For searching text within a file or STDIN in Linux, which command should you use?

• A. grep
• B. ls
• C. mv
• D. cat

Answer: (A)

The command that is most effective for searching text within a file or standard input (STDIN) in Linux is grep. This command is specifically designed to search for patterns within text files and can be utilized with regular expressions for more complex search criteria. When you invoke grep, you specify a search pattern followed by one or more files to search through, or you can pipe output from another command into grep, allowing you to filter results based on the specified pattern.

In contrast, the other commands serve different purposes: listing files in a directory is done with ls, moving files from one location to another is accomplished with mv, and displaying the content of files is managed by cat. None of these commands have the built-in functionality required for searching text efficiently within a file or STDIN, making grep the appropriate choice for such tasks.