The mv command can be used to rename files in UNIX. Here is the syntax:
mv old_filename new_filename
Here, old_filename is the name of the file you want to rename, and new_filename is the new name you want to give to the file.
For example, to rename a file named file1.txt to newfile.txt, you would use the following command:
mv file1.txt newfile.txt
This would rename the file file1.txt to newfile.txt.