Which command is useful for concatenating and displaying the content of files?

The command that is useful for concatenating and displaying the content of files is "cat." This command stands for "concatenate" and it allows users to view the content of one or more files directly in the terminal. When you run "cat" followed by the names of the files, it outputs the contents sequentially, making it easy to read or pipe the output to other commands.

For example, using "cat file1.txt file2.txt" would display the contents of both files one after the other in the terminal window. Additionally, "cat" can be used to create new files or combine multiple files into a single file using redirection.

The other commands serve different purposes: "grep" is primarily used for searching through text based on patterns, "find" is designed to search for files and directories in a filesystem, and "echo" is used to output text or variables to the terminal. These functionalities are distinct from the capability of "cat" to concatenate and display file contents.