Final answer:
Use the 'where' command in Windows or the 'which' command in Unix/Linux to identify duplicate commands that are internal and external. These commands search the system's path and display all instances of the specified command.
Step-by-step explanation:
To determine if there are any duplicate commands that are internal (built-in to the shell) and external (separate executable files), we can use the 'where' command in Windows Command Prompt or the 'which' command in Unix/Linux shell. These commands will search the system's path to find all instances of the specified command and show where they are located, allowing you to identify duplicates. For instance, if you type 'where command-name' in Command Prompt or 'which command-name' in Unix/Linux terminal, it will list all paths where command-name can be found. These tools are useful for troubleshooting when a command isn't behaving as expected and you suspect a naming conflict.