The cron command is the clock daemon that executes commands at specified dates and times.
Question: I developed my script and it runs flawlessly, but when I insert it into the crontab, it fails.
Answer: The cron is executing with the root user id, and your environment is not set up correctly.
Fix: Investigate the use of the user cron feature or use the su command to execute your script. See man su. Essentially cron runs your script under the environment of a user.
Applications and user developed scripts should never be run under root, as they should have their own user environment.
If the script is very complex, you can set up a special user, and code the script in the user profile, then simply log into that user to execute. cron entry simply would be su - <user>. If you look at some of the UNIX special users, you will notice that the OS does it this way.