STOPPING"
+		else
+			state="RUNNING"
+		fi
+
+		echo "$owner $state $__inst_name $argv"
+	done < <(find "$__inst_path" -regex ".*/[0-9]+")
+
+	return 0
+}
+
+inst_stop() {
+	local pid="$1"
+
+	local sem
+
+	sem="$__inst_path/$pid"
+
+	if ! sem_post "$sem"; then
+		return 1
+	fi
+
+	return 0
+}
+
+inst_running() {
+	if ! sem_trywait "$__inst_sem"; then
+		return 0
+	fi
+
+	return 1
+}
+
+_inst_run() {
+	local cmd="$1"
+	local args=("${@:2}")
+
+	local ret
+
+	declare -xgr __inst_sem="$__inst_path/$BASHPID"
+
+	if ! opt_get_argv > "$__inst_path/$BASHPID.argv"; then
+		log_error "Could not save args"
+		return 1
+	fi
+
+	if ! sem_init "$__inst_sem" 0; then
+		log_error "Could not initialize semaphore $__inst_sem"
+		return 1
+	fi
+
+	if ! "$cmd" "${args[@]}"; then
+		ret=1
+	else
+		ret=0
+	fi
+
+	if ! sem_destroy "$__inst_sem"; then
+		log_error "Could not destroy semaphore $__inst_sem"
+	fi
+
+	return "$ret"
+}
+
+inst_start() {
+	_inst_run "$@" </dev/null &>/dev/null &
+	disown
+
+	return 0
+}
-- 
2.47.3