Append yyyyMMdd-HHmmss datetime to the filename on Linux

• 1 "filename-$(date +'%Y%m%d-%H%M%S').txt"
  
• N %Y four digits year
  %m zero-padded month
  %d zero-padded day
  %H zero-padded 24-hour
  %M zero-padded minute
  %S zero-padded second
  

References

• https://man7.org/linux/man-pages/man1/date.1.html
• https://www.redhat.com/sysadmin/formatting-date-command