Можно использовать в (1) команда в сценарии для планирования его следующего запуска. Прежде чем это выйдет, это может проверить myhappyschedule в течение времени следующего запуска. Вам не нужен крон вообще, действительно.

I came across this question while researching for a solution to the queuing problem. For the benefit of anyone else searching here is my solution.

Combine this with a cron that starts jobs as they are scheduled (even if they are scheduled to run at the same time) and that solves the problem you described as well.

Problem

• At most one instance of the script should be running.
• We want to cue up requests to process them as fast as possible.

ie. We need a pipeline to the script.

Solution:

Create a pipeline to any script. Done using a small bash script (further down).

The script can be called as
./pipeline ""

Example:

./pipeline sleep 10 &
./pipeline shabugabu &
./pipeline single_instance_script some arguments &
./pipeline single_instance_script some other_argumnts &
./pipeline "single_instance_script some yet_other_arguments > output.txt" &
..etc

The script creates a new named pipe for each command. So the above will create named pipes: sleep, shabugabu, and single_instance_script

In this case the initial call will start a reader and run single_instance_script with some arguments as arguments. Once the call completes, the reader will grab the next request off the pipe and execute with some other_arguments, complete, grab the next etc...

This script will block requesting processes so call it as a background job (& at the end) or as a detached process with at (at now <<< "./pipeline some_script")

#!/bin/bash -Eue

# Using command name as the pipeline name
pipeline=$(basename $(expr "$1" : '\(^[^[:space:]]*\)')).pipe
is_reader=false

function _pipeline_cleanup {
        if $is_reader; then
                rm -f $pipeline
        fi
        rm -f $pipeline.lock

        exit
}
trap _pipeline_cleanup INT TERM EXIT

# Dispatch/initialization section, critical
lockfile $pipeline.lock
        if [[ -p $pipeline ]]
        then
                echo "$*" > $pipeline
                exit
        fi

        is_reader=true
        mkfifo $pipeline
        echo "$*" > $pipeline &
rm -f $pipeline.lock

# Reader section
while read command < $pipeline
do
        echo "$(date) - Executing $command"
        ($command) &> /dev/null
done