Simple bash script parallelization using semaphores

semlock.sh

#!/bin/bash

SEMPATH="/tmp"
SEMNAME=""

semtake() {
	local name="$1"
	[ -z "$name" ] && echo "Missing semaphore name!" && return 1
	local j="$2"
	[ -z "$2" ] && j=$(nproc)
	[ -n "$SEMNAME" ] && echo "Already have $SEMNAME" && return 1
	while true; do
		for i in $(seq 1 $j); do
			SEMNAME=".semlock-$name-$j-$i"
			mkdir "$SEMPATH/$SEMNAME" 2>/dev/null && break 2
		done
		sleep 1
	done
	trap semgive EXIT
}

semgive() {
	[ -z "$SEMNAME" ] && return
	rmdir "$SEMPATH/$SEMNAME" &>/dev/null || true
	SEMNAME=""
}

semnotify.sh

#!/bin/bash

[ -z "$(command -v inotifywait)" ] && echo "inotify-tools need to be installed for $0 to work!" >&2 && return 1

SEMPATH="/tmp"
[ ! -d "$SEMPATH" ] && echo "$SEMPATH is not a valid directory" >&2 && return 1

! (return 0 2>/dev/null) && echo "$0 can only be sourced, not executed" >&2 && exit 1

#SEMNAME=""
#SEMNAMEID=""

semtake_pool() {
	local SEMNAME="$1"
	local j="$2"
	for i in $(seq 1 "$j"); do
		SEMNAMEID="$i"
		mkdir "$SEMPATH/$SEMNAME-$SEMNAMEID" 2>/dev/null || continue
		return 0
	done
	unset SEMNAMEID
	return 1
}

semtake() {
	local name="$1"
	[ -z "$name" ] && echo "Missing semaphore name!" >&2 && return 1
	local j="$2"
	[ -z "$2" ] && j=$(nproc)
	[ -n "$SEMNAMEID" ] && echo "Already have $SEMNAME" >&2 && return 1
	SEMNAME=".semlock-$name"
	until semtake_pool "$SEMNAME" "$j"; do
		local i
		i="$(find "$SEMPATH" -maxdepth 1 -type d -name "$SEMNAME-wait-*" 2>/dev/null | sed 's/^.*-\([[:digit:]]*\)$/\1/' | sort -n | tail -1)"
		[ -z "$i" ] && i=0
		local SEMWAITNAME
		while true; do
			SEMWAITNAME="$SEMNAME"-wait-$i
			i=$((i+1))
			mkdir "$SEMPATH"/"$SEMWAITNAME" &>/dev/null || continue
			break
		done
		inotifywait --quiet --quiet --event delete_self "$SEMPATH"/"$SEMWAITNAME"
		rmdir "$SEMPATH"/"$SEMWAITNAME" &>/dev/null || true
	done
	trap semgive EXIT
}

semgive() {
	[ -z "$SEMNAME" ] && return
	[ -z "$SEMNAMEID" ] && return
	rmdir "$SEMPATH"/"$SEMNAME"-"$SEMNAMEID" &>/dev/null || true
	unset SEMNAMEID
	local i
	i="$(find "$SEMPATH" -maxdepth 1 -type d -name "$SEMNAME-wait-*" 2>/dev/null | sed 's/^.*-\([[:digit:]]*\)$/\1/' | sort -n | head -1)"
	[ -z "$i" ] && return
	local SEMWAITNAME
	local waiter
	for waiter in "$SEMPATH"/"$SEMNAME"-wait-*; do
		SEMWAITNAME="$SEMNAME"-wait-$i
		i=$((i+1))
		rmdir "$SEMPATH"/"$SEMWAITNAME" &>/dev/null || continue
		break
	done
	unset SEMNAME
}

Reserved