Here will be some useful examples and snippet

• Bash single quotes and double quotes: https://askubuntu.com/a/605440
• lockrun: http://www.unixwiz.net/tools/lockrun.html
• solo: https://www.timkay.com/solo/
• Prevent CRON from overlapping: https://ma.ttias.be/prevent-cronjobs-from-overlapping-in-linux/
• bash colors: https://stackoverflow.com/a/28938235/4485894

# sh -x some-script-name.sh

Single quotes won't interpolate anything, but double quotes will. For example: variables, backticks, certain \ escapes, etc.

$ echo "$(echo "upg")"
upg
$ echo '$(echo "upg")'
$(echo "upg")